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Sample records for high ct numbers

  1. CT number variations in micro CT imaging systems

    NASA Astrophysics Data System (ADS)

    Tu, Shu-Ju; Hsieh, Hui-Ling; Chao, Tsi-Chian

    2008-03-01

    CT numbers can be directly computed from the linear attenuation coefficients in the reconstructed CT images and are correlated to the electron densities of the chemical elements with specific atomic numbers. However, the computed CT numbers can be varied when different imaging parameters are used. Phantoms composed of clinically relevant and tissue-equivalent materials (lung, bone, muscle, and adipose) were scanned with a commercial circular-scanning micro CT imager. This imaging system is composed with a micro-focused x-ray tube and charged-coupled device (CCD) camera as the detector. The mean CT numbers and the corresponding standard deviations in terms of Hounsfield units were then computed from a pre-defined region of interest located within the reconstructed volumetric images. The variations of CT number were then identified from a series of imaging parameters. Those parameters include imaging acquisition modes (e.g., the metal filter used in the x-ray tube), reconstruction methods (e.g., Feldkamp and iterative algorithm), and post-image processing techniques (e.g., ring artifact, beam-hardening artifact, and smoothing processing). These variations of CT numbers are useful and important in tissue characterization, quantitative bone structure analysis, bone marrow density evaluation, and Monte Carlo dose calculations for the pilot small animal study when micro CT imaging systems are employed. Also these variations can be used as the quantification for the performance of the micro CT imaging systems.

  2. Ion Stopping Powers and CT Numbers

    SciTech Connect

    Moyers, Michael F.; Sardesai, Milind; Sun, Sean; Miller, Daniel W.

    2010-10-01

    One of the advantages of ion beam therapy is the steep dose gradient produced near the ion's range. Use of this advantage makes knowledge of the stopping powers for all materials through which the beam passes critical. Most treatment planning systems calculate dose distributions using depth dose data measured in water and an algorithm that converts the kilovoltage X-ray computed tomography (CT) number of a given material to its linear stopping power relative to water. Some materials present in kilovoltage scans of patients and simulation phantoms do not lie on the standard tissue conversion curve. The relative linear stopping powers (RLSPs) of 21 different tissue substitutes and positioning, registration, immobilization, and beamline materials were measured in beams of protons accelerated to energies of 155, 200, and 250 MeV; carbon ions accelerated to 290 MeV/n; and iron ions accelerated to 970 MeV/n. These same materials were scanned with both kilovoltage and megavoltage CT scanners to obtain their CT numbers. Measured RLSPs and CT numbers were compared with calculated and/or literature values. Relationships of RLSPs to physical densities, electronic densities, kilovoltage CT numbers, megavoltage CT numbers, and water equivalence values converted by a treatment planning system are given. Usage of CT numbers and substitution of measured values into treatment plans to provide accurate patient and phantom simulations are discussed.

  3. Energy Dependence of Measured CT Numbers on Substituted Materials Used for CT Number Calibration of Radiotherapy Treatment Planning Systems

    PubMed Central

    Mahmoudi, Reza; Jabbari, Nasrollah; aghdasi, Mehdi; Khalkhali, Hamid Reza

    2016-01-01

    Introduction For accurate dose calculations, it is necessary to provide a correct relationship between the CT numbers and electron density in radiotherapy treatment planning systems (TPSs). The purpose of this study was to investigate the energy dependence of measured CT numbers on substituted materials used for CT number calibration of radiotherapy TPSs and the resulting errors in the treatment planning calculation doses. Materials and Methods In this study, we designed a cylindrical water phantom with different materials used as tissue equivalent materials for the simulation of tissues and obtaining the related CT numbers. For evaluating the effect of CT number variations of substituted materials due to energy changing of scanner (kVp) on the dose calculation of TPS, the slices of the scanned phantom at three kVp's were imported into the desired TPSs (MIRS and CorePLAN). Dose calculations were performed on two TPSs. Results The mean absolute percentage differences between the CT numbers of CT scanner and two treatment planning systems for all the samples were 3.22%±2.57% for CorePLAN and 2.88%±2.11% for MIRS. It was also found that the maximum absolute percentage difference between all of the calculated doses from each photon beam of linac (6 and 15 MV) at three kVp's was less than 1.2%. Discussion The present study revealed that, for the materials with effective low atomic number, the mean CT number increased with increasing energy, which was opposite for the materials with an effective high atomic number. We concluded that the tissue substitute materials had a different behavior in the energy ranges from 80 to 130 kVp. So, it is necessary to consider the energy dependence of the substitute materials used for the measurement or calibration of CT number for radiotherapy treatment planning systems. PMID:27391672

  4. Technical Note: Exploring the limit for the conversion of energy-subtracted CT number to electron density for high-atomic-number materials

    SciTech Connect

    Saito, Masatoshi; Tsukihara, Masayoshi

    2014-07-15

    Purpose: For accurate tissue inhomogeneity correction in radiotherapy treatment planning, the authors had previously proposed a novel conversion of the energy-subtracted CT number to an electron density (ΔHU–ρ{sub e} conversion), which provides a single linear relationship between ΔHU and ρ{sub e} over a wide ρ{sub e} range. The purpose of this study is to address the limitations of the conversion method with respect to atomic number (Z) by elucidating the role of partial photon interactions in the ΔHU–ρ{sub e} conversion process. Methods: The authors performed numerical analyses of the ΔHU–ρ{sub e} conversion for 105 human body tissues, as listed in ICRU Report 46, and elementary substances with Z = 1–40. Total and partial attenuation coefficients for these materials were calculated using the XCOM photon cross section database. The effective x-ray energies used to calculate the attenuation were chosen to imitate a dual-source CT scanner operated at 80–140 kV/Sn under well-calibrated and poorly calibrated conditions. Results: The accuracy of the resultant calibrated electron density,ρ{sub e}{sup cal}, for the ICRU-46 body tissues fully satisfied the IPEM-81 tolerance levels in radiotherapy treatment planning. If a criterion of ρ{sub e}{sup cal}/ρ{sub e} − 1 is assumed to be within ±2%, the predicted upper limit of Z applicable for the ΔHU–ρ{sub e} conversion under the well-calibrated condition is Z = 27. In the case of the poorly calibrated condition, the upper limit of Z is approximately 16. The deviation from the ΔHU–ρ{sub e} linearity for higher Z substances is mainly caused by the anomalous variation in the photoelectric-absorption component. Conclusions: Compensation among the three partial components of the photon interactions provides for sufficient linearity of the ΔHU–ρ{sub e} conversion to be applicable for most human tissues even for poorly conditioned scans in which there exists a large variation of effective x

  5. Fabrication and control of CT number through polymeric composites based on coronary plaque CT phantom applications.

    PubMed

    Hoy, Carlton F O; Naguib, Hani E; Paul, Narinder

    2016-01-01

    Biomedical phantoms are commonly used for various medical imaging modalities to improve imaging quality and procedures. Current biomedical phantoms fabricated commercially are high in cost and limited in the specificity of human environments and structures that can be mimicked. This study aimed to control the measurable computed tomography (CT) number in Hounsfield units through polymeric biomedical phantom materials using controlled amounts of hydroxyapatite (hA). The purpose was to fabricate CT phantoms capable of mimicking various coronary plaque types while introducing a fabrication technique and basis for a numerical model to which the technique may be applied. The CT number is tunable based on the controlled material properties of electron density and atomic numbers. Three different polymeric matrices of polyethylene (PE), thermoplastic polyurethane (TPU), and polyvinylidene fluoride (PVDF) were selected due to their varied specific densities and ease of fabrication acting as integral properties for CT phantom fabrication. These polymers were processed together with additions of hA in mass percentages of 2.5, 5, 10, and 20% hA as well as a 0% hA as a control for each polymeric material. By adding hA to PE, TPU, and PVDF an increasing trend was exhibited between CT number and weight percent of hA. PMID:26958580

  6. Thyroid CT number and its relationship to iodine concentration

    SciTech Connect

    Iida, Y.; Konishi, J.; Harioka, T.; Misaki, T.; Endo, K.; Torizuka, K.

    1983-06-01

    Sixty-seven patients with thyroid disease and 24 normal controls were examined with computed tomography (CT). The mean CT number (Hounsfield units +/- SD) in the normal controls (118.1 +/- 12.2) was significantly higher (p < 0.001) than the mean CT number in patients with diseased thyroids, except for 2 cases of simple goiter (CT numbers 113, 132). The Graves disease (69.5 +/- 17.6) amd Hishimoto thyroiditis (61.4 +/- 9.1) were significaantly higher than those in patients with adenoma (41.7 +/- 10.6, p < 0.001), cyst (33.1 +/- 14.8, p < 0.001), or cancer (48.7 +/- 13, p < 0.01). In 14 patients studied, a significant correlation was observed between thyroid CT numbers and the iodine concentration of the tissue (r = 0.889; p < 0.001).

  7. High Reynolds Number Research

    NASA Technical Reports Server (NTRS)

    Baals, D. D. (Editor)

    1977-01-01

    Fundamental aerodynamic questions for which high Reynolds number experimental capability is required are discussed. The operational characteristics and design features of the National Transonic Facility are reviewed.

  8. 75 FR 29590 - Connecticut Disaster Number CT-00015

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-26

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00015 AGENCY: Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for Public...

  9. 78 FR 7848 - Connecticut Disaster Number CT-00028

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-04

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00028 AGENCY: U.S. Small Business Administration. ACTION: Amendment...: U.S. Small Business Administration, Processing and Disbursement Center, 14925 Kingsport Road,...

  10. 76 FR 58329 - Connecticut Disaster Number CT-00024

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-20

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00024 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the...

  11. 77 FR 76587 - Connecticut Disaster Number CT-00028

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-28

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00028 AGENCY: U.S. Small Business Administration. ACTION: Amendment 2. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the...

  12. 76 FR 58559 - Connecticut Disaster Number CT-00023

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-21

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00023 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for...

  13. 77 FR 71665 - Connecticut Disaster Number CT-00028

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-03

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00028 AGENCY: U.S. Small Business Administration. ACTION: Amendment 1. SUMMARY: This is an amendment of the Presidential declaration of a major disaster for the...

  14. TU-F-18A-09: CT Number Stability Across Patient Sizes Using Virtual-Monoenergetic Dual-Energy CT

    SciTech Connect

    Michalak, G; Grimes, J; Fletcher, J; McCollough, C; Halaweish, A

    2014-06-15

    Purpose: Virtual-monoenergetic imaging uses dual-energy CT data to synthesize images corresponding to a single photon energy, thereby reducing beam-hardening artifacts. This work evaluated the ability of a commercial virtual-monoenergetic algorithm to achieve stable CT numbers across patient sizes. Methods: Test objects containing a range of iodine and calcium hydroxyapatite concentrations were placed inside 8 torso-shaped water phantoms, ranging in lateral width from 15 to 50 cm, and scanned on a dual-source CT system (Siemens Somatom Force). Single-energy scans were acquired from 70-150 kV in 10 kV increments; dual-energy scans were acquired using 4 energy pairs (low energy: 70, 80, 90, and 100 kV; high energy: 150 kV + 0.6 mm Sn). CTDIvol was matched for all single- and dual-energy scans for a given phantom size. All scans used 128×0.6 mm collimation and were reconstructed with 1-mm thickness at 0.8-mm increment and a medium smooth body kernel. Monoenergetic images were generated using commercial software (syngo Via Dual Energy, VA30). Iodine contrast was calculated as the difference in mean iodine and water CT numbers from respective regions-of-interest in 10 consecutive images. Results: CT numbers remained stable as phantom width varied from 15 to 50 cm for all dual-energy data sets (except for at 50 cm using 70/150Sn due to photon starvation effects). Relative to the 15 cm phantom, iodine contrast was within 5.2% of the 70 keV value for phantom sizes up to 45 cm. At 90/150Sn, photon starvation did not occur at 50 cm, and iodine contrast in the 50-cm phantom was within 1.4% of the 15-cm phantom. Conclusion: Monoenergetic imaging, as implemented in the evaluated commercial system, eliminated the variation in CT numbers due to patient size, and may provide more accurate data for quantitative tasks, including radiation therapy treatment planning. Siemens Healthcare.

  15. High Reynolds number research - 1980

    NASA Technical Reports Server (NTRS)

    Mckinney, L. W. (Editor); Baals, D. D. (Editor)

    1981-01-01

    The fundamental aerodynamic questions for which high Reynolds number experimental capability is required were examined. Potential experiments which maximize the research returns from the use of the National Transonic Facility (NTF) were outlined. Calibration plans were reviewed and the following topics were discussed: fluid dynamics; high lit; configuration aerodynamics; aeroelasticity and unsteady aerodynamics; wind tunnel/flight correlation; space vehicles; and theoretical aerodynamics

  16. Accuracies of the synthesized monochromatic CT numbers and effective atomic numbers obtained with a rapid kVp switching dual energy CT scanner

    SciTech Connect

    Goodsitt, Mitchell M.; Christodoulou, Emmanuel G.; Larson, Sandra C.

    2011-04-15

    Purpose: This study was performed to investigate the accuracies of the synthesized monochromatic images and effective atomic number maps obtained with the new GE Discovery CT750 HD CT scanner. Methods: A Gammex-RMI model 467 tissue characterization phantom and the CT number linearity section of a Phantom Laboratory Catphan 600 phantom were scanned using the dual energy (DE) feature on the GE CT750 HD scanner. Synthesized monochromatic images at various energies between 40 and 120 keV and effective atomic number (Z{sub eff}) maps were generated. Regions of interest were placed within these images/maps to measure the average monochromatic CT numbers and average Z{sub eff} of the materials within these phantoms. The true Z{sub eff} values were either supplied by the phantom manufacturer or computed using Mayneord's equation. The linear attenuation coefficients for the true CT numbers were computed using the NIST XCOM program with the input of manufacturer supplied elemental compositions and densities. The effects of small variations in the assumed true densities of the materials were also investigated. Finally, the effect of body size on the accuracies of the synthesized monochromatic CT numbers was investigated using a custom lumbar section phantom with and without an external fat-mimicking ring. Results: Other than the Z{sub eff} of the simulated lung inserts in the tissue characterization phantom, which could not be measured by DECT, the Z{sub eff} values of all of the other materials in the tissue characterization and Catphan phantoms were accurate to 15%. The accuracies of the synthesized monochromatic CT numbers of the materials in both phantoms varied with energy and material. For the 40-120 keV range, RMS errors between the measured and true CT numbers in the Catphan are 8-25 HU when the true CT numbers were computed using the nominal plastic densities. These RMS errors improve to 3-12 HU for assumed true densities within the nominal density {+-}0.02 g

  17. An assessment of image distortion and CT number accuracy within a wide-bore CT extended field of view.

    PubMed

    Beeksma, B; Truant, D; Holloway, L; Arumugam, S

    2015-06-01

    Although wide bore computed tomography (CT) scanners provide increased space for patients, the scan field of view (sFOV) remains considerably smaller than the bore size. Consequently, patient anatomy which spans beyond the sFOV is truncated and the information is lost. As a solution, some manufacturers provide the capacity to reconstruct CT images from a partial dataset at an extended field of view (eFOV). To assess spatial distortion within this eFOV three phantoms were considered a 30 × 30 × 20 cm(3) slab of solid water, the Gammex electron density CT phantom and a female anthropomorphic phantom. For each phantom, scans were taken centrally within the sFOV as a reference image and with the phantom edge extended at 1 cm intervals from 0 to 5 cm beyond the sFOV into the eFOV. To assess CT number accuracy various tissue equivalent materials were scanned in the eFOV and resulting CT numbers were compared to inserts scanned within the sFOV. For all phantom geometries, objects within the eFOV were geometrically overestimated with elongation of phantom shapes into the eFOV. The percentage increase in size ranged from 0.22 to 15.94 % over all phantoms considered. The difference between eFOV and sFOV CT numbers was dependent upon insert density. The eFOV underestimated CT numbers in the range of -127 to -230 HU for soft tissue densities and -278 to -640 for bone densities. This trend reversed for low tissue densities with the CT numbers in the eFOV being overestimated by 100-130 HU for lung equivalent inserts. Initial correlation between eFOV and sFOV CT numbers was seen and a correction function was successfully applied to better estimate the CT number representative of that seen within the sFOV. PMID:26048719

  18. High resolution extremity CT for biomechanics modeling

    SciTech Connect

    Ashby, A.E.; Brand, H.; Hollerbach, K.; Logan, C.M.; Martz, H.E.

    1995-09-23

    With the advent of ever more powerful computing and finite element analysis (FEA) capabilities, the bone and joint geometry detail available from either commercial surface definitions or from medical CT scans is inadequate. For dynamic FEA modeling of joints, precise articular contours are necessary to get appropriate contact definition. In this project, a fresh cadaver extremity was suspended in parafin in a lucite cylinder and then scanned with an industrial CT system to generate a high resolution data set for use in biomechanics modeling.

  19. Quasiperpendicular High Mach Number Shocks.

    PubMed

    Sulaiman, A H; Masters, A; Dougherty, M K; Burgess, D; Fujimoto, M; Hospodarsky, G B

    2015-09-18

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (M_{A}) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ~0.3τ_{c}, where τ_{c} is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and M_{A} and focus on the magnetic structure of such shocks to further show that for the same M_{A}, a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming. PMID:26430997

  20. Quasiperpendicular High Mach Number Shocks

    NASA Astrophysics Data System (ADS)

    Sulaiman, A. H.; Masters, A.; Dougherty, M. K.; Burgess, D.; Fujimoto, M.; Hospodarsky, G. B.

    2015-09-01

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (MA ) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ˜0.3 τc , where τc is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA , a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.

  1. Petrous apex mucocele: high resolution CT.

    PubMed

    Memis, A; Memis, A; Alper, H; Calli, C; Ozer, H; Ozdamar, N

    1994-11-01

    Mucocele of the petrous apex is very rare, only three cases having been reported. Since this area is inaccessible to direct examination, imaging, preferably high resolution computed tomography (HR CT) is essential. We report a case showing an eroding, non enhancing mass with sharp, lobulated contours, within the petrous apex. The presence of a large air cell on the opposite side suggested a mucocele. PMID:7862284

  2. Evaluation of a bilinear model for attenuation correction using CT numbers generated from a parametric method.

    PubMed

    Martinez, L C; Calzado, A

    2016-01-01

    A parametric model is used for the calculation of the CT number of some selected human tissues of known compositions (Hi) in two hybrid systems, one SPECT-CT and one PET-CT. Only one well characterized substance, not necessarily tissue-like, needs to be scanned with the protocol of interest. The linear attenuation coefficients of these tissues for some energies of interest (μ(i)) have been calculated from their tabulated compositions and the NIST databases. These coefficients have been compared with those calculated with the bilinear model from the CT number (μ(B)i). No relevant differences have been found for bones and lung. In the soft tissue region, the differences can be up to 5%. These discrepancies are attributed to the different chemical composition for the tissues assumed by both methods. PMID:26454019

  3. Comparison of CT numbers of organs before and after plastination using standard S-10 technique.

    PubMed

    Shanthi, Pauline; Singh, Rabi Raja; Gibikote, Sridhar; Rabi, Suganthy

    2015-05-01

    Plastination is the art of preserving biological tissues with curable polymers. Imaging with plastinates offers a unique opportunity for radiographic, anatomical, pathological correlation to elucidate complex anatomical relationships. The aim of this study was to make plastinates from cadavers using the standard S-10 plastination technique and to compare the radiological properties of the tissue before and afterwards to examine the suitability of plastinates as phantoms for planning radiotherapy treatment. An above-diaphragm and a below-diaphragm specimen were obtained from a male and a female cadaver, respectively, and subjected to the standard S-10 plastination technique. CT images were obtained before and after plastination and were compared using Treatment Planning System for anatomical accuracy, volume of organs, and CT numbers. The plastinated specimens obtained were dry, robust, and durable. CT imaging of the plastinated specimens showed better anatomical detail of the organs than the preplastinate. Organ volumes were estimated by contouring the organs' outline in the CT images of the preplastinated and postplastinated specimens, revealing an average shrinkage of 25%. CT numbers were higher in the plastinated specimens except in bones and air-filled cavities such as the maxillary air sinus. Although plastination by the standard S-10 technique preserves anatomical accuracy, it increases the CT numbers of the organs because of the density of silicone, making it unsuitable for radiation dosimetry. Further improvements of the technique could yield more suitable plastinated phantoms. PMID:25708008

  4. Quantitative imaging of electron density and effective atomic number using phase contrast CT

    NASA Astrophysics Data System (ADS)

    Qi, Zhihua; Zambelli, Joseph; Bevins, Nicholas; Chen, Guang-Hong

    2010-05-01

    Compared to single energy CT, which only provides information for x-ray linear attenuation coefficients, dual-energy CT is able to obtain both the electron density and effective atomic number for different materials in a quantitative way. In this study, as an alternative to dual-energy CT, a novel quantitative imaging method based on phase contrast CT is presented. Rather than requiring two projection data sets with different x-ray energy spectra, diffraction-grating-based phase contrast CT is capable of reconstructing images of both linear attenuation and refractive index decrement from the same projection data using a single x-ray energy spectra. From the two images, quantitative information of both the electron density and effective atomic number can be extracted. Two physical phantoms were constructed and used to validate the presented method. Experimental results demonstrate that (1) electron density can be accurately determined from refractive index decrement through a linear relationship, and (2) the effective atomic number can be explicitly derived from the ratio of the linear attenuation to refractive index decrement using a power function plus a constant. The presented method will provide insight into the technique of material separation and find its use in medical and industrial applications.

  5. CT Hounsfield Numbers of Soft Tissues on Unenhanced Abdominal CT Scans: Variability Between Two Different Manufacturers’ MDCT Scanners

    PubMed Central

    Lamba, Ramit; McGahan, John P.; Corwin, Michael T.; Li, Chin-Shang; Tran, Tien; Seibert, J. Anthony; Boone, John M.

    2016-01-01

    OBJECTIVE The purpose of this study is to determine whether Hounsfield numbers of soft tissues on unenhanced abdominal CT of the same patient vary on repeat scans done on two different manufacturers’ MDCT scanners. MATERIALS AND METHODS A database search was performed to identify patients older than 18 years who underwent unenhanced CT of the abdomen and pelvis performed both on a Volume CT (GE Healthcare) and a Definition AS Plus (Siemens Healthcare) 64-MDCT scanner within 12 months of each other. After excluding those patients for whom Hounsfield unit measurements would be affected by mitigating factors, 48 patients (mean age, 58.8 years) were identified. Hounsfield unit measurements were obtained in nine different soft-tissue anatomic locations on each scan, and the location of these sites was kept identical on each scan pair. Data were analyzed to evaluate Hounsfield unit differences between these scanners. RESULTS In general, there was a low consistency in the Hounsfield unit measurements for each of these sites on scans obtained by the two scanners, with the subcutaneous fat in the left posterolateral flank showing the lowest correlation (intraclass correlation coefficient, 0.198). There were differences in the Hounsfield unit measurements obtained in all anatomic sites on scans obtained by both scanners. Mean Hounsfield unit measurements obtained on the Definition AS Plus scanner were lower than those obtained on the Volume CT scanner, with the intriguing exception of the anterior midline subcutaneous fat Hounsfield unit measurements, which were higher on the Definition AS Plus scanner. All differences were statistically significant (p < 0.05). CONCLUSION Hounsfield unit measurements for unenhanced abdominal soft tissues of the same patient vary between scanners of two common MDCT manufacturers. PMID:25341139

  6. Tomosynthesis using high speed CT scanning system

    SciTech Connect

    Boyd, D.P.; Rutt, B.K.

    1988-04-05

    In a high-speed CT scanning system in which fan beams of radiation are generated by sweeping an electron beam along a target and collimated X-rays emitted by the target are received by an array of detectors after passing through a patient area between the target and the array of detectors, a method of obtaining a tomograph of a patient is described comprising the steps of sweeping the electron beam along the target, measuring radiation received at detector positions as the electron beam is swept along the target; moving the patient past the collimated X-rays, and combining measurements at the detector positions as correlated in time to positions of the patient and tomosynthesizing the tomograph from data for lines in the desired plane for the positions of the patient.

  7. SU-E-J-272: Auto-Segmentation of Regions with Differentiating CT Numbers for Treatment Response Assessment

    SciTech Connect

    Yang, C; Noid, G; Dalah, E; Paulson, E; Li, X; Gilat-Schmidt, T

    2015-06-15

    Purpose: It has been reported recently that the change of CT number (CTN) during and after radiation therapy (RT) may be used to assess RT response. The purpose of this work is to develop a tool to automatically segment the regions with differentiating CTN and/or with change of CTN in a series of CTs. Methods: A software tool was developed to identify regions with differentiating CTN using K-mean Cluster of CT numbers and to automatically delineate these regions using convex hull enclosing method. Pre- and Post-RT CT, PET, or MRI images acquired for sample lung and pancreatic cancer cases were used to test the software tool. K-mean cluster of CT numbers within the gross tumor volumes (GTVs) delineated based on PET SUV (standard uptake value of fludeoxyglucose) and/or MRI ADC (apparent diffusion coefficient) map was analyzed. The cluster centers with higher value were considered as active tumor volumes (ATV). The convex hull contours enclosing preset clusters were used to delineate these ATVs with color washed displays. The CTN defined ATVs were compared with the SUV- or ADC-defined ATVs. Results: CTN stability of the CT scanner used to acquire the CTs in this work is less than 1.5 Hounsfield Unit (HU) variation annually. K-mean cluster centers in the GTV have difference of ∼20 HU, much larger than variation due to CTN stability, for the lung cancer cases studied. The dice coefficient between the ATVs delineated based on convex hull enclosure of high CTN centers and the PET defined GTVs based on SUV cutoff value of 2.5 was 90(±5)%. Conclusion: A software tool was developed using K-mean cluster and convex hull contour to automatically segment high CTN regions which may not be identifiable using a simple threshold method. These CTN regions were reasonably overlapped with the PET or MRI defined GTVs.

  8. Dependence Of The Computerized Tomography (CT) Number - Electron Density Relationship On Patient Size And X-Ray Beam Filtration For Fan Beam CT Scanners

    NASA Astrophysics Data System (ADS)

    Masterson, M. E.; Thomason, C. L.; McGary, R.; Hunt, M. A.; Simpson, L. D.; Miller, D. W.; Laughlin, J. S.

    1981-07-01

    The applicability of quantitative information contained in CT scans to diagnostic radiology and to radiation therapy treatment planning and the heterogeneity problem has been recognized by members of the radiological community and by manufacturers. Determination of the relationship between electron density and CT number is important for these applications. As CT technology has evolved, CT number generation has changed. CT number variation was limited in the early water bag systems. However, later generation "air" scanners may exhibit variation in CT numbers across a reconstructed image which are re-lated to positioning within the scan circle and scan field size. Results of experimental investigations using tissue-equivalent phantoms of different cross-sectional shapes and areas on the Technicare Delta 2020 are presented. Investigations also cover the effect of "shaped" and "flat" x-ray beam filters. A variation in CT number is demonstrated on this fan beam geometry scanner for phantoms of different sizes and for different scan circle diameters. An explanation of these effects is given. Differences of as much as 20% in determination of tissue electron density relative to water under different experimental conditions are obtained and reported. A family of curves (electron density vs. CT number) is presented for different patient cross-sectional areas and different scanner settings.

  9. Highly accurate fast lung CT registration

    NASA Astrophysics Data System (ADS)

    Rühaak, Jan; Heldmann, Stefan; Kipshagen, Till; Fischer, Bernd

    2013-03-01

    Lung registration in thoracic CT scans has received much attention in the medical imaging community. Possible applications range from follow-up analysis, motion correction for radiation therapy, monitoring of air flow and pulmonary function to lung elasticity analysis. In a clinical environment, runtime is always a critical issue, ruling out quite a few excellent registration approaches. In this paper, a highly efficient variational lung registration method based on minimizing the normalized gradient fields distance measure with curvature regularization is presented. The method ensures diffeomorphic deformations by an additional volume regularization. Supplemental user knowledge, like a segmentation of the lungs, may be incorporated as well. The accuracy of our method was evaluated on 40 test cases from clinical routine. In the EMPIRE10 lung registration challenge, our scheme ranks third, with respect to various validation criteria, out of 28 algorithms with an average landmark distance of 0.72 mm. The average runtime is about 1:50 min on a standard PC, making it by far the fastest approach of the top-ranking algorithms. Additionally, the ten publicly available DIR-Lab inhale-exhale scan pairs were registered to subvoxel accuracy at computation times of only 20 seconds. Our method thus combines very attractive runtimes with state-of-the-art accuracy in a unique way.

  10. Number Theory in the High School Classroom.

    ERIC Educational Resources Information Center

    Dence, Thomas

    1999-01-01

    Demonstrates some of the usefulness of number theory to students on the high school setting in four areas: Fibonacci numbers, Diophantine equations, continued fractions, and algorithms for computing pi. (ASK)

  11. Potential of dual-energy subtraction for converting CT numbers to electron density based on a single linear relationship

    SciTech Connect

    Saito, Masatoshi

    2012-04-15

    Purpose: The conversion of the computed tomography (CT) number to electron density is one of the main processes that determine the accuracy of patient dose calculations in radiotherapy treatment planning. However, the CT number and electron density of tissues cannot be generally interrelated via a simple one-to-one correspondence because the CT number depends on the effective atomic number as well as the electron density. The purpose of this study is to present a simple conversion from the energy-subtracted CT number ({Delta}HU) by means of dual-energy CT (DECT) to the relative electron density ({rho}{sub e}) via a single linear relationship. Methods: The {Delta}HU-{rho}{sub e} conversion method was demonstrated by performing analytical DECT image simulations that were intended to imitate a second-generation dual-source CT (DSCT) scanner with an additional tin filtration for the high-kV tube. The {Delta}HU-{rho}{sub e} calibration line was obtained from the image simulation with a 33 cm-diameter electron density calibration phantom equipped with 16 inserts including polytetrafluoroethylene, polyvinyl chloride, and aluminum; the elemental compositions of these three inserts were quite different to those of body tissues. The {Delta}HU-{rho}{sub e} conversion method was also applied to previously published experimental CT data, which were measured using two different CT scanners, to validate the clinical feasibility of the present approach. In addition, the effect of object size on {rho}{sub e}-calibrated images was investigated by image simulations using a 25 cm-diameter virtual phantom for two different filtrations: with and without the tin filter for the high-kV tube. Results: The simulated {Delta}HU-{rho}{sub e} plot exhibited a predictable linear relationship over a wide range of {rho}{sub e} from 0.00 (air) to 2.35 (aluminum). Resultant values of the coefficient of determination, slope, and intercept of the linear function fitted to the data were close to those

  12. CT and Ultrasound Guided Stereotactic High Intensity Focused Ultrasound (HIFU)

    SciTech Connect

    Wood, Bradford J.; Frenkel, V.; Viswanathan, A.; Dromi, S.; Oh, K.; Kam, A.; Li, K. C. P.; Yanof, J.; Bauer, C.; Kruecker, J.; Seip, R.

    2006-05-08

    To demonstrate the feasibility of CT and B-mode Ultrasound (US) targeted HIFU, a prototype coaxial focused ultrasound transducer was registered and integrated to a CT scanner. CT and diagnostic ultrasound were used for HIFU targeting and monitoring, with the goals of both thermal ablation and non-thermal enhanced drug delivery. A 1 megahertz coaxial ultrasound transducer was custom fabricated and attached to a passive position-sensing arm and an active six degree-of-freedom robotic arm via a CT stereotactic frame. The outer therapeutic transducer with a 10 cm fixed focal zone was coaxially mounted to an inner diagnostic US transducer (2-4 megahertz, Philips Medical Systems). This coaxial US transducer was connected to a modified commercial focused ultrasound generator (Focus Surgery, Indianapolis, IN) with a maximum total acoustic power of 100 watts. This pre-clinical paradigm was tested for ability to heat tissue in phantoms with monitoring and navigation from CT and live US. The feasibility of navigation via image fusion of CT with other modalities such as PET and MRI was demonstrated. Heated water phantoms were tested for correlation between CT numbers and temperature (for ablation monitoring). The prototype transducer and integrated CT/US imaging system enabled simultaneous multimodality imaging and therapy. Pre-clinical phantom models validated the treatment paradigm and demonstrated integrated multimodality guidance and treatment monitoring. Temperature changes during phantom cooling corresponded to CT number changes. Contrast enhanced or non-enhanced CT numbers may potentially be used to monitor thermal ablation with HIFU. Integrated CT, diagnostic US, and therapeutic focused ultrasound bridges a gap between diagnosis and therapy. Preliminary results show that the multimodality system may represent a relatively inexpensive, accessible, and simple method of both targeting and monitoring HIFU effects. Small animal pre-clinical models may be translated to large

  13. CT and Ultrasound Guided Stereotactic High Intensity Focused Ultrasound (HIFU)

    NASA Astrophysics Data System (ADS)

    Wood, Bradford J.; Yanof, J.; Frenkel, V.; Viswanathan, A.; Dromi, S.; Oh, K.; Kruecker, J.; Bauer, C.; Seip, R.; Kam, A.; Li, K. C. P.

    2006-05-01

    To demonstrate the feasibility of CT and B-mode Ultrasound (US) targeted HIFU, a prototype coaxial focused ultrasound transducer was registered and integrated to a CT scanner. CT and diagnostic ultrasound were used for HIFU targeting and monitoring, with the goals of both thermal ablation and non-thermal enhanced drug delivery. A 1 megahertz coaxial ultrasound transducer was custom fabricated and attached to a passive position-sensing arm and an active six degree-of-freedom robotic arm via a CT stereotactic frame. The outer therapeutic transducer with a 10 cm fixed focal zone was coaxially mounted to an inner diagnostic US transducer (2-4 megahertz, Philips Medical Systems). This coaxial US transducer was connected to a modified commercial focused ultrasound generator (Focus Surgery, Indianapolis, IN) with a maximum total acoustic power of 100 watts. This pre-clinical paradigm was tested for ability to heat tissue in phantoms with monitoring and navigation from CT and live US. The feasibility of navigation via image fusion of CT with other modalities such as PET and MRI was demonstrated. Heated water phantoms were tested for correlation between CT numbers and temperature (for ablation monitoring). The prototype transducer and integrated CT/US imaging system enabled simultaneous multimodality imaging and therapy. Pre-clinical phantom models validated the treatment paradigm and demonstrated integrated multimodality guidance and treatment monitoring. Temperature changes during phantom cooling corresponded to CT number changes. Contrast enhanced or non-enhanced CT numbers may potentially be used to monitor thermal ablation with HIFU. Integrated CT, diagnostic US, and therapeutic focused ultrasound bridges a gap between diagnosis and therapy. Preliminary results show that the multimodality system may represent a relatively inexpensive, accessible, and simple method of both targeting and monitoring HIFU effects. Small animal pre-clinical models may be translated to large

  14. Effective atomic number accuracy for kidney stone characterization using spectral CT

    NASA Astrophysics Data System (ADS)

    Joshi, M.; Langan, D. A.; Sahani, D. S.; Kambadakone, A.; Aluri, S.; Procknow, K.; Wu, X.; Bhotika, R.; Okerlund, D.; Kulkarni, N.; Xu, D.

    2010-04-01

    The clinical application of Gemstone Spectral ImagingTM, a fast kV switching dual energy acquisition, is explored in the context of noninvasive kidney stone characterization. Utilizing projection-based material decomposition, effective atomic number and monochromatic images are generated for kidney stone characterization. Analytical and experimental measurements are reported and contrasted. Phantoms were constructed using stone specimens extracted from patients. This allowed for imaging of the different stone types under similar conditions. The stone specimens comprised of Uric Acid, Cystine, Struvite and Calcium-based compositions. Collectively, these stone types span an effective atomic number range of approximately 7 to 14. While Uric Acid and Calcium based stones are generally distinguishable in conventional CT, stone compositions like Cystine and Struvite are difficult to distinguish resulting in treatment uncertainty. Experimental phantom measurements, made under increasingly complex imaging conditions, illustrate the impact of various factors on measurement accuracy. Preliminary clinical studies are reported.

  15. Toward high-contrast breast CT at low radiation dose.

    PubMed

    Keyriläinen, Jani; Fernández, Manuel; Karjalainen-Lindsberg, Marja-Liisa; Virkkunen, Pekka; Leidenius, Marjut; von Smitten, Karl; Sipilä, Petri; Fiedler, Stefan; Suhonen, Heikki; Suortti, Pekka; Bravin, Alberto

    2008-10-01

    This study was approved by the local research ethics committee, and patient informed consent was obtained. The purpose of this study was to demonstrate that high-spatial-resolution low-dose analyzer-based x-ray computed tomography (CT) can substantially improve the radiographic contrast of breast tissue in vitro when compared with that attained by using diagnostic mammography and CT. An excised human breast tumor was examined by using analyzer-based x-ray imaging with synchrotron radiation. The correspondence between analyzer-based x-ray images and diagnostic mammograms, CT images, and histopathologic findings was determined. Calcifications and fine details of soft tissue, which are at the contrast detection limit on diagnostic mammograms, are clearly visible on planar analyzer-based x-ray images. Analyzer-based x-ray CT yields high contrast from smoothly varying internal structures, such as tumorous mass lesions, corresponding to information on actual structures seen at histopathologic analysis. The mean glandular dose of 1.9 mGy in analyzer-based x-ray CT is approximately equivalent to the dose administered during single-view screening mammography. The improved visibility of mammographically indistinguishable lesions in vitro suggests that analyzer-based x-ray CT may be a valuable method in radiographic evaluation of the breast, thereby justifying further investigations. PMID:18796684

  16. The effects of field-of-view and patient size on CT numbers from cone-beam computed tomography

    NASA Astrophysics Data System (ADS)

    Seet, Katrina Y. T.; Barghi, Arvand; Yartsev, Slav; Van Dyk, Jake

    2009-10-01

    Cone-beam computed tomography (CBCT) is used for patient alignment before treatment and is ideal for use in adaptive radiotherapy to account for tumor shrinkage, organ deformation and weight loss. However, CBCT images are prone to artifacts such as streaking and cupping effects, reducing image quality and CT number accuracy. Our goal was to determine the optimum combination of cone-beam imaging options to increase the accuracy of image CT numbers. Several phantoms with and without inserts of known relative electron densities were imaged using the Varian on-board imaging system. It was found that CT numbers are most influenced by the selection of field-of-view and are dependent on object size and filter type. Image acquisition in half-fan mode consistently produced more accurate CT numbers, regardless of phantom size. Values measured using full-fan mode can differ by up to 7% from planning CT values. No differences were found between CT numbers of all phantom images with low and standard dose modes.

  17. Decay of turbulence at high reynolds numbers.

    PubMed

    Sinhuber, Michael; Bodenschatz, Eberhard; Bewley, Gregory P

    2015-01-23

    Turbulent motions in a fluid decay at a certain rate once stirring has stopped. The role of the most basic parameter in fluid mechanics, the Reynolds number, in setting the decay rate is not generally known. This Letter concerns the high-Reynolds-number limit of the process. In a classical grid-turbulence wind-tunnel experiment that both reaches higher Reynolds numbers than ever before and covers a wide range of them (10^{4}number independent, which contradicts some models and supports others. PMID:25659002

  18. Chaotic behaviour of high Mach number flows

    NASA Technical Reports Server (NTRS)

    Varvoglis, H.; Ghosh, S.

    1985-01-01

    The stability of the super-Alfvenic flow of a two-fluid plasma model with respect to the Mach number and the angle between the flow direction and the magnetic field is investigated. It is found that, in general, a large scale chaotic region develops around the initial equilibrium of the laminar flow when the Mach number exceeds a certain threshold value. After reaching a maximum the size of this region begins shrinking and goes to zero as the Mach number tends to infinity. As a result high Mach number flows in time independent astrophysical plasmas may lead to the formation of 'quasi-shocks' in the presence of little or no dissipation.

  19. Decay of Turbulence at High Reynolds Numbers

    NASA Astrophysics Data System (ADS)

    Sinhuber, Michael; Bodenschatz, Eberhard; Bewley, Gregory P.

    2015-01-01

    Turbulent motions in a fluid decay at a certain rate once stirring has stopped. The role of the most basic parameter in fluid mechanics, the Reynolds number, in setting the decay rate is not generally known. This Letter concerns the high-Reynolds-number limit of the process. In a classical grid-turbulence wind-tunnel experiment that both reaches higher Reynolds numbers than ever before and covers a wide range of them (1 04number independent, which contradicts some models and supports others.

  20. X-ray CT high-density artefact suppression in the presence of bones

    NASA Astrophysics Data System (ADS)

    Wei, Jikun; Chen, Laigao; Sandison, George A.; Liang, Yun; Xu, Lisa X.

    2004-12-01

    This paper presents a novel method of reducing x-ray CT high-density artefacts generated by metal objects when abundant bone structures are present in the region of interest. This method has an advantage over previously proposed methods since it heavily suppresses the metal artefacts without introducing extra bone artefacts. The method of suppression requires that bone pixels are isolated and segmented by thresholding. Then artificial CT numbers are assigned to the bone pixels so that their projection profiles are smooth and thus can be properly simulated by a polynomial interpolation. The projection profile of the metal object is then removed to fully suppress the artefacts. The resulting processed profile is fed to a reconstruction routine and the previously preserved bone pixels added back. The new method utilizes two important features of the CT image with metal artefacts: (a) metal and bone pixels are not severely affected by the high-density artefacts and (b) the high-density artefacts can be located in specific projection channels in the profile domain, although they are spread out in the image domain. This suppression method solves the problem of CT image artefacts arising from metal objects in the body. It has the potential to greatly improve diagnostic CT imaging in the presence of these objects and treatment planning that utilizes CT for patients with metal applicators (e.g., brachytherapy for cervix cancer and prostate cryotherapy).

  1. High Reynolds Number Thermal Stability Experiments

    NASA Technical Reports Server (NTRS)

    Emens, Jessica M.; Brown, Sarah P.; Frederick Robert A., Jr.; Wood, A. John

    2004-01-01

    This work represents preliminary thermal stability results for liquid hydrocarbon fuels. High Reynolds Number Thermal Stability experiments with Jet A and RP-1 resulted in a quantitative measurement of the thermal stability. Each fuel flowed through a heated capillary tube that held the outlet temperature at 290 C. An optical pyrometer measured the surface temperature of the tube at 12 locations as a function of time. The High Reynolds Number Thermal Stability number was then determined using standards published by the American Society for Testing and Materials. The results for Jet A showed lower thermal stability than similar tests conducted at another facility. The RP-1 results are the first reported using this technique. Because the temperature rise on the capillary tube during testing for the RP-1 fuels was not significant, a new standard for the testing conditions should be developed for these types of fuels.

  2. Metrology, applications and methods with high energy CT systems

    SciTech Connect

    Uhlmann, N.; Voland, V.; Salamon, M.; Hebele, S.; Boehnel, M.; Reims, N.; Schmitt, M.; Kasperl, S.

    2014-02-18

    The increase of Computed Tomography (CT) as an applicable metrology and Non Destructive Testing (NDT) method raises interest on developing the application fields to larger objects, which were rarely used in the past due to their requirements on the imaging system. Especially the classical X-ray generation techniques based on standard equipment restricted the applications of CT to typical material penetration lengths of only a few cm of steel. Even with accelerator technology that offers a suitable way to overcome these restrictions just the 2D radioscopy technique found a widespread application. Beside the production and detection of photons in the MeV range itself, the achievable image quality is limited using standard detectors due to the dominating absorption effect of Compton Scattering at high energies. Especially for CT reconstruction purposes these effects have to be considered on the development path from 2D to 3D imaging. Most High Energy CT applications are therefore based on line detectors shielding scattered radiation to a maximum with an increase in imaging quality but with time consuming large volume scan capabilities. In this contribution we present the High-Energy X-ray Imaging project at the Fraunhofer Development Centre for X-ray Technology with the characterization and the potential of the CT-system according to metrological and other application capabilities.

  3. Comparison of CT-Number and Gray Scale Value of Different Dental Materials and Hard Tissues in CT and CBCT

    PubMed Central

    Emadi, Naghmeh; Safi, Yaser; Akbarzadeh Bagheban, Alireza; Asgary, Saeed

    2014-01-01

    Introduction: Computed tomography (CT) and cone-beam CT (CBCT) are valuable diagnostic aids for many clinical applications. This study was designed to compare the gray scale value (GSV) and Hounsfield unit (HU) of selected dental materials and various hard tissues using CT or CBCT. Methods and Materials: Three samples of all test materials including amalgam (AM), composite resin (CR), glass ionomer (GI), zinc-oxide eugenol (ZOE), calcium-enriched mixture (CEM) cement, AH-26 root canal sealer (AH-26), gutta-percha (GP), Coltosol (Col), Dycal (DL), mineral trioxide aggregate (MTA), zinc phosphate (ZP), and polycarbonate cement (PC) were prepared and scanned together with samples of bone, dentin and enamel using two CBCT devices, Scanora 3D (S3D) and NewTom VGi (NTV) and a spiral CT (SCT) scanner (Somatom Emotion 16 multislice spiral CT);. Subsequently, the HU and GSV values were determined and evaluated. The data were analyzed by the Kruskal-Wallis and Mann-Whitney U tests. The level of significance was determined at 0.05. Results: There were significant differences among the three different scanners (P<0.05). The differences between HU/GSV values of 12 selected dental materials using NTV was significant (P<0.05) and for S3D and SCT was insignificant (P>0.05). All tested materials showed maximum values in S3D and SCT (3094 and 3071, respectively); however, bone and dentin showed low/medium values (P<0.05). In contrast, the tested materials and tissues showed a range of values in NTV (366 to15383; P<0.05). Conclusion: Scanner system can influence the obtained HU/GSV of dental materials. NTV can discriminate various dental materials, in contrast to S3D/SCT scanners. NTV may be a more useful diagnostic aid for clinical practice. PMID:25386210

  4. Determination of CT number and density profile of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using computed tomography imaging and electron density phantom

    SciTech Connect

    Yusof, Mohd Fahmi Mohd Hamid, Puteri Nor Khatijah Abdul; Tajuddin, Abdul Aziz; Bauk, Sabar; Hashim, Rokiah

    2015-04-29

    Plug density phantoms were constructed in accordance to CT density phantom model 062M CIRS using binderless, pre-treated and tannin-based Rhizophora Spp. particleboards. The Rhizophora Spp. plug phantoms were scanned along with the CT density phantom using Siemens Somatom Definition AS CT scanner at three CT energies of 80, 120 and 140 kVp. 15 slices of images with 1.0 mm thickness each were taken from the central axis of CT density phantom for CT number and CT density profile analysis. The values were compared to water substitute plug phantom from the CT density phantom. The tannin-based Rhizophora Spp. gave the nearest value of CT number to water substitute at 80 and 120 kVp CT energies with χ{sup 2} value of 0.011 and 0.014 respectively while the binderless Rhizphora Spp. gave the nearest CT number to water substitute at 140 kVp CT energy with χ{sup 2} value of 0.023. The tannin-based Rhizophora Spp. gave the nearest CT density profile to water substitute at all CT energies. This study indicated the suitability of Rhizophora Spp. particleboard as phantom material for the use in CT imaging studies.

  5. Determination of CT number and density profile of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using computed tomography imaging and electron density phantom

    NASA Astrophysics Data System (ADS)

    Yusof, Mohd Fahmi Mohd; Hamid, Puteri Nor Khatijah Abdul; Bauk, Sabar; Hashim, Rokiah; Tajuddin, Abdul Aziz

    2015-04-01

    Plug density phantoms were constructed in accordance to CT density phantom model 062M CIRS using binderless, pre-treated and tannin-based Rhizophora Spp. particleboards. The Rhizophora Spp. plug phantoms were scanned along with the CT density phantom using Siemens Somatom Definition AS CT scanner at three CT energies of 80, 120 and 140 kVp. 15 slices of images with 1.0 mm thickness each were taken from the central axis of CT density phantom for CT number and CT density profile analysis. The values were compared to water substitute plug phantom from the CT density phantom. The tannin-based Rhizophora Spp. gave the nearest value of CT number to water substitute at 80 and 120 kVp CT energies with χ2 value of 0.011 and 0.014 respectively while the binderless Rhizphora Spp. gave the nearest CT number to water substitute at 140 kVp CT energy with χ2 value of 0.023. The tannin-based Rhizophora Spp. gave the nearest CT density profile to water substitute at all CT energies. This study indicated the suitability of Rhizophora Spp. particleboard as phantom material for the use in CT imaging studies.

  6. High-resolution CT of temporal bone trauma

    SciTech Connect

    Holland, B.A.; Brant-Zawadzki, M.

    1984-08-01

    Computed tomographic (CT) finding in 18 patients with temporal bone trauma were reviewed. Eight patients suffered longitudinal fractures of the petrous bone, which were associated with ossicular dislocation in two patients. Transverse fractures were detected in six patients, with a contralateral mastoid fracture in one patient. In four patients, the fractures were restricted to the mastoid region. Of the 14 patients in whom adequate neurologic evaluation was available, seven had a permanent facial nerve or hearing deficit while five suffered at least a transient neurologic deficit related to the temporal bone trauma. Routine head CT (10 mm sections) demonstrated only eight of 19 petrous bone injuries. Evidence of brain trauma or extra-axial hemotoma was seen in 12 patients. In 13 cases, high-resolution CT was also performed, demonstrating temporal bone injuries in all. This latter technique allows rapid and detailed evaluation of temporal bone trauma.

  7. Measurements in a High Reynolds Number Wake

    NASA Astrophysics Data System (ADS)

    Hultmark, Marcus; Jimenez, Juan; Bailey, Sean; Smits, Alexander

    2008-11-01

    Experiments were conducted in the Princeton/ONR HRTF windtunnel with highly pressurized air. The wake of a DARPA SUBOFF submarine model was measured over a large range of Reynolds numbers at 5 different downstream locations. The model is an axisymmetric body without appendages (fins) supported by a streamlined support, mimicking a semi-infinite sail. For all Reynolds numbers studied, the mean velocity distribution becomes self-similar between 3 and 6 diameters, D, downstream for the side where the support is not located. In contrast, self-similarity in the Reynolds stresses is not reached at the furthest downstream location (x/D=15). The spectra reveal two peaks in the near-wake. The lower wavenumber peak corresponds to a Strouhal number based on diameter and freestream velocity of about 0.22, suggesting that it is associated with an azimuthal or helical shedding mode in the wake. This mode is evident at all Reynolds numbers, at all cross-stream positions, indicating that it is unlikely to be due to the interference of the support wake with the model wake. The mode is seen only for x/D<15, suggesting that it plays a partial role in the approach to self-similarity of the turbulent stresses.

  8. Quark number fluctuations at high temperatures

    SciTech Connect

    Petreczky, P.; Hegde, P.; Velytsky, A.

    2009-11-01

    We calculate the second, fourth and sixth order quark number fluctuations in the deconfined phase of 2+1 flavor QCD using lattices with temporal extent N{sub t} = 4,6,8 and 12. We consider light, strange and charm quarks. We use p4 action for valence quarks and gauge configurations generated with p4 action with physical value of the strange quark mass and light quark mass m{sub q} = 0.1 m{sub s} generated by the RBC-Bielefeld collaboration. We observe that for all quark masses the quark number fluctuations rapidly get close to the corresponding ideal gas limits. We compare our results to predictions of a quasi-particle model and resummed high temperature perturbative calculations. We also investigate correlations among different flavor channels.

  9. Conversion of the energy-subtracted CT number to electron density based on a single linear relationship: an experimental verification using a clinical dual-source CT scanner.

    PubMed

    Tsukihara, Masayoshi; Noto, Yoshiyuki; Hayakawa, Takahide; Saito, Masatoshi

    2013-05-01

    In radiotherapy treatment planning, the conversion of the computed tomography (CT) number to electron density is one of the main processes that determine the accuracy of patient dose calculations. However, in general, the CT number and electron density of tissues cannot be interrelated using a simple one-to-one correspondence. This study aims to experimentally verify the clinical feasibility of an existing novel conversion method proposed by the author of this note, which converts the energy-subtracted CT number (ΔHU) to the relative electron density (ρe) via a single linear relationship by using a dual-energy CT (DECT). The ΔHU-ρe conversion was performed using a clinical second-generation dual-source CT scanner operated in the dual-energy mode with tube potentials of 80 kV and 140 kV with and without an additional tin filter. The ΔHU-ρe calibration line was obtained from the DECT image acquisition for tissue substitutes in an electron density phantom. In addition, the effect of object size on ΔHU-ρe conversion was also experimentally investigated. The plot of the measured ΔHU versus nominal ρe values exhibited a single linear relationship over a wide ρe range from 0.00 (air) to 2.35 (aluminum). The ΔHU-ρe conversion performed with the tin filter yielded a lower dose and more reliable ρe values that were less affected by the object-size variation when compared to the corresponding values obtained for the case without the tin filter. PMID:23571116

  10. Conversion of the energy-subtracted CT number to electron density based on a single linear relationship: an experimental verification using a clinical dual-source CT scanner

    NASA Astrophysics Data System (ADS)

    Tsukihara, Masayoshi; Noto, Yoshiyuki; Hayakawa, Takahide; Saito, Masatoshi

    2013-05-01

    In radiotherapy treatment planning, the conversion of the computed tomography (CT) number to electron density is one of the main processes that determine the accuracy of patient dose calculations. However, in general, the CT number and electron density of tissues cannot be interrelated using a simple one-to-one correspondence. This study aims to experimentally verify the clinical feasibility of an existing novel conversion method proposed by the author of this note, which converts the energy-subtracted CT number (ΔHU) to the relative electron density (ρe) via a single linear relationship by using a dual-energy CT (DECT). The ΔHU-ρe conversion was performed using a clinical second-generation dual-source CT scanner operated in the dual-energy mode with tube potentials of 80 kV and 140 kV with and without an additional tin filter. The ΔHU-ρe calibration line was obtained from the DECT image acquisition for tissue substitutes in an electron density phantom. In addition, the effect of object size on ΔHU-ρe conversion was also experimentally investigated. The plot of the measured ΔHU versus nominal ρe values exhibited a single linear relationship over a wide ρe range from 0.00 (air) to 2.35 (aluminum). The ΔHU-ρe conversion performed with the tin filter yielded a lower dose and more reliable ρe values that were less affected by the object-size variation when compared to the corresponding values obtained for the case without the tin filter.

  11. Turbulent convection at high Rayleigh numbers

    NASA Astrophysics Data System (ADS)

    Ahlers, Guenter

    2015-11-01

    Russ Donnelly had a vision of building a ten-meter tall Rayleigh-Bénard convection cell for use at helium temperatures at one of the high-energy physics facilities with very large helium liquefaction capacity. It would have reached Rayleigh numbers in the 1020 range and had the promise of yielding detailed information about the so-called ultimate state of turbulent convection which is highly relevant to many geophysical and astrophysical problems as well as to oceanography and climate physics. Although this was not to happen for reasons beyond his control, a laboratory-sized precursor of this venture yielded data for Ra up to 1017. The results were interpreted to yield no definitive indication of a transition to the ultimate state. This talk will review some of these data and compare them with more recent measurements using SF6 at ambient temperatures and high pressure. This comparison suggests that the Donnelly group actually entered a transition range to the ultimate state near Ra1* ~= 6 ×1012 , but re-entered the classical state at larger Ra because with increasing Ra the Prandtl number (which affects Ra1*) also increased in those experiments. In view of the above, one can estimate that, for the same parameter values, the originally envisioned ten-meter cell could have yielded a range of a couple of decades of Ra in the ultimate state. Supported by NSF Grant DMR11-58514.

  12. Preston Probe Calibrations at High Reynolds Number

    NASA Technical Reports Server (NTRS)

    Smits, Alexander J.

    1998-01-01

    The overall goal of the research effort is to study the performance of two Preston probes designed by NASA Langley Research Center across an unprecedented range of Reynolds number (based on friction velocity and probe diameter), and perform an accurate calibration over the same Reynolds number range. Using the Superpipe facility in Princeton, two rounds of experiments were performed. In each round of experiments for each Reynolds number, the pressure gradient, static pressure from the Preston probes and the total pressure from the Preston probes were measured. In the first round, 3 Preston probes having outer diameters of 0.058 inches, 0.083 inches and 0.203 inches were tested over a large range of pipe Reynolds numbers. Two data reduction methods were employed: first, the static pressure measured on the Preston probe was used to calculate P (modified Preston probe configuration), and secondly, the static pressure measured at the reference pressure tap was used to calculate P (un-modified Preston probe configuration). For both methods, the static pressure was adjusted to correspond with the static pressure at the Preston probe tip using the pressure gradient. The measurements for Preston probes with diameters of 0.058 inches, and 0.083 inches respectively were performed in the test pipe before it was polished a second time. Therefore, the measurements at high pipe Reynolds numbers may have been affected by roughness. In the second round of experiments the 0.058 inches and 0.083 inches diameter, un-modified probes were tested after the pipe was polished and prepared to ensure that the surface was smooth. The average velocity was estimated by assuming that the connection between the centerline velocity and the average velocity was known, and by using a Pitot tube to measure the centerline velocity. A preliminary error estimate suggests that it is possible to introduce a 1% to 2% error in estimating the average velocity using this approach. The evidence on the errors

  13. Application of offset-CT scanning to the inspection of high power feeder lines and connections

    NASA Astrophysics Data System (ADS)

    Schneberk, Daniel; Maziuk, Robert; Soyfer, Boris; Shashishekhar, N.; Alreja, Rahul

    2016-02-01

    VJT is developing techniques and scanning methods for the in-situ Radiographic and Computed Tomographic inspection of underground high-power feeder cables. The goals for the inspection are to measure the 3D state of the cables and the cable-connections. Recent in-situ Digital Radiographic inspections performed by VJT have demonstrated the value of NDE inspection information for buried power lines. These NDE data have raised further questions as to the exact state of the cables and connections and pointed to the need for more 3D information of the type provided by volumetric CT scanning. VJT is pursuing a three phased approach to address the many issues involved in this type of inspection: 1) develop a high-power feeder-cable test-bed CT scanner, 2) acquire scans on underground feeder pipes that have been removed from service, and 3) from the work in 1) and 2) develop limited-angle CT scanning methods for extending in-situ Digital Radiography to volumetric CT measurements. To this end, VJT has developed and fielded a high-energy test-bed Gantry-type CT scanner (the source and detector move around the object) with a number of important properties. First, the geometry of the gantry-scans can be configured to match the techniques used in the in-situ radiographic inspection. The same X-ray source is employed as in portable Radiographic inspections, a 7.5 MeV Betatron coupled to a Perkin-Elmer Amorphous Silicon detector. Offset-CT scanning is employed as the high-power feeder line assembly is larger than the detector. A description of this scanner and the scan geometry will be presented showing the connection to in-situ radiography. Results from the CT scans of high-power feeder-cable specimens removed from service will be presented with a focus on the inspection potential of volumetric CT data on these assemblies. An evaluation of the scan performance properties of these data compared to the spectrum of life-cycle inspection issues will be presented. Continuing and

  14. Binary droplet collision at high Weber number

    NASA Astrophysics Data System (ADS)

    Pan, Kuo-Long; Chou, Ping-Chung; Tseng, Yu-Jen

    2009-09-01

    By using the techniques developed for generating high-speed droplets, we have systematically investigated binary droplet collision when the Weber number (We) was increased from the range usually tested in previous studies on the order of 10 to a much larger value of about 5100 for water (a droplet at 23 m/s with a diameter of 0.7 mm). Various liquids were also used to explore the effects of viscosity and surface tension. Specifically, beyond the well-known regimes at moderate We’s, which exhibited coalescence, separation, and separation followed by satellite droplets, we found different behaviors showing a fingering lamella, separation after fingering, breakup of outer fingers, and prompt splattering into multiple secondary droplets as We was increased. The critical Weber numbers that mark the boundaries between these impact regimes are identified. The specific impact behaviors, such as fingering and prompt splattering or splashing, share essential similarity with those also observed in droplet-surface impacts, whereas substantial variations in the transition boundaries may result from the disparity of the boundary conditions at impacts. To compare the outcomes of both types of collisions, a simple model based on energy conservation was carried out to predict the maximum diameter of an expanding liquid disk for a binary droplet collision. The results oppose the dominance of viscous drag, as proposed by previous studies, as the main deceleration force to effect a Rayleigh-Taylor instability and ensuing periphery fingers, which may further lead to the formations of satellite droplets.

  15. Ring artifact correction for high-resolution micro CT.

    PubMed

    Kyriakou, Yiannis; Prell, Daniel; Kalender, Willi A

    2009-09-01

    In high-resolution micro CT using flat detectors (FD), imperfect or defect detector elements may cause concentric-ring artifacts due to their continuous over- or underestimation of attenuation values, which often disturb image quality. We here present a dedicated image-based ring artifact correction method for high-resolution micro CT, based on median filtering of the reconstructed image and working on a transformed version of the reconstructed images in polar coordinates. This post-processing method reduced ring artifacts in the reconstructed images and improved image quality for phantom and in in vivo scans. Noise and artifacts were reduced both in transversal and in multi-planar reformations along the longitudinal axis. PMID:19661571

  16. An improved method for the removal of ring artifacts in high resolution CT imaging

    NASA Astrophysics Data System (ADS)

    Rashid, Sabrina; Lee, Soo Yeol; Hasan, Md Kamrul

    2012-12-01

    In high resolution computed tomography (CT) using flat panel detectors, imperfect or defected detector elements cause stripe artifacts in sinogram which results in concentric ring artifacts in the image. Such ring artifacts obscure image details in the regions of interest of the image. In this article, novel techniques are proposed for the detection, classification, and correction of ring artifacts in the sinogram domain. The proposed method is suitable for multislice CT with parallel or fan beam geometry. It can also be employed for ring artifact removal in 3D cone beam volume CT by adopting a sinogram by sinogram processing technique. The detection algorithm is based on applying data driven thresholds on the mean curve and difference curve of the sinogram. The ring artifacts are classified into three types and a separate correction algorithm is used for each class. The performance of the proposed techniques is evaluated on a number of real micro-CT images. Experimental results corroborate that the proposed algorithm can remove ring artifacts from micro-CT images more effectively as compared to other recently reported techniques in the literature.

  17. SU-E-J-268: Change of CT Number During the Course of Chemoradiation Therapy for Pancreatic Cancer

    SciTech Connect

    Chen, X; Dalah, E; Liu, F; Li, X; Zhang, J

    2015-06-15

    Purpose: It has been observed radiation can induce changes in CT number (CTN) inside tumor during the course of radiation therapy (RT) for several tumor sites including lung and head and neck, suggesting that the CTN change may be potentially used to assess RT response. In this study, we investigate the CTN changes inside tumor during the course of chemoradiation therapy (CRT) for pancreatic cancer. Methods: Daily diagnostic-quality CT data acquired during IGRT for 17 pancreatic head cancer patients using an in-room CT (CTVision, Siemens) were analyzed. All patients were treated with a radiation dose of 50.4 in 1.8 Gy per fraction. On each daily CT set, The contour of the pancreatic head, included in the treatment target, was generated by populating the pancreatic head contour from the planning CT or MRI using an auto-segmentation tool based on deformable registration (ABAS, Elekta) with manual editing if necessary. The CTN at each voxel in the pancreatic head contour was extracted and the 3D distribution of the CTNs was processed using MATLAB. The mean value of CTN distribution was used to quantify the daily CTN change in the pancreatic head. Results: Reduction of CTN in pancreatic head was observed during the CRT delivery in 14 out the 17 (82%) patients studied. Although the average reduction is only 3.5 Houncefield Unit (HU), this change is significant (p<0.01). Among them, there are 7 patients who had a CTN drop larger than 5 HU, ranging from 6.0 to 11.8 HU. In contrast to this trend, CTN was increased in 3 patients. Conclusion: Measurable changes in the CT number in tumor target were observed during the course of chemoradiation therapy for the pancreas cancer patients, indicating this radiation-induced CTN change may be used to assess treatment response.

  18. High speed optical quantum random number generation.

    PubMed

    Fürst, Martin; Weier, Henning; Nauerth, Sebastian; Marangon, Davide G; Kurtsiefer, Christian; Weinfurter, Harald

    2010-06-01

    We present a fully integrated, ready-for-use quantum random number generator (QRNG) whose stochastic model is based on the randomness of detecting single photons in attenuated light. We show that often annoying deadtime effects associated with photomultiplier tubes (PMT) can be utilized to avoid postprocessing for bias or correlations. The random numbers directly delivered to a PC, generated at a rate of up to 50 Mbit/s, clearly pass all tests relevant for (physical) random number generators. PMID:20588431

  19. Noise, sampling, and the number of projections in cone-beam CT with a flat-panel detector

    PubMed Central

    Zhao, Z.; Gang, G. J.; Siewerdsen, J. H.

    2014-01-01

    Purpose: To investigate the effect of the number of projection views on image noise in cone-beam CT (CBCT) with a flat-panel detector. Methods: This fairly fundamental consideration in CBCT system design and operation was addressed experimentally (using a phantom presenting a uniform medium as well as statistically motivated “clutter”) and theoretically (using a cascaded systems model describing CBCT noise) to elucidate the contributing factors of quantum noise (σQ), electronic noise (σE), and view aliasing (σview). Analysis included investigation of the noise, noise-power spectrum, and modulation transfer function as a function of the number of projections (Nproj), dose (Dtot), and voxel size (bvox). Results: The results reveal a nonmonotonic relationship between image noise and Nproj at fixed total dose: for the CBCT system considered, noise decreased with increasing Nproj due to reduction of view sampling effects in the regime Nproj <∼200, above which noise increased with Nproj due to increased electronic noise. View sampling effects were shown to depend on the heterogeneity of the object in a direct analytical relationship to power-law anatomical clutter of the form κ/f β—and a general model of individual noise components (σQ, σE, and σview) demonstrated agreement with measurements over a broad range in Nproj, Dtot, and bvox. Conclusions: The work elucidates fairly basic elements of CBCT noise in a manner that demonstrates the role of distinct noise components (viz., quantum, electronic, and view sampling noise). For configurations fairly typical of CBCT with a flat-panel detector (FPD), the analysis reveals a “sweet spot” (i.e., minimum noise) in the range Nproj ∼ 250–350, nearly an order of magnitude lower in Nproj than typical of multidetector CT, owing to the relatively high electronic noise in FPDs. The analysis explicitly relates view aliasing and quantum noise in a manner that includes aspects of the object (“clutter”) and

  20. Noise, sampling, and the number of projections in cone-beam CT with a flat-panel detector

    SciTech Connect

    Zhao, Z.; Gang, G. J.; Siewerdsen, J. H.

    2014-06-15

    Purpose: To investigate the effect of the number of projection views on image noise in cone-beam CT (CBCT) with a flat-panel detector. Methods: This fairly fundamental consideration in CBCT system design and operation was addressed experimentally (using a phantom presenting a uniform medium as well as statistically motivated “clutter”) and theoretically (using a cascaded systems model describing CBCT noise) to elucidate the contributing factors of quantum noise (σ{sub Q}), electronic noise (σ{sub E}), and view aliasing (σ{sub view}). Analysis included investigation of the noise, noise-power spectrum, and modulation transfer function as a function of the number of projections (N{sub proj}), dose (D{sub tot}), and voxel size (b{sub vox}). Results: The results reveal a nonmonotonic relationship between image noise andN{sub proj} at fixed total dose: for the CBCT system considered, noise decreased with increasing N{sub proj} due to reduction of view sampling effects in the regime N{sub proj} <∼200, above which noise increased with N{sub proj} due to increased electronic noise. View sampling effects were shown to depend on the heterogeneity of the object in a direct analytical relationship to power-law anatomical clutter of the form κ/f {sup β}—and a general model of individual noise components (σ{sub Q}, σ{sub E}, and σ{sub view}) demonstrated agreement with measurements over a broad range in N{sub proj}, D{sub tot}, and b{sub vox}. Conclusions: The work elucidates fairly basic elements of CBCT noise in a manner that demonstrates the role of distinct noise components (viz., quantum, electronic, and view sampling noise). For configurations fairly typical of CBCT with a flat-panel detector (FPD), the analysis reveals a “sweet spot” (i.e., minimum noise) in the rangeN{sub proj} ∼ 250–350, nearly an order of magnitude lower in N{sub proj} than typical of multidetector CT, owing to the relatively high electronic noise in FPDs. The analysis

  1. An experimental study of high Rayleigh number and high Prandtl number Bénard convection

    NASA Astrophysics Data System (ADS)

    Weeraratne, Dayanthie; Manga, Michael

    1998-11-01

    We performed a set of 25 experiments using corn syrup with a temperature-dependent viscosity for Rayleigh numbers 10^4 < Ra < 10^8 and Prandtl numbers 10^3 < Pr < 10^6; viscosity is based on the average temperature at the top and bottom of the layer. As Ra increases, we observe a transition from steady to time-dependent flow at Ra=O(10^5). A second transition occurs at Ra=O(10^6) where large scale flow is gradually replaced by isolated rising and sinking plumes. Plumes have mushroom-shaped heads and continuous tails attached to their respective thermal boundary layers and decrease in radius with increasing Ra. Previous studies for Ra < O(10^5) find that the Nusselt number Nu = 0.197Ra^0.276. At Ra greater than O(10^7) we find that the Nu is below this trend. The Reynolds number Re = Ra^1/2/Pr ranges from O(10-1) to O(10^1) for these high Ra experiments; we attribute the reduced Nu to inertial effects which reduce both plume size and velocity.

  2. Stapes model using high-resolution μCT

    NASA Astrophysics Data System (ADS)

    Baek, Jong Dae; Puria, Sunil

    2008-02-01

    Understanding the biomechanics of the middle ear is important for surgical reconstructions. As the output of the middle ear, the stapes plays a key role in transferring acoustic vibrations to the cochlea. In order to develop anatomically-based mathematical models, which are needed to improve our understanding of stapes dynamics, detailed morphometry of the stapes is required. High-resolution micro-CT imaging techniques were used to generate three-dimensional reconstructions of cadaveric temporal bones from 5 species commonly used in experimental middle ear research: the chinchilla, human (relatively mid-frequency hearing limit), cat, guinea pig, and gerbil (relatively high-frequency hearing limit). From the standard discretizations of micro-CT images and corresponding 3-D volume reconstructions, the centers of mass, principle axes, stapes head areas and stapes footplate areas were calculated. Mechanical relationships were estimated between the capitulum area and the footplate area and inter-species comparisons were performed between the cross-sectional shapes of the anterior and posterior crura. Quantitative dynamic properties were estimated from the rigid body motion calculations. The parameters estimated in this study will be useful for building biocomputational models of the stapes for a variety of species.

  3. A new method to measure electron density and effective atomic number using dual-energy CT images.

    PubMed

    Garcia, Luis Isaac Ramos; Azorin, José Fernando Pérez; Almansa, Julio F

    2016-01-01

    The purpose of this work is to present a new method to extract the electron density ([Formula: see text]) and the effective atomic number (Z eff) from dual-energy CT images, based on a Karhunen-Loeve expansion (KLE) of the atomic cross section per electron. This method was used to calibrate a Siemens Definition CT using the CIRS phantom. The predicted electron density and effective atomic number using 80 kVp and 140 kVp were compared with a calibration phantom and an independent set of samples. The mean absolute deviations between the theoretical and calculated values for all the samples were 1.7 %  ±  0.1 % for [Formula: see text] and 4.1 %  ±  0.3 % for Z eff. Finally, these results were compared with other stoichiometric method. The application of the KLE to represent the atomic cross section per electron is a promising method for calculating [Formula: see text] and Z eff using dual-energy CT images. PMID:26649484

  4. A new method to measure electron density and effective atomic number using dual-energy CT images

    NASA Astrophysics Data System (ADS)

    Ramos Garcia, Luis Isaac; Pérez Azorin, José Fernando; Almansa, Julio F.

    2016-01-01

    The purpose of this work is to present a new method to extract the electron density ({ρ\\text{e}} ) and the effective atomic number (Z eff) from dual-energy CT images, based on a Karhunen-Loeve expansion (KLE) of the atomic cross section per electron. This method was used to calibrate a Siemens Definition CT using the CIRS phantom. The predicted electron density and effective atomic number using 80 kVp and 140 kVp were compared with a calibration phantom and an independent set of samples. The mean absolute deviations between the theoretical and calculated values for all the samples were 1.7 %  ±  0.1 % for {ρ\\text{e}} and 4.1 %  ±  0.3 % for Z eff. Finally, these results were compared with other stoichiometric method. The application of the KLE to represent the atomic cross section per electron is a promising method for calculating {ρ\\text{e}} and Z eff using dual-energy CT images.

  5. The High/Scope Report. Number Four.

    ERIC Educational Resources Information Center

    Silverman, Charles, Ed.

    This report provides articles on several topics related to the education of young children. In the introduction High/Scope President David P. Weikart suggests that public investment in preschool education is a wise and economically sound social policy. New studies of the long term effects of preschool are demonstrating the staying power of early…

  6. Assessment of CT numbers in limited and medium field-of-view scans taken using Accuitomo 170 and Veraviewepocs 3De cone-beam computed tomography scanners

    PubMed Central

    Oliveira, Matheus L.; Tosoni, Guilherme M.; Lindsey, David H.; Mendoza, Kristopher; Tetradis, Sotirios

    2014-01-01

    Purpose To assess the influence of anatomic location on the relationship between computed tomography (CT) number and X-ray attenuation in limited and medium field-of-view (FOV) scans. Materials and Methods Tubes containing solutions with different concentrations of K2HPO4 were placed in the tooth sockets of a human head phantom. Cone-beam computed tomography (CBCT) scans were acquired, and CT numbers of the K2HPO4 solutions were measured. The relationship between CT number and K2HPO4 concentration was examined by linear regression analyses. Then, the variation in CT number according to anatomic location was examined. Results The relationship between K2HPO4 concentration and CT number was strongly linear. The slopes of the linear regressions for the limited FOVs were almost 2-fold lower than those for the medium FOVs. The absolute CT number differed between imaging protocols and anatomic locations. Conclusion There is a strong linear relationship between X-ray attenuation and CT number. The specific imaging protocol and anatomic location of the object strongly influence this relationship. PMID:25473635

  7. High-Pitch CT Pulmonary Angiography in Third Generation Dual-Source CT: Image Quality in an Unselected Patient Population

    PubMed Central

    Sabel, Bastian O.; Buric, Kristijan; Karara, Nora; Thierfelder, Kolja M.; Dinkel, Julien; Sommer, Wieland H.; Meinel, Felix G.

    2016-01-01

    Objectives To investigate the feasibility of high-pitch CT pulmonary angiography (CTPA) in 3rd generation dual-source CT (DSCT) in unselected patients. Methods Forty-seven patients with suspected pulmonary embolism underwent high-pitch CTPA on a 3rd generation dual-source CT scanner. CT dose index (CTDIvol) and dose length product (DLP) were obtained. Objective image quality was analyzed by calculating signal-to-noise-ratio (SNR) and contrast-to-noise ratio (CNR). Subjective image quality on the central, lobar, segmental and subsegmental level was rated by two experienced radiologists. Results Median CTDI was 8.1 mGy and median DLP was 274 mGy*cm. Median SNR was 32.9 in the central and 31.9 in the segmental pulmonary arteries. CNR was 29.2 in the central and 28.2 in the segmental pulmonary arteries. Median image quality was “excellent” in central and lobar arteries and “good” in subsegmental arteries according to both readers. Segmental arteries varied between “excellent” and “good”. Image quality was non-diagnostic in one case (2%), beginning in the lobar arteries. Thirteen patients (28%) showed minor motion artifacts. Conclusions In third-generation dual-source CT, high-pitch CTPA is feasible for unselected patients. It yields excellent image quality with minimal motion artifacts. However, compared to standard-pitch cohorts, no distinct decrease in radiation dose was observed. PMID:26872262

  8. Impact of number of repeated scans on model observer performance for a low-contrast detection task in CT

    NASA Astrophysics Data System (ADS)

    Ma, Chi; Yu, Lifeng; Chen, Baiyu; Vrieze, Thomas; Favazza, Christopher; Leng, Shuai; McCollough, Cynthia

    2015-03-01

    In previous investigations on CT image quality, channelized Hotelling observer (CHO) models have been shown to well represent human observer performance in several phantom-based detection/discrimination tasks. In these studies, a large number of independent images was necessary to estimate the expectation images and covariance matrices for each test condition. The purpose of this study is to investigate how the number of repeated scans affects the precision and accuracy of the CHO's performance in a signal-known-exactly detection task. A phantom containing 21 low-contrast objects (3 contrast levels and 7 sizes) was scanned with a 128-slice CT scanner at three dose levels. For each dose level, 100 independent images were acquired for each test condition. All images were reconstructed using filtered-backprojection (FBP) and a commercial iterative reconstruction algorithm. For each combination of dose level and reconstruction method, the low-contrast detectability, quantified with the area under receiver operating characteristic curve (Az), was calculated using a previously validated CHO model. To determine the dependency of CHO performance on the number of repeated scans, the Az value was calculated for different number of channel filters, for each object size and contrast, and for different dose/reconstruction settings using all 100 repeated scans. The Az values were also calculated using randomly selected subsets of the scans (from 10 to 90 scans with an increment of 10 scans). Using the Az from the 100 scans as the reference, the accuracy of Az values calculated from a fewer number of scans was determined and the minimal number of scans was subsequently derived. For the studied signal-known-exactly detection task, results demonstrated that, the minimal number of scans depends on dose level, object size and contrast level, and channel filters.

  9. A comprehensive study on decreasing the kilovoltage cone-beam CT dose by reducing the projection number.

    PubMed

    Lu, Bo; Lu, Haibin; Palta, Jatinder

    2010-01-01

    The objective of this study was to evaluate the effect of kilovoltage cone-beam computed tomography (CBCT) on registration accuracy and image qualities with a reduced number of planar projections used in volumetric imaging reconstruction. The ultimate goal is to evaluate the possibility of reducing the patient dose while maintaining registration accuracy under different projection-number schemes for various clinical sites. An Elekta Synergy Linear accelerator with an onboard CBCT system was used in this study. The quality of the Elekta XVI cone-beam three-dimensional volumetric images reconstructed with a decreasing number of projections was quantitatively evaluated by a Catphan phantom. Subsequently, we tested the registration accuracy of imaging data sets on three rigid anthropomorphic phantoms and three real patient sites under the reduced projection-number (as low as 1/6th) reconstruction of CBCT data with different rectilinear shifts and rota-tions. CBCT scan results of the Catphan phantom indicated the CBCT images got noisier when the number of projections was reduced, but their spatial resolution and uniformity were hardly affected. The maximum registration errors under the small amount transformation of the reference CT images were found to be within 0.7 mm translation and 0.3 masculine rotation. However, when the projection number was lower than one-fourth of the full set with a large amount of transformation of reference CT images, the registration could easily be trapped into local minima solutions for a nonrigid anatomy. We concluded, by using projection-number reduction strategy under conscientious care, imaging-guided localization procedure could achieve a lower patient dose without losing the registration accuracy for various clinical sites and situations. A faster scanning time is the main advantage compared to the mA decrease-based, dose-reduction method. PMID:20717096

  10. High resolution X-ray micro-CT of ultra-thin wall space components

    NASA Astrophysics Data System (ADS)

    Roth, D. J.; Rauser, R. W.; Bowman, R. R.; Bonacuse, P. J.; Martin, R. E.; Locci, I. E.; Kelley, M.

    2013-01-01

    A high resolution micro-CT system has been assembled and is being used to provide optimal characterization for ultra-thin wall space components. The Glenn Research Center NDE Sciences Team, using this CT system, has assumed the role of inspection vendor for the Advanced Stirling Convertor (ASC) project at NASA. This article will discuss many aspects of the development of the CT scanning for this type of component, including CT system overview; inspection requirements; process development, software utilized and developed to visualize, process, and analyze results; calibration sample development; results on actual samples; correlation with optical/SEM characterization; CT modeling; and development of automatic flaw recognition software.

  11. High-resolution and high-speed CT in industry and research

    NASA Astrophysics Data System (ADS)

    Zabler, S.; Fella, C.; Dietrich, A.; Nachtrab, F.; Salamon, Michael; Voland, V.; Ebensperger, T.; Oeckl, S.; Hanke, R.; Uhlmann, N.

    2012-10-01

    The application of industrial CT covers many orders of magnitude of object sizes, ranging from freight containers (few meters) down to liquid foams (i.e. for food industry) or even parts of insects which are only several hundreds of micrometers in size. Similarly, the specifications for acquisition speed extend over some orders of magnitude, from hours to sub-second CT. We present the current technology in terms of X-ray sources and detectors, along with numerous applications from industry and materials research: e.g. industrial high-speed CT of car pistons, in situ micro-CT of milk foam decay at micrometer spatial resolution and 8 s scan time, as well as ex situ scans of tensile tested Nickel-alloys. The Fraunhofer Development Center X-ray Technology (Fürth, Germany) and the Chair of X-ray Microscopy (University Würzburg, Germany) are currently working on extending the technological limits, demonstrated, e,g. by the development of advanced X-ray detectors or a new inhouse CT system which comprises a high-brilliance liquid metal jet anode.

  12. Initial implementation of the conversion from the energy-subtracted CT number to electron density in tissue inhomogeneity corrections: An anthropomorphic phantom study of radiotherapy treatment planning

    SciTech Connect

    Tsukihara, Masayoshi; Noto, Yoshiyuki; Sasamoto, Ryuta; Hayakawa, Takahide; Saito, Masatoshi

    2015-03-15

    Purpose: To achieve accurate tissue inhomogeneity corrections in radiotherapy treatment planning, the authors had previously proposed a novel conversion of the energy-subtracted computed tomography (CT) number to an electron density (ΔHU–ρ{sub e} conversion), which provides a single linear relationship between ΔHU and ρ{sub e} over a wide range of ρ{sub e}. The purpose of this study is to present an initial implementation of the ΔHU–ρ{sub e} conversion method for a treatment planning system (TPS). In this paper, two example radiotherapy plans are used to evaluate the reliability of dose calculations in the ΔHU–ρ{sub e} conversion method. Methods: CT images were acquired using a clinical dual-source CT (DSCT) scanner operated in the dual-energy mode with two tube potential pairs and an additional tin (Sn) filter for the high-kV tube (80–140 kV/Sn and 100–140 kV/Sn). Single-energy CT using the same DSCT scanner was also performed at 120 kV to compare the ΔHU–ρ{sub e} conversion method with a conventional conversion from a CT number to ρ{sub e} (Hounsfield units, HU–ρ{sub e} conversion). Lookup tables for ρ{sub e} calibration were obtained from the CT image acquisitions for tissue substitutes in an electron density phantom (EDP). To investigate the beam-hardening effect on dosimetric uncertainties, two EDPs with different sizes (a body EDP and a head EDP) were used for the ρ{sub e} calibration. Each acquired lookup table was applied to two radiotherapy plans designed using the XiO TPS with the superposition algorithm for an anthropomorphic phantom. The first radiotherapy plan was for an oral cavity tumor and the second was for a lung tumor. Results: In both treatment plans, the performance of the ΔHU–ρ{sub e} conversion was superior to that of the conventional HU–ρ{sub e} conversion in terms of the reliability of dose calculations. Especially, for the oral tumor plan, which dealt with dentition and bony structures, treatment

  13. High-quality four-dimensional cone-beam CT by deforming prior images

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Gu, Xuejun

    2013-01-01

    Due to a limited number of projections at each phase, severe view aliasing artifacts are present in four-dimensional cone beam computed tomography (4D-CBCT) when reconstruction is performed using conventional algorithms. In this work, we aim to obtain high-quality 4D-CBCT of lung cancer patients in radiation therapy by deforming the planning CT. The deformation vector fields (DVF) to deform the planning CT are estimated through matching the forward projection of the deformed prior image and measured on-treatment CBCT projection. The estimation of the DVF is formulated as an unconstrained optimization problem, where the objective function to be minimized is the sum of the squared difference between the forward projection of the deformed planning CT and the measured 4D-CBCT projection. A nonlinear conjugate gradient method is used to solve the DVF. As the number of the variables in the DVF is much greater than the number of measurements, the solution to such a highly ill-posed problem is very sensitive to the initials during the optimization process. To improve the estimation accuracy of DVF, we proposed a new strategy to obtain better initials for the optimization. In this strategy, 4D-CBCT is first reconstructed by total variation minimization. Demons deformable registration is performed to register the planning CT and the 4D-CBCT reconstructed by total variation minimization. The resulted DVF from demons registration is then used as the initial parameters in the optimization process. A 4D nonuniform rotational B-spline-based cardiac-torso (NCAT) phantom and a patient 4D-CBCT are used to evaluate the algorithm. Image quality of 4D-CBCT is substantially improved by using the proposed strategy in both NCAT phantom and patient studies. The proposed method has the potential to improve the temporal resolution of 4D-CBCT. Improved 4D-CBCT can better characterize the motion of lung tumors and will be a valuable tool for image-guided adaptive radiation therapy.

  14. Reduction of ring artefacts in high resolution micro-CT reconstructions.

    PubMed

    Sijbers, Jan; Postnov, Andrei

    2004-07-21

    High resolution micro-CT images are often corrupted by ring artefacts, prohibiting quantitative analysis and hampering post processing. Removing or at least significantly reducing such artefacts is indispensable. However, since micro-CT systems are pushed to the extremes in the quest for the ultimate spatial resolution, ring artefacts can hardly be avoided. Moreover, as opposed to clinical CT systems, conventional correction schemes such as flat-field correction do not lead to satisfactory results. Therefore, in this note a simple but efficient and fast post processing method is proposed that effectively reduces ring artefacts in reconstructed micro-CT images. PMID:15357205

  15. NOTE: Reduction of ring artefacts in high resolution micro-CT reconstructions

    NASA Astrophysics Data System (ADS)

    Sijbers, Jan; Postnov, Andrei

    2004-07-01

    High resolution micro-CT images are often corrupted by ring artefacts, prohibiting quantitative analysis and hampering post processing. Removing or at least significantly reducing such artefacts is indispensable. However, since micro-CT systems are pushed to the extremes in the quest for the ultimate spatial resolution, ring artefacts can hardly be avoided. Moreover, as opposed to clinical CT systems, conventional correction schemes such as flat-field correction do not lead to satisfactory results. Therefore, in this note a simple but efficient and fast post processing method is proposed that effectively reduces ring artefacts in reconstructed mgr-CT images.

  16. Evaluation of resolution performance of high energy x-ray CT

    NASA Astrophysics Data System (ADS)

    Abe, Makoto; Fujimoto, Hiroyuki; Sato, Osamu; Sato, Katsutoshi; Takatsuji, Toshiyuki

    2015-07-01

    Dimensional X-ray CT has attracted production industry due to its nature [1] enabling not only external dimensional measurement but also internal dimensional measurement which has been difficult for pre-existing dimensional measurement instruments. However, because the reconstruction process of three dimensional volume image may be affected by various kinds of error sources of the hardware and also the software, performance evaluation of dimensional X-ray CT has become one of the major issues [2], especially for X-ray CT system with higher energy such as several MeV. Resolution performance of high energy X-ray CT was evaluated by using a series of phantoms which equip regular line-and-space structures with various pitch sizes down to 100 micrometer. These phantoms were prototyped in the identical pitch sizes with three different materials. These phantoms were practically measured by a high energy X-ray CT. Results and perspective of the resolution performance is presented.

  17. User Friendly Processing of Sediment CT Data: Software and Application in High Resolution Non-Destructive Sediment Core Data Sets

    NASA Astrophysics Data System (ADS)

    Reilly, B. T.; Stoner, J. S.; Wiest, J.; Abbott, M. B.; Francus, P.; Lapointe, F.

    2015-12-01

    Computed Tomography (CT) of sediment cores allow for high resolution images, three dimensional volumes, and down core profiles, generated through the attenuation of X-rays as a function of density and atomic number. When using a medical CT-Scanner, these quantitative data are stored in pixels using the Hounsfield scale, which are relative to the attenuation of X-rays in water and air at standard temperature and pressure. Here we present MATLAB based software specifically designed for sedimentary applications with a user friendly graphical interface to process DICOM files and stitch overlapping CT scans. For visualization, the software allows easy generation of core slice images with grayscale and false color relative to a user defined Hounsfield number range. For comparison to other high resolution non-destructive methods, down core Hounsfield number profiles are extracted using a method robust to coring imperfections, like deformation, bowing, gaps, and gas expansion. We demonstrate the usefulness of this technique with lacustrine sediment cores from the Western United States and Canadian High Arctic, including Fish Lake, Oregon, and Sawtooth Lake, Ellesmere Island. These sites represent two different depositional environments and provide examples for a variety of common coring defects and lithologies. The Hounsfield profiles and images can be used in combination with other high resolution data sets, including sediment magnetic parameters, XRF core scans and many other types of data, to provide unique insights into how lithology influences paleoenvironmental and paleomagnetic records and their interpretations.

  18. High-density renal cysts in autosomal dominant polycystic kidney disease demonstrated by CT

    SciTech Connect

    Levine, E.; Grantham, J.J.

    1985-02-01

    Unenhanced abdominal CT scans of 35 patients with autosomal dominant polycystic kidney disease (ADPKD) showed multiple high-density (58-84 HU) renal cysts in 42.9% of patients, occasional high-density cysts in 25.7%, and no high-density cysts in 31.4%. These high-density cysts were usually subcapsular and were more frequent in patients with markedly enlarged kidneys and flank pain at the time of CT. Follow-up CT often showed a reduction in cyst densities, although some cysts developed mural calcification and calcification of their contents. Renal carcinomas occur rarely in ADPKD and may occasionally be hyperdense. However, high-density cysts may usually be distinguished from carcinomas on CT by their smooth contours, sharp interfaces with renal parenchyma, homogeneity, and lack of contrast enhancement.

  19. High Resolution X-Ray Micro-CT of Ultra-Thin Wall Space Components

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Rauser, R. W.; Bowman, Randy R.; Bonacuse, Peter; Martin, Richard E.; Locci, I. E.; Kelley, M.

    2012-01-01

    A high resolution micro-CT system has been assembled and is being used to provide optimal characterization for ultra-thin wall space components. The Glenn Research Center NDE Sciences Team, using this CT system, has assumed the role of inspection vendor for the Advanced Stirling Convertor (ASC) project at NASA. This article will discuss many aspects of the development of the CT scanning for this type of component, including CT system overview; inspection requirements; process development, software utilized and developed to visualize, process, and analyze results; calibration sample development; results on actual samples; correlation with optical/SEM characterization; CT modeling; and development of automatic flaw recognition software. Keywords: Nondestructive Evaluation, NDE, Computed Tomography, Imaging, X-ray, Metallic Components, Thin Wall Inspection

  20. Promoting Number Theory in High Schools or Birthday Problem and Number Theory

    ERIC Educational Resources Information Center

    Srinivasan, V. K.

    2010-01-01

    The author introduces the birthday problem in this article. This can amuse willing members of any birthday party. This problem can also be used as the motivational first day lecture in number theory for the gifted students in high schools or in community colleges or in undergraduate classes in colleges.

  1. NOTE: Suppression of high-density artefacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

    NASA Astrophysics Data System (ADS)

    Baissalov, R.; Sandison, G. A.; Donnelly, B. J.; Saliken, J. C.; McKinnon, J. G.; Muldrew, K.; Rewcastle, J. C.

    2000-05-01

    Image guidance in cryotherapy is usually performed using ultrasound. Although not currently in routine clinical use, x-ray CT imaging is an alternative means of guidance that can display the full 3D structure of the iceball, including frozen and unfrozen regions. However, the quality of x-ray CT images is compromised by the presence of high-density streak artefacts. To suppress these artefacts we applied temporal digital subtraction (TDS). This TDS method has the added advantage of improving the grey-scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high-density artefacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced artefact content. Thus TDS can be used to significantly suppress or eliminate high-density CT streak artefacts without reducing the metallic content of the cryoprobes. In vivo study needs to be conducted to establish the utility of this TDS procedure for CT assisted prostate or liver cryotherapy. Applying TDS in x-ray CT guided cryotherapy will facilitate estimation of the number and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

  2. An experimental investigation of turbulent boundary layers at high Mach number and Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Holden, M. S.

    1972-01-01

    Skin friction, heat transfer and pressure measurements were obtained in laminar, transitional and turbulent boundary layers on flat plates at Mach numbers from 7 to 13 at wall-to-free stream stagnation temperature ratios from 0.1 to 0.3. Measurements in laminar flows were in excellent agreement with the theory of Cheng. Correlations of the transition measurements with measurements on flight vehicles and in ballistic ranges show good agreement. Our transition measurements do not correlate well with those of Pate and Schueler. Comparisons have been made between the skin friction and heat transfer measurements and the theories of Van Driest, Eckert and Spalding and Chi. These comparisons reveal in general that at the high end of our Mach number range (10-13) the theory of Van Driest is in best agreement with the data, whereas at lower Mach numbers (6.5-10) the Spalding Chi theory is in better agreement with the measurements.

  3. SU-E-J-190: Characterization of Radiation Induced CT Number Changes in Tumor and Normal Lung During Radiation Therapy for Lung Cancer

    SciTech Connect

    Yang, C; Liu, F; Tai, A; Gore, E; Johnstone, C; Li, X

    2014-06-01

    Purpose: To measure CT number (CTN) changes in tumor and normal lung as a function of radiation therapy (RT) dose during the course of RT delivery for lung cancer using daily IGRT CT images and single respiration phase CT images. Methods: 4D CT acquired during planning simulation and daily 3D CT acquired during daily IGRT for 10 lung cancer cases randomly selected in terms of age, caner type and stage, were analyzed using an in-house developed software tool. All patients were treated in 2 Gy fractions to primary tumors and involved nodal regions. Regions enclosed by a series of isodose surfaces in normal lung were delineated. The obtained contours along with target contours (GTVs) were populated to each singlephase planning CT and daily CT. CTN in term of Hounsfield Unit (HU) of each voxel in these delineated regions were collectively analyzed using histogram, mean, mode and linear correlation. Results: Respiration induced normal lung CTN change, as analyzed from single-phase planning CTs, ranged from 9 to 23 (±2) HU for the patients studied. Normal lung CTN change was as large as 50 (±12) HU over the entire treatment course, was dose and patient dependent and was measurable with dose changes as low as 1.5 Gy. For patients with obvious tumor volume regression, CTN within the GTV drops monotonically as much as 10 (±1) HU during the early fractions with a total dose of 20 Gy delivered. The GTV and CTN reductions are significantly correlated with correlation coefficient >0.95. Conclusion: Significant RT dose induced CTN changes in lung tissue and tumor region can be observed during even the early phase of RT delivery, and may potentially be used for early prediction of radiation response. Single respiration phase CT images have dramatically reduced statistical noise in ROIs, making daily dose response evaluation possible.

  4. SU-E-J-271: Correlation of CT Number Change with Radiation Treatment Response for Pancreatic Cancer

    SciTech Connect

    Dalah, E; Tai, A; Oshima, K; Hall, W; Knechtges, P; Erickson, B; Li, X

    2015-06-15

    Purpose: It has been reported recently that radiation can induce CT number (CTN) change during radiation therapy (RT) delivery. In the effort to explore whether CTN can be used to assess RT response, we analyze the relationship between the pathological treatment response (PTR) and the changes of CTN, MRI, and PET before and after the neoadjuvant chemoradiation (nCR) for pancreatic adenocarcinoma. Methods: The preand post-nCR CT, MRI, and PET data for a total of 8 patients with resectable, or borderline resectable pancreatic head adenocarcinoma treated with nCR were retrospectively analyzed. Radiographic characteristics were correlated to PTR data. The histograms, means and standard derivations (SD) of the CTNs in pancreatic head (CTNPH), the GTV defined by ADC (CTNGTV), and the rest of pancreatic head (CTNPH-CTNGTV) were compared. Changes before and after nCR were correlated with the corresponding changes of ADC, lean body mass normalized SUV (SUVlb), and PTR using Pearson’ s correlation coefficient test. Results: The average mean and SD in CTPH for all the patients analyzed were higher in post-nCR (53.17 ± 31.05 HU) compared to those at pre-nCR (28.09 ± 4.253 HU). The CTNGTV were generally higher than CTNPH and CTNPH-CTNGTV, though the differences were not significant. The post-nCR changes of mean CTN, ADC, and SUVlb values in pancreatic head were correlated with PTR (R=0.3273/P=0.5357, R=−0.5455/P<0.0001, and R=0.7638/P=0.0357, respectively). The mean difference in the maximum tumor dimension measured from CTN, ADC, and SUVlb as compared with pathological measurements was −2.1, −0.5, and 0.22 cm, respectively. Conclusion: The radiation-induced change of CTN in pancreas head after chemoradiation therapy of pancreatic cancer was observed, which may be related to treatment responses as assessed by biological imaging and pathology. More data are needed to determine whether the CTN can be used as a quantitative biomarker for response to neoadjuvant therapy.

  5. Wave phenomena in a high Reynolds number compressible boundary layer

    NASA Technical Reports Server (NTRS)

    Bayliss, A.; Maestrello, L.; Parikh, P.; Turkel, E.

    1985-01-01

    Growth of unstable disturbances in a high Reynolds number compressible boundary layer is numerically simulated. Localized periodic surface heating and cooling as a means of active control of these disturbances is studied. It is shown that compressibility in itself stabilizes the flow but at a lower Mach number, significant nonlinear distortions are produced. Phase cancellation is shown to be an effective mechanism for active boundary layer control.

  6. Response of osteosarcoma to preoperative intravenous high-dose methotrexate chemotherapy: CT evaluation

    SciTech Connect

    Mail, J.T.; Cohen, M.D.; Mirkin, L.D.; Provisor, A.J.

    1985-01-01

    The histologic response of an osteosarcoma to preamputation high-dose methotrexate therapy can be used to determine the optimum maintenance chemotherapy regimen to be administered after amputation. This study evaluates computed tomography (CT) as a method of assessing the response of the tumor to the methotrexate therapy. Nine patients with nonmetastatic osteosarcoma of an extremity had a CT scan of the tumor at initial presentation. This was compared with a second CT scan after four courses of high-dose intravenous methotrexate. Each set of scans was evaluated for changes in bony destruction, soft-tissue mass, pattern of calcification, and extent of tumor involvement of the marrow cavity. These findings were correlated with the histologic response of the tumor as measured by the degree of tumor necrosis. The changes seen on CT correlated well with the degree of the histologic response in seven of the nine patients.

  7. Enthalpy damping for high Mach number Euler solutions

    NASA Technical Reports Server (NTRS)

    Moitra, Anutosh

    1990-01-01

    An improvement on the enthalpy damping procedure currently in use in solving supersonic flow fields is described. A correction based on entropy values is shown to produce a very efficient scheme for simulation of high Mach number three-dimensional flows. Substantial improvements in convergence rates have been achieved by incorporating this enthalpy damping scheme in a finite-volume Runge-Kutta method for solving the Euler equations. Results obtained for blended wing-body geometries at very high Mach numbers are presented.

  8. High energy x-ray phase contrast CT using glancing-angle grating interferometers

    SciTech Connect

    Sarapata, A.; Stayman, J. W.; Siewerdsen, J. H.; Finkenthal, M.; Stutman, D.; Pfeiffer, F.

    2014-02-15

    Purpose: The authors present initial progress toward a clinically compatible x-ray phase contrast CT system, using glancing-angle x-ray grating interferometry to provide high contrast soft tissue images at estimated by computer simulation dose levels comparable to conventional absorption based CT. Methods: DPC-CT scans of a joint phantom and of soft tissues were performed in order to answer several important questions from a clinical setup point of view. A comparison between high and low fringe visibility systems is presented. The standard phase stepping method was compared with sliding window interlaced scanning. Using estimated dose values obtained with a Monte-Carlo code the authors studied the dependence of the phase image contrast on exposure time and dose. Results: Using a glancing angle interferometer at high x-ray energy (∼45 keV mean value) in combination with a conventional x-ray tube the authors achieved fringe visibility values of nearly 50%, never reported before. High fringe visibility is shown to be an indispensable parameter for a potential clinical scanner. Sliding window interlaced scanning proved to have higher SNRs and CNRs in a region of interest and to also be a crucial part of a low dose CT system. DPC-CT images of a soft tissue phantom at exposures in the range typical for absorption based CT of musculoskeletal extremities were obtained. Assuming a human knee as the CT target, good soft tissue phase contrast could be obtained at an estimated absorbed dose level around 8 mGy, similar to conventional CT. Conclusions: DPC-CT with glancing-angle interferometers provides improved soft tissue contrast over absorption CT even at clinically compatible dose levels (estimated by a Monte-Carlo computer simulation). Further steps in image processing, data reconstruction, and spectral matching could make the technique fully clinically compatible. Nevertheless, due to its increased scan time and complexity the technique should be thought of not as

  9. High energy x-ray phase contrast CT using glancing-angle grating interferometers

    PubMed Central

    Sarapata, A.; Stayman, J. W.; Finkenthal, M.; Siewerdsen, J. H.; Pfeiffer, F.; Stutman, D.

    2014-01-01

    Purpose: The authors present initial progress toward a clinically compatible x-ray phase contrast CT system, using glancing-angle x-ray grating interferometry to provide high contrast soft tissue images at estimated by computer simulation dose levels comparable to conventional absorption based CT. Methods: DPC-CT scans of a joint phantom and of soft tissues were performed in order to answer several important questions from a clinical setup point of view. A comparison between high and low fringe visibility systems is presented. The standard phase stepping method was compared with sliding window interlaced scanning. Using estimated dose values obtained with a Monte-Carlo code the authors studied the dependence of the phase image contrast on exposure time and dose. Results: Using a glancing angle interferometer at high x-ray energy (∼45 keV mean value) in combination with a conventional x-ray tube the authors achieved fringe visibility values of nearly 50%, never reported before. High fringe visibility is shown to be an indispensable parameter for a potential clinical scanner. Sliding window interlaced scanning proved to have higher SNRs and CNRs in a region of interest and to also be a crucial part of a low dose CT system. DPC-CT images of a soft tissue phantom at exposures in the range typical for absorption based CT of musculoskeletal extremities were obtained. Assuming a human knee as the CT target, good soft tissue phase contrast could be obtained at an estimated absorbed dose level around 8 mGy, similar to conventional CT. Conclusions: DPC-CT with glancing-angle interferometers provides improved soft tissue contrast over absorption CT even at clinically compatible dose levels (estimated by a Monte-Carlo computer simulation). Further steps in image processing, data reconstruction, and spectral matching could make the technique fully clinically compatible. Nevertheless, due to its increased scan time and complexity the technique should be thought of not as

  10. Vorticity transformation in high Karlovitz number premixed flames

    NASA Astrophysics Data System (ADS)

    Bobbitt, Brock; Lapointe, Simon; Blanquart, Guillaume

    2016-01-01

    To better understand the two-way coupling between turbulence and chemistry, the changes in turbulence characteristics through a premixed flame are investigated. Specifically, this study focuses on vorticity, ω, which is characteristic of the smallest length and time scales of turbulence, analyzing its behavior within and across high Karlovitz number (Ka) premixed flames. This is accomplished through a series of direct numerical simulations (DNS) of premixed n-heptane/air flames, modeled with a 35-species finite-rate chemical mechanism, whose conditions span a wide range of unburnt Karlovitz numbers and flame density ratios. The behavior of the terms in the enstrophy, ω2 = ω ṡ ω, transport equation is analyzed, and a scaling is proposed for each term. The resulting normalized enstrophy transport equation involves only a small set of parameters. Specifically, the theoretical analysis and DNS results support that, at high Karlovitz number, enstrophy transport obtains a balance of the viscous dissipation and production/vortex stretching terms. It is shown that, as a result, vorticity scales in the same manner as in homogeneous, isotropic turbulence within and across the flame, namely, scaling with the inverse of the Kolmogorov time scale, τη. As τη is a function only of the viscosity and dissipation rate, this work supports the validity of Kolmogorov's first similarity hypothesis in premixed turbulent flames for sufficiently high Ka numbers. Results are unaffected by the transport model, chemical model, turbulent Reynolds number, and finally the physical configuration.

  11. High Reynolds Number and Turbulence Effects on Turbine Heat Transfer

    NASA Technical Reports Server (NTRS)

    Yeh, Frederick C.; Hippensteele, Steven A.; vanFossen, G. James; Poinsatte, Philip E.; Ameri, Ali

    1994-01-01

    Experimental data on pressure distribution and heat transfer on a turbine airfoil were obtained over a range of Reynolds numbers from 0.75 to 7.0 x 10(exp 6) and a range of turbulence intensities from 1.8 to about 15%. The purpose of this study was to obtain fundamental heat transfer and pressure distribution data over a wide range of high Reynolds numbers and to extend the heat transfer data base to include the range or Reynolds numbers encountered in the Space Shuttle main engine turbopump turbines. The results of this study indicated that Reynolds number and turbulence intensity have a large effect on both the transition from laminar to turbulent flow and the resulting heat transfer. For a given turbulence intensity, heat transfer for all Reynolds numbers at the leading edge can generally be correlated with the Frossling number developed for lower Reynolds numbers. For a given turbulence intensity, heat transfer for the airfoil surfaces downstream of the leading edge can be approximately correlated with a dimensionless parameter. Comparisons of the experimental results were also made with a numerical solution from a two-dimensional Navier-Stokes code.

  12. Iterative reconstruction optimisations for high angle cone-beam micro-CT

    NASA Astrophysics Data System (ADS)

    Recur, B.; Fauconneau, M.; Kingston, A.; Myers, G.; Sheppard, A.

    2014-09-01

    We address several acquisition questions that have arisen for the high cone-angle helical-scanning micro-CT facility developed at the Australian National University. These challenges are generally known in medical and industrial cone-beam scanners but can be neglected in these systems. For our large datasets, with more than 20483 voxels, minimising the number of operations (or iterations) is crucial. Large cone-angles enable high signal-to-noise ratio imaging and a large helical pitch to be used. This introduces two challenges: (i) non-uniform resolution throughout the reconstruction, (ii) over-scan beyond the region-of-interest significantly increases re- quired reconstructed volume size. Challenge (i) can be addressed by using a double-helix or lower pitch helix but both solutions slow down iterations. Challenge (ii) can also be improved by using a lower pitch helix but results in more projections slowing down iterations. This may be overcome using less projections per revolution but leads to more iterations required. Here we assume a given total time for acquisition and a given reconstruction technique (SART) and seek to identify the optimal trajectory and number of projections per revolution in order to produce the best tomogram, minimise reconstruction time required, and minimise memory requirements.

  13. Probability density distribution of velocity differences at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Praskovsky, Alexander A.

    1993-01-01

    Recent understanding of fine-scale turbulence structure in high Reynolds number flows is mostly based on Kolmogorov's original and revised models. The main finding of these models is that intrinsic characteristics of fine-scale fluctuations are universal ones at high Reynolds numbers, i.e., the functional behavior of any small-scale parameter is the same in all flows if the Reynolds number is high enough. The only large-scale quantity that directly affects small-scale fluctuations is the energy flux through a cascade. In dynamical equilibrium between large- and small-scale motions, this flux is equal to the mean rate of energy dissipation epsilon. The pdd of velocity difference is a very important characteristic for both the basic understanding of fully developed turbulence and engineering problems. Hence, it is important to test the findings: (1) the functional behavior of the tails of the probability density distribution (pdd) represented by P(delta(u)) is proportional to exp(-b(r) absolute value of delta(u)/sigma(sub delta(u))) and (2) the logarithmic decrement b(r) scales as b(r) is proportional to r(sup 0.15) when separation r lies in the inertial subrange in high Reynolds number laboratory shear flows.

  14. Nonadiabatic electron heating at high-Mach-number perpendicular shocks

    NASA Technical Reports Server (NTRS)

    Tokar, R. L.; Aldrich, C. H.; Forslund, D. W.; Quest, K. B.

    1986-01-01

    Fully kinetic simulations of high-Mach-number (HMN) perpendicular collisionless shocks are described. It is shown that electron acceleration in the cross-shock electron field can produce downstream electron temperature significantly higher than those expected for adiabatic compression. The momentum space for test electrons at Mach 6 is illustrated.

  15. Wire-number effects on high-power annular z-pinches and some characteristics at high wire number

    SciTech Connect

    SANFORD,THOMAS W. L.

    2000-05-23

    Characteristics of annular wire-array z-pinches as a function of wire number and at high wire number are reviewed. The data, taken primarily using aluminum wires on Saturn are comprehensive. The experiments have provided important insights into the features of wire-array dynamics critical for high x-ray power generation, and have initiated a renaissance in z-pinches when high numbers of wires are used. In this regime, for example, radiation environments characteristic of those encountered during the early pulses required for indirect-drive ICF ignition on the NIF have been produced in hohlraums driven by x-rays from a z-pinch, and are commented on here.

  16. Aerodynamic and acoustic performance of high Mach number inlets

    NASA Technical Reports Server (NTRS)

    Lumsdaine, E.; Clark, L. R.; Cherng, J. C.; Tag, I.

    1977-01-01

    Experimental results were obtained for two types of high Mach number inlets, one with a translating centerbody and one with a fixed geometry (collapsing cowl) without centerbody. The aerodynamic and acoustic performance of these inlets was examined. The effects of several parameters such as area ratio and length-diameter ratio were investigated. The translating centerbody inlet was found to be superior to the collapsing cowl inlet both acoustically and aerodynamically, particularly for area ratios greater than 1.5. Comparison of length-diameter ratio and area ratio effects on performance near choked flow showed the latter parameter to be more significant. Also, greater high frequency noise attenuation was achieved by increasing Mach number from low to high subsonic values.

  17. Numerical solution of compressible viscous flows at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Maccormack, R. W.

    1981-01-01

    A new numerical method which was used to reduce the computation time required in fluid dynamics to solve the Navier-Stokes equations at flight Reynolds numbers is described. The method is the implicit analogue of the explicit finite different method. It uses this as its first stage, while the second stage removes the restrictive stability condition by recasting the difference equations in an implicit form. The resulting matrix equations to be solved are either upper or lower block bidiagonal equations. The new method makes it possible and practical to calculate many important three dimensional, high Reynolds number flow fields on computers.

  18. Very high Mach number shocks - Theory. [in space plasmas

    NASA Technical Reports Server (NTRS)

    Quest, Kevin B.

    1986-01-01

    The theory and simulation of collisionless perpendicular supercritical shock structure is reviewed, with major emphasis on recent research results. The primary tool of investigation is the hybrid simulation method, in which the Newtonian orbits of a large number of ion macroparticles are followed numerically, and in which the electrons are treated as a charge neutralizing fluid. The principal results include the following: (1) electron resistivity is not required to explain the observed quasi-stationarity of the earth's bow shock, (2) the structure of the perpendicular shock at very high Mach numbers depends sensitively on the upstream value of beta (the ratio of the thermal to magnetic pressure) and electron resistivity, (3) two-dimensional turbulence will become increasingly important as the Mach number is increased, and (4) nonadiabatic bulk electron heating will result when a thermal electron cannot complete a gyrorbit while transiting the shock.

  19. A High Spatial Resolution CT Scanner for Small Animal Imaging

    NASA Astrophysics Data System (ADS)

    Cicalini, E.; Baldazzi, G.; Belcari, N.; Del Guerra, A.; Gombia, M.; Motta, A.; Panetta, D.

    2006-01-01

    We have built a micro-CT system that will be integrated with a small animal PET scanner. The components are: an X-ray source with a peak voltage of up to 60 kV, a power of 10 W and a focal spot size of 30 μm; a CCD coupled to CsI(Tl) scintillator, subdivided into 128×3072 square pixels, each with a size of 48 μm; stepping motors for the sample roto-translation; a PCI acquisition board; electronic boards to control and read-out the CCD. A program in Lab VIEW controls the data acquisition. Reconstruction algorithms have been implemented for fan-beam and cone-beam configurations. Images of a bar pattern have been acquired to evaluate the detector performance: the CTF curve has been extracted from the data, obtaining a value of 10 % at 5 lp/mm and about 3 % at 10 lp/mm. Tomographic acquisitions have been performed with a test phantom consisting of a Plexiglas cylinder, 3 cm in diameter, with holes ranging from 3 mm down to 0.6 mm in diameter, filled with different materials. The contrast resolution has been extracted from the reconstructed images: a value of 6 % (in water) for a cubic voxel size of 80 μm has been obtained.

  20. Turbulence measurements in high Reynolds number boundary layers

    NASA Astrophysics Data System (ADS)

    Vallikivi, Margit; Smits, Alexander

    2013-11-01

    Measurements are conducted in zero pressure gradient turbulent boundary layers for Reynolds numbers from Reθ = 9,000 to 225,000. The experiments were performed in the High Reynolds number Test Facility (HRTF) at Princeton University, which uses compressed air as the working fluid. Nano-Scale Thermal Anemometry Probes (NSTAPs) are used to acquire data with very high spatial and temporal precision. These new data are used to study the scaling behavior of the streamwise velocity fluctuations in the boundary layer and make comparisons with the scaling of other wall-bounded turbulent flows. Supported under ONR Grant N00014-09-1-0263 (program manager Ron Joslin) and NSF Grant CBET-1064257 (program manager Henning Winter).

  1. High Reynolds Number Transition Experiments in ETW (TELFONA project)

    NASA Astrophysics Data System (ADS)

    Perraud, J.; Archambaud, J.-P.; Schrauf, G.; Donelli, R. S.; Hanifi, A.; Quest, J.; Hein, S.; Streit, T.; Fey, U.; Egami, Y.

    A wind-tunnel experiment on laminar-turbulent transition has been performed in ETW (the European Transonic Wind Tunnel in Koln) at high Reynolds number and cryogenic conditions. The studied geometry is a sting mounted full model in swept-wing configuration. The transition location was determined by means of Temperature Sensitive Paint (CryoTSP). The experimental observations were further analysed using different transition prediction tools, based on linear stability theory.

  2. High-pitch spiral acquisition: a new scan mode for coronary CT angiography.

    PubMed

    Achenbach, Stephan; Marwan, Mohamed; Schepis, Tiziano; Pflederer, Tobias; Bruder, Herbert; Allmendinger, Thomas; Petersilka, Martin; Anders, Katharina; Lell, Michael; Kuettner, Axel; Ropers, Dieter; Daniel, Werner G; Flohr, Thomas

    2009-01-01

    Coronary CT angiography allows high-quality imaging of the coronary arteries when state-of-the-art CT systems are used. However, radiation exposure has been a concern. We describe a new scan mode that uses a very high-pitch spiral acquisition, "Flash Spiral," which has been developed specifically for low-dose imaging with dual-source CT. The scan mode uses a pitch of 3.2 to acquire a spiral CT data set, while covering the entire volume of the heart in one cardiac cycle. Data acquisition is prospectively triggered by the electrocardiogram and starts in late systole to be completed within one cardiac cycle. Images are reconstructed with a temporal resolution that corresponds to one-quarter of the gantry rotation time. Throughout the data set, subsequent images are reconstructed at later time instants in the cardiac cycle. In a patient with a heart rate of 49 beats/min, the Flash Spiral scan mode was used with a first-generation dual-source CT system and allowed artifact-free visualization of the coronary arteries with a radiation exposure of 1.7 mSv for a 12-cm scan range at 120 kVp tube voltage. PMID:19332343

  3. Numerical Simulation of a High Mach Number Jet Flow

    NASA Technical Reports Server (NTRS)

    Hayder, M. Ehtesham; Turkel, Eli; Mankbadi, Reda R.

    1993-01-01

    The recent efforts to develop accurate numerical schemes for transition and turbulent flows are motivated, among other factors, by the need for accurate prediction of flow noise. The success of developing high speed civil transport plane (HSCT) is contingent upon our understanding and suppression of the jet exhaust noise. The radiated sound can be directly obtained by solving the full (time-dependent) compressible Navier-Stokes equations. However, this requires computational storage that is beyond currently available machines. This difficulty can be overcome by limiting the solution domain to the near field where the jet is nonlinear and then use acoustic analogy (e.g., Lighthill) to relate the far-field noise to the near-field sources. The later requires obtaining the time-dependent flow field. The other difficulty in aeroacoustics computations is that at high Reynolds numbers the turbulent flow has a large range of scales. Direct numerical simulations (DNS) cannot obtain all the scales of motion at high Reynolds number of technological interest. However, it is believed that the large scale structure is more efficient than the small-scale structure in radiating noise. Thus, one can model the small scales and calculate the acoustically active scales. The large scale structure in the noise-producing initial region of the jet can be viewed as a wavelike nature, the net radiated sound is the net cancellation after integration over space. As such, aeroacoustics computations are highly sensitive to errors in computing the sound sources. It is therefore essential to use a high-order numerical scheme to predict the flow field. The present paper presents the first step in a ongoing effort to predict jet noise. The emphasis here is in accurate prediction of the unsteady flow field. We solve the full time-dependent Navier-Stokes equations by a high order finite difference method. Time accurate spatial simulations of both plane and axisymmetric jet are presented. Jet Mach

  4. Wall-bounded turbulence at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Vallikivi, Margit

    Measurements are reported that give new insight into the behavior of turbulent wall-bounded flows at high Reynolds number. Turbulent pipe and boundary layer flows are examined experimentally over a wide range of Reynolds numbers -- up to Retau=100,000 (Re D=6x106) in pipe flow, and up to Re tau=73,000 (ReD=235x103) in a flat plate zero pressure gradient boundary layer. A Nano-Scale Thermal Anemometry Probe (NSTAP) was developed for very high spatial and temporal resolution measurements. Sensors with wire lengths 30 and 60 mum were fabricated, tested and validated in known flows, and then used to obtain single-point measurements at high Reynolds numbers in pipe and boundary layers. The mean velocity data together with data from previous studies and extensive error analysis showed that the von Karman's constant in the log-law is kappa=0.40+/-0.02. It was shown that the streamwise Reynolds stress exhibits a logarithmic behavior in the inertial sublayer for Retau≥20,000, in both pipes and boundary layers. Variances as well as higher order even moments were compared for pipes and boundary layers and it was shown that all even moments have a logarithmic behavior in the inertial sublayer, suggesting a true scale separation. Streamwise turbulent spectra showed a clear k --5/3 region for up to two decades in wavenumber. No k--1 region was found to be present in any of the cases in the pipe or the boundary layer. The location of the outer spectral peak, associated with very large scale motions, was found to have only a weak dependence on Reynolds number. The loci of these peak occur at the same wall-normal distance where the streamwise stresses establish a logarithmic behavior and where the amplitude modulation coefficient has a zero value. This suggests that with Reynolds number increasing to infinity most of the energy is contained within a diminishing wall-layer in physical coordinates.

  5. Reynolds Number Effects at High Angles of Attack

    NASA Technical Reports Server (NTRS)

    Fisher, David F.; Cobleigh, Brent R.; Banks, Daniel W.; Hall, Robert M.; Wahls, Richard A.

    1998-01-01

    Lessons learned from comparisons between ground-based tests and flight measurements for the high-angle-of-attack programs on the F-18 High Alpha Research Vehicle (HARV), the X-29 forward-swept wing aircraft, and the X-31 enhanced fighter maneuverability aircraft are presented. On all three vehicles, Reynolds number effects were evident on the forebodies at high angles of attack. The correlation between flight and wind tunnel forebody pressure distributions for the F-18 HARV were improved by using twin longitudinal grit strips on the forebody of the wind-tunnel model. Pressure distributions obtained on the X-29 wind-tunnel model at flight Reynolds numbers showed excellent correlation with the flight data up to alpha = 50 deg. Above (alpha = 50 deg. the pressure distributions for both flight and wind tunnel became asymmetric and showed poorer agreement, possibly because of the different surface finish of the model and aircraft. The detrimental effect of a very sharp nose apex was demonstrated on the X-31 aircraft. Grit strips on the forebody of the X-31 reduced the randomness but increased the magnitude of the asymmetry. Nose strakes were required to reduce the forebody yawing moment asymmetries and the grit strips on the flight test noseboom improved the aircraft handling qualities.

  6. A moving frame algorithm for high Mach number hydrodynamics

    NASA Astrophysics Data System (ADS)

    Trac, Hy; Pen, Ue-Li

    2004-07-01

    We present a new approach to Eulerian computational fluid dynamics that is designed to work at high Mach numbers encountered in astrophysical hydrodynamic simulations. Standard Eulerian schemes that strictly conserve total energy suffer from the high Mach number problem and proposed solutions to additionally solve the entropy or thermal energy still have their limitations. In our approach, the Eulerian conservation equations are solved in an adaptive frame moving with the fluid where Mach numbers are minimized. The moving frame approach uses a velocity decomposition technique to define local kinetic variables while storing the bulk kinetic components in a smoothed background velocity field that is associated with the grid velocity. Gravitationally induced accelerations are added to the grid, thereby minimizing the spurious heating problem encountered in cold gas flows. Separately tracking local and bulk flow components allows thermodynamic variables to be accurately calculated in both subsonic and supersonic regions. A main feature of the algorithm, that is not possible in previous Eulerian implementations, is the ability to resolve shocks and prevent spurious heating where both the pre-shock and post-shock fluid are supersonic. The hybrid algorithm combines the high-resolution shock capturing ability of the second-order accurate Eulerian TVD scheme with a low-diffusion Lagrangian advection scheme. We have implemented a cosmological code where the hydrodynamic evolution of the baryons is captured using the moving frame algorithm while the gravitational evolution of the collisionless dark matter is tracked using a particle-mesh N-body algorithm. Hydrodynamic and cosmological tests are described and results presented. The current code is fast, memory-friendly, and parallelized for shared-memory machines.

  7. High Order Difference Method for Low Mach Number Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Mueller, B.; Yee, H. C.; Mansour, Nagi (Technical Monitor)

    2001-01-01

    A high order finite difference method with improved accuracy and stability properties for computational aeroacoustics (CAA) at low Mach numbers is proposed. The Euler equations are split into a conservative and a symmetric non- conservative portion to allow the derivation of a generalized energy estimate. Since the symmetrization is based on entropy variables, that splitting of the flux derivatives is referred to as entropy splitting. Its discretization by high order central differences was found to need less numerical dissipation than conventional conservative schemes. Owing to the large disparity of acoustic and stagnation quantities in low Mach number aeroacoustics, the split Euler equations are formulated in perturbation form. The unknowns are the small changes of the conservative variables with respect to their large stagnation values. All nonlinearities and the conservation form of the conservative portion of the split flux derivatives can be retained, while cancellation errors are avoided with its discretization opposed to the conventional conservative form. The finite difference method is third-order accurate at the boundary and the conventional central sixth-order accurate stencil in the interior. The difference operator satisfies the summation by parts property analogous to the integration by parts in the continuous energy estimate. Thus, strict stability of the difference method follows automatically. Spurious high frequency oscillations are suppressed by a characteristic-based filter similar to but without limiter. The time derivative is approximated by a 4-stage low-storage second-order explicit Runge-Kutta method. The method has been applied to simulate vortex sound at low Mach numbers. We consider the Kirchhoff vortex, which is an elliptical patch of constant vorticity rotating with constant angular frequency in irrotational flow. The acoustic pressure generated by the Kirchhoff vortex is governed by the 2D Helmholtz equation, which can be solved

  8. Implicit turbulence modeling for high reynolds number flows.

    SciTech Connect

    Margolin, L. G.; Smolarkiewicz, P. K.; Wyszogrodzki, A. A.

    2001-01-01

    We continue our investigation of the implicit turbulence modeling property of the nonoscillatory finite volume scheme MPDATA. We start by comparing MPDATA simulations of decaying turbulence in a triply periodic cube with analogous pseudospectral studies. In the regime of direct numerical simulation, MPDATA is shown to agree closely with the pseudospectral model. As viscosity is reduced, the two model results diverge. We study the MPDATA results in the inviscid limit, using a combination of mathematical analysis and computational experiment. We validate the inviscid MPDATA results as representing the turbulent flow in the limit of very high Reynolds number.

  9. Wave phenomena in a high Reynolds number compressible boundary layer

    NASA Technical Reports Server (NTRS)

    Bayliss, A.; Maestrello, L.; Parikh, P.; Turkel, E.

    1987-01-01

    The behavior of spatially unstable waves in a high Reynolds number compressible laminar boundary layer is investigated by solution of the laminar two-dimensional compressible Navier-Stokes equations (solved to fourth-order accuracy) over a flat plate with a fluctuating disturbance generated at the inflow. A significant nonlinear distortion is produced, in qualitative agreement with experimental data. It is shown that increasing compressibility can significantly stabilize the flow over a flat plate, and that the mechanism of phase cancellation is a viable mechanism for the control of growing disturbances.

  10. Local isotropy in high Reynolds number turbulent shear flows

    NASA Technical Reports Server (NTRS)

    Saddoughi, Seyed G.

    1993-01-01

    This is a report on the continuation of experiments, which Dr. Srinivas Veeravalli and the present author started in 1991, to investigate the hypothesis of local isotropy in shear flows. This hypothesis, which states that at sufficiently high Reynolds numbers the small-scale structures of turbulent motions are independent of large-scale structures and mean deformations, has been used in theoretical studies of turbulence and computational methods like large-eddy simulation. The importance of Kolmogorov's ideas arises from the fact that they create a foundation for turbulence theory.

  11. Axisymmetric bubble pinch-off at high Reynolds numbers.

    PubMed

    Gordillo, J M; Sevilla, A; Rodríguez-Rodríguez, J; Martínez-Bazán, C

    2005-11-01

    Analytical considerations and potential-flow numerical simulations of the pinch-off of bubbles at high Reynolds numbers reveal that the bubble minimum radius, rn, decreases as tau proportional to r2n sqrt[1lnr2n], where tau is the time to break up, when the local shape of the bubble near the singularity is symmetric. However, if the gas convective terms in the momentum equation become of the order of those of the liquid, the bubble shape is no longer symmetric and the evolution of the neck changes to a rn proportional to tau1/3 power law. These findings are verified experimentally. PMID:16383983

  12. Anisotropic Structure of Rotating Homogeneous Turbulence at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Cambon, Claude; Mansour, Nagi N.; Squires, Kyle D.; Rai, Man Mohan (Technical Monitor)

    1995-01-01

    Large eddy simulation is used to investigate the development of anisotropies and the evolution towards a quasi two-dimensional state in rotating homogeneous turbulence at high Reynolds number. The present study demonstrates the existence of two transitions in the development of anisotropy. The first transition marks the onset of anisotropy and occurs when a macro-Rossby number (based on a longitudinal integral lengthscale) has decreased to near unity while the second transition occurs when a micro-Rossby number (defined in this work as the ratio of the rms fluctuating vorticity to background vorticity) has decreased to unity. The anisotropy marked by the first transition corresponds to a reduction in dimensionality while the second transition corresponds to a polarization of the flow, i.e., relative dominance of the velocity components in the plane normal to the rotation axis. Polarization is reflected by emergence of anisotropy measures based on the two-dimensional component of the turbulence. Investigation of the vorticity structure shows that the second transition is also characterized by an increasing tendency for alignment between the fluctuating vorticity vector and the background angular velocity vector with a preference for corrotative vorticity.

  13. Simulations of high Mach number perpendicular shocks with resistive electrons

    NASA Technical Reports Server (NTRS)

    Quest, K. B.

    1986-01-01

    A simulation code which models the ions as microparticles and the electrons as a resistive massless fluid is employed to study the structure of high Mach number perpendicular shocks. It is found that stable stationary shock solutions can be obtained for Alfven Mach numbers (M sub A) between 5 and 60 for upstream plasmas where the ratio of the plasma pressure to the magnetic pressure is 1, providing that the upstream resistive diffusion length is much smaller than the ion inertial length. For much larger resistive diffusion lengths, the magnetic field overshoot is damped, and the imbalance in the electron momentum equation results in a periodic fluctuation of the fraction of reflected ions. In the limit of M sub A of less than 10, the magnetic overshoot and the fraction of reflected ions increase with increasing M sub A, while at higher Mach numbers the fraction of reflected ions peaks at about 40 percent and the magnetic field overshoot increases at a much slower rate. Electron inertial effects are also considered.

  14. Resistance of plates and pipes at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Schiller, L; Hermann, R

    1931-01-01

    It was learned that the law of resistance for high R values does not follow the simple powers, and that the powers, which can be obtained approximately for the velocity distribution, gradually change. Since, moreover, very important investigations have recently been made on the resistance of plates at very high R values, it seemed of interest to apply the above line of reasoning to the new general law of resistance. For this purpose, the resistance and velocity distribution along the plate must always be equal to the values of the pipe flow at the corresponding Reynolds number. We made two kinds of calculations, of which the one given here is the simpler and more practical and also agrees better with the experimental results.

  15. Octane number requirements of vehicles at high altitude

    SciTech Connect

    Callison, J.C.

    1987-01-01

    Past tests of vehicles show that their octane number requirements decrease with altitude. As a result, gasoline marketers sell lower-octane-number(ON) gasoline in the mountain states and other high-altitude areas. The current ASTM specifications, which allow reduction of gasoline octane of 1.0 to 1.5 ON per thousand feet, are based on CRC test programs run on 1967 to 1972 model vehicles. However, many new vehicles are now equipped with sophisticated electronic engine systems for control of emissions and improvement of performance and fuel economy at all altitudes. Because these new systems could minimize the altitude effect on octane requirement, Amoco Oil tested twelve 1984-1986 model cars and light trucks. The authors found their ON requirements were reduced on average about 0.2 ON per thousand feet on an (R+M)/2 basis (RMON/1,000 feet). The authors expect octane demand on gasoline suppliers in high-altitude areas to increase as these new cars make up a larger part of the vehicle population, and this could raise the cost of gasoline.

  16. Virtual Monochromatic Images from Dual-Energy Multidetector CT: Variance in CT Numbers from the Same Lesion between Single-Source Projection-based and Dual-Source Image-based Implementations.

    PubMed

    Mileto, Achille; Barina, Andrew; Marin, Daniele; Stinnett, Sandra S; Roy Choudhury, Kingshuk; Wilson, Joshua M; Nelson, Rendon C

    2016-04-01

    Purpose To determine the variance in virtual monochromatic computed tomography (CT) numbers from the same lesion, comparing the two clinically available dual-energy multidetector CT hardware implementations (single-source projection-based and dual-source image-based), in a phantom-based simulated abdominal environment. Materials and Methods This phantom-based study was exempt from institutional review board oversight. Polyethylene terephthalate spheres (15 and 18 mm) with two iodine-to-saline dilutions (0.8 and 1.2 mg of iodine per millilliter) were serially suspended in a cylindrical polypropylene bottle filled with diluted iodinated contrast material. The bottle was placed into a 36-cm-wide torso-shaped water phantom simulating the abdomen of a medium-sized patient. Dual-energy (80/140 kVp) and single-energy (100 and 120 kVp) scans were obtained with single-source and dual-source multidetector CT implementations. Virtual monochromatic images were reconstructed at energy levels of 40-140 keV (in 10-keV increments) in either the projection-space or image-space domain. A multivariate regression analysis approach was used to investigate the effect of energy level, lesion size, lesion iodine content, and implementation type on measured CT numbers. Results There were significant differences in the attenuation values measured in the simulated lesions with the single-source projection-based platform and the dual-source image-based implementation (P < .001 for all comparisons). The magnitude of these differences was greatest at lower monochromatic energy levels and at lower iodine concentrations (average difference at 40 keV: 25.7 HU; average difference at 140 keV: 7 HU). The monochromatic energy level and the lesion iodine concentration had a significant effect on the difference in the measured attenuation values between the two implementations, which indicates that the two imaging platforms respond differently to changes in investigated variables (P < .001 for all

  17. "High-precision, reconstructed 3D model" of skull scanned by conebeam CT: Reproducibility verified using CAD/CAM data.

    PubMed

    Katsumura, Seiko; Sato, Keita; Ikawa, Tomoko; Yamamura, Keiko; Ando, Eriko; Shigeta, Yuko; Ogawa, Takumi

    2016-01-01

    Computed tomography (CT) scanning has recently been introduced into forensic medicine and dentistry. However, the presence of metal restorations in the dentition can adversely affect the quality of three-dimensional reconstruction from CT scans. In this study, we aimed to evaluate the reproducibility of a "high-precision, reconstructed 3D model" obtained from a conebeam CT scan of dentition, a method that might be particularly helpful in forensic medicine. We took conebeam CT and helical CT images of three dry skulls marked with 47 measuring points; reconstructed three-dimensional images; and measured the distances between the points in the 3D images with a computer-aided design/computer-aided manufacturing (CAD/CAM) marker. We found that in comparison with the helical CT, conebeam CT is capable of reproducing measurements closer to those obtained from the actual samples. In conclusion, our study indicated that the image-reproduction from a conebeam CT scan was more accurate than that from a helical CT scan. Furthermore, the "high-precision reconstructed 3D model" facilitates reliable visualization of full-sized oral and maxillofacial regions in both helical and conebeam CT scans. PMID:26832374

  18. CT imaging of the internal human ear: Test of a high resolution scanner

    NASA Astrophysics Data System (ADS)

    Bettuzzi, M.; Brancaccio, R.; Morigi, M. P.; Gallo, A.; Strolin, S.; Casali, F.; Lamanna, Ernesto; Ariù, Marilù

    2011-08-01

    During the course of 2009, in the framework of a project supported by the National Institute of Nuclear Physics, a number of tests were carried out at the Department of Physics of the University of Bologna in order to achieve a good quality CT scan of the internal human ear. The work was carried out in collaboration with the local “S. Orsola” Hospital in Bologna and a company (CEFLA) already involved in the production and commercialization of a CT scanner dedicated to dentistry. A laboratory scanner with a simple concept detector (CCD camera-lens-mirror-scintillator) was used to see to what extent it was possible to enhance the quality of a conventional CT scanner when examining the internal human ear. To test the system, some conventional measurements were made, such as the spatial resolution calculation with the MTF and dynamic range evaluation. Different scintillators were compared to select the most suitable for the purpose. With 0.5 mm thick structured cesium iodide and a field of view of 120×120 mm2, a spatial resolution of 6.5l p/mm at 5% MTF was obtained. The CT of a pair of human head phantoms was performed at an energy of 120 kVp. The first phantom was a rough representation of the human head shape, with soft tissue made of coarse slabs of Lucite. Some inserts, like small aluminum cylinders and cubes, with 1 mm diameter drilled holes, were used to simulate the channels that one finds inside the human inner ear. The second phantom is a plastic PVC fused head with a real human cranium inside. The bones in the cranium are well conserved and the inner ear features, such as the cochlea and semicircular channels, are clearly detectable. After a number of CT tests we obtained good results as far as structural representation and channel detection are concerned. Some images of the 3D rendering of the CT volume are shown below. The doctors of the local hospital who followed our experimentation expressed their satisfaction. The CT was compared to a virtual

  19. Stratified wakes, the high Froude number approximation, and potential flow

    NASA Astrophysics Data System (ADS)

    Vasholz, David P.

    2011-12-01

    Properties of a steady wake generated by a body moving uniformly at constant depth through a stratified fluid are studied as a function of two parameters inserted into the linearized equations of motion. The first parameter, μ, multiplies the along-track gradient term in the source equation. When formal solutions for an arbitrary buoyancy frequency profile are written as eigenfunction expansions, one finds that the limit μ → 0 corresponds to a high Froude number approximation accompanied by a substantial reduction in the complexity of the calculation. For μ = 1, upstream effects are present and the eigenvalues correspond to critical speeds above which transverse waves disappear for any given mode. For sufficiently high modes, the high Froude number approximation is valid. The second tracer multiplies the square of the buoyancy frequency term in the linearized conservation of mass equation and enables direct comparisons with the limit of potential flow. Detailed results are given for the simplest possible profile, in which the buoyancy frequency is independent of depth; emphasis is placed upon quantities that can, in principle, be experimentally measured in a laboratory experiment. The vertical displacement field is written in terms of a stratified wake form factor {{H}} , which is the sum of a wavelike contribution that is non-zero downstream and an evanescent contribution that appears symmetrically upstream and downstream. First- and second-order cross-track moments of {{H}} are analyzed. First-order results predict enhanced upstream vertical displacements. Second-order results expand upon previous predictions of wavelike resonances and also predict evanescent resonance effects.

  20. Passive scalars in turbulent channel flow at high Reynolds number

    NASA Astrophysics Data System (ADS)

    Pirozzoli, Sergio; Bernardini, Matteo; Orlandi, Paolo

    2015-11-01

    We study passive scalars in turbulent plane channels at computationally high Reynolds number, which allows to observe previously unnoticed effects. The mean scalar profiles are found to obey a generalized logarithmic law which includes a linear correction term in the whole lower half-channel, and they follow a universal parabolic defect profile in the core region. This is consistent with recent findings regarding the mean velocity profiles in channel flow. The scalar variances also exhibit a near universal parabolic distribution in the core flow, and hints of a sizeable log layer, unlike the velocity variances. The energy spectra highlight the formation of large scalar-bearing eddies spanning each half-channel, which are caused by production excess over dissipation, and which are clearly visible in the flow visualizations. Close correspondence of the velocity and scalar eddies is observed, the main difference being that the latter have more convoluted interfaces, which translates into higher scalar dissipation. Another notable Reynolds number effect is the decreased correlation of the scalar field with the vertical velocity field, which is traced to the reduced effectiveness of ejection events. We acknowledge that the results reported in this paper have been achieved using the PRACE Research Infrastructure resource FERMI based at CINECA, Casalecchio di Reno, Italy.

  1. High-accuracy registration of intraoperative CT imaging

    NASA Astrophysics Data System (ADS)

    Oentoro, A.; Ellis, R. E.

    2010-02-01

    Image-guided interventions using intraoperative 3D imaging can be less cumbersome than systems dependent on preoperative images, especially by needing neither potentially invasive image-to-patient registration nor a lengthy process of segmenting and generating a 3D surface model. In this study, a method for computer-assisted surgery using direct navigation on intraoperative imaging is presented. In this system the registration step of a navigated procedure was divided into two stages: preoperative calibration of images to a ceiling-mounted optical tracking system, and intraoperative tracking during acquisition of the 3D medical image volume. The preoperative stage used a custom-made multi-modal calibrator that could be optically tracked and also contained fiducial spheres for radiological detection; a robust registration algorithm was used to compensate for the very high false-detection rate that was due to the high physical density of the optical light-emitting diodes. Intraoperatively, a tracking device was attached to plastic bone models that were also instrumented with radio-opaque spheres; A calibrated pointer was used to contact the latter spheres as a validation of the registration. Experiments showed that the fiducial registration error of the preoperative calibration stage was approximately 0.1 mm. The target registration error in the validation stage was approximately 1.2 mm. This study suggests that direct registration, coupled with procedure-specific graphical rendering, is potentially a highly accurate means of performing image-guided interventions in a fast, simple manner.

  2. High Reynolds number decay of turbulent Taylor-Couette flow

    NASA Astrophysics Data System (ADS)

    Verschoof, Ruben A.; Huisman, Sander G.; van der Veen, Roeland C. A.; Sun, Chao; Lohse, Detlef

    2015-11-01

    We study the decay of high-Reynolds number turbulence in a Taylor-Couette facility for pure inner cylinder rotation. The rotation of the inner cylinder (Rei = 2 ×106) is suddenly decelerated as fast as possible, thus removing the energy input within seconds. Local velocity measurements show that the decay in this wall-bounded inhomogeneous flow is faster than observed for homogeneous isotropic turbulent flows, due to the strong viscous drag applied by the inner and outer cylinder surfaces. We found that the decay over time can be described with the differential equation Re . (t) =cf (Re)Re2 , where the effects of the walls are included through the friction coefficient. A self-similar behavior of the azimuthal velocity is found: its normalized velocity profile as a function of the radius collapses over time during the decay process.

  3. Mixing of two miscible fluids at high Schmidt number

    NASA Astrophysics Data System (ADS)

    Simmons, Mark; Alberini, Federico; Pain, Christopher; Matar, Omar

    2013-11-01

    The blending of two miscible liquids at high Schmidt number is an increasingly common industrial problem: as processes push towards shorter timescales yet the rheology of the fluids becomes increasingly complex. This leads to phenomena which resemble a quasi two-phase system with zero interfacial tension. In this study, we compare experimental results with computational fluid dynamics simulations using unstructured-mesh adaptivity for the flow of two Newtonian, or two power-law fluids through a complex geometry representative of a Kenics type static mixer used in industry. The geometry induces a stretching and folding of the fluid elements which causes exponential growth of the interface length down the geometry. The interfacial topology obtained from the simulations is compared with experiments carried out using Planar Laser Induced Fluorescence (PLIF), which enables the spatial distribution of each phase, and the interfaces between them, to be determined at the outlet of the geometry. EPSRC Programme Grant EP/K003976/1.

  4. A High Altitude-Low Reynolds Number Aerodynamic Flight Experiment

    NASA Technical Reports Server (NTRS)

    Greer, Don; Krake, Keith; Hamory, Phil; Drela, Mark; Lee, Seunghee (Technical Monitor)

    1999-01-01

    A sailplane is currently being developed at NASA's Dryden Flight Research Center to support a high altitude flight experiment. The purpose of the experiment is to measure the performance characteristics of an airfoil at altitudes between 100,000 and 70,000 feet at Mach numbers between 0.65 and 0.5. The airfoil lift and drag are measured from pilot and static pressures. The location of the separation bubble and vortex shedding are measured from a hot film strip. The details of the flight experiment are presented. A comparison of several estimates of the airfoil performance is also presented. The airfoil, APEX-16, was designed by Drela (MIT) with his MSES code. A two dimensional Navier-Stokes analysis has been performed by Tatineni and Zhong (UCLA) and another at the Dryden Flight Research Center. The role these analysis served to define the experiment is discussed.

  5. Selective decay hypothesis at high mechanical and magnetic Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Matthaeus, W. H.; Montgomery, D.

    1980-12-01

    Implications of certain applications of turbulence theory to two-dimensional turbulence and magnetohydrodynamic flow are discussed. It is shown that the use of the Navier-Stokes equation (NSE) for measurements of turbulent fluctuations has been effective only for three-dimensional flows. For two-dimensional flows, used for the study of large-scale motions in the atmosphere or ocean, enstrophy is cascaded to high wave numbers and dissipated at a finite rate even at infinite Re. MHD flows are numerically calculated for the two-dimensional case and analytically for the three-dimensional case, for which discrepancies in the relative rates of energy and cross helicity decay lead to a recommendation that numerical calculations for the three-dimensional case be carried out to determine the precise decayed states.

  6. Experimental investigations of He II flows at high Reynolds number

    NASA Technical Reports Server (NTRS)

    Van Sciver, Steve W.

    1991-01-01

    Fluid dynamics studies of He II at high Reynolds number (Re(d) greater than 10 exp 6) reveal characteristics which are best interpreted in terms of classical scaling relationships. In particular, the smooth tube friction factor is seen to correlate with the Von Karman-Nikuradse formulation. Also, the performance of a centrifugal pump is unchanged whether being used with He I or He II. These effects are expected to result provided the He II possesses a viscous sublayer and that the drag is determined by laminar flow within this layer. On the other hand, heat transfer in He II is substantially different from that of He I because of the unique internal convection mechanism present in this quantum fluid. These experiments are performed in the University of Wisconsin liquid helium flow facility which has unique capabilities of He II temperature, pressure and flow.

  7. Magnetic resonance imaging assessed cortical porosity is highly correlated with μCT porosity

    PubMed Central

    Bae, Won C; Patil, Shantanu; Biswas, Reni; Li, Shihong; Chang, Eric Y; Statum, Sheronda; D'Lima, Darryl D; Chung, Christine B; Du, Jiang

    2014-01-01

    Cortical bone is typically regarded as “MR invisible” with conventional clinical magnetic resonance imaging (MRI) pulse sequences. However, recent studies have demonstrated that free water in the microscopic pores of cortical bone has a short T2* but a relatively long T2, and may be detectable with conventional clinical spin echo (SE) or fast spin echo (FSE) sequences. In this study we describe the use of a conventional two-dimensional (2D) FSE sequence to assess cortical bone microstructure and measure cortical porosity using a clinical 3T scanner. Twelve cadaveric human cortical bone samples were studied with MRI and micro computed tomography (μCT) (downsampled to the same spatial resolution). Preliminary results show that FSE-determined porosity is highly correlated (R2 = 0.83; P < 0.0001) with μCT porosity. Bland Altman analysis suggested a good agreement between FSE and μCT with tight limit of agreement at around 3%. There is also a small bias of -2% for the FSE data, which suggested that the FSE approach slightly underestimated μCT porosity. The results demonstrate that cortical porosity can be directly assessed using conventional clinical FSE sequences. The clinical feasibility of this approach was also demonstrated on six healthy volunteers using 2D FSE sequences as well as 2D ultrashort echo time (UTE) sequences with a minimal echo time (TE) of 8 μs, which provide high contrast imaging of cortical bone in vivo. PMID:24928498

  8. Exploring crystallization kinetics in natural rhyolitic melts using high resolution CT imagery of spherulites

    NASA Astrophysics Data System (ADS)

    Clow, T. W.; Befus, K. S.; Gardner, J. E.

    2014-12-01

    Little of our understanding of crystallization kinetics has been directly derived from studies of natural samples. We examine crystallization of rhyolitic melts by quantifying spherulite sizes and number densities in obsidian collected from Yellowstone caldera using high-resolution x-ray computed tomography (CT) imagery. Spherulites are spherical to ellipsoidal masses of intergrown alkali feldspar and quartz in a radiating, fibrous structure. They are thought to form in response to relatively rapid crystallization of melt in response to large amounts of undercooling. Recent research using compositional gradients that form outside of spherulites has suggested that they nucleate at 700 to 500 ˚C and their growth slows exponentially until it eventually ceases at ~400 ˚C. By quantifying spherulite textures, and using those temperature constraints, we derive new kinetic information regarding crystallization in natural rhyolitic systems. We find that spherulites range from 0.2 to 12.3 mm in diameter, and are 0.004 to 49.5 mm3 in volume. Such values generate number densities of 70 to 185 spherulites cm-3. Histograms of size display positively skewed distributions indicating small spherulites are far more abundant than larger ones. Those distributions imply nucleation rates change as a function of temperature. At higher temperatures where the melt is undercooled by 400-500 ˚C, nucleation is rare and growth is favored. With decreasing temperature, nucleation rates increase rapidly until cold enough temperatures are reached that diffusion limits crystallization and causes it to cease (undercoolings of ~650 ˚C). Assuming a cooling rate for the host obsidian of 10-5 ˚C s-1, then overall spherulite nucleation rates are 0.01 to 0.03 spherulites cm-3 hour-1.

  9. Low-dose high-resolution CT of lung parenchyma

    SciTech Connect

    Zwirewich, C.V.; Mayo, J.R.; Mueller, N.L. )

    1991-08-01

    To evaluate the efficacy of low-dose high-resolution computed tomography (HRCT) in the assessment of lung parenchyma, three observers reviewed the scans of 31 patients. The 1.5-mm-collimation, 2-second, 120-kVp scans were obtained at 20 and 200 mA at selected identical levels in the chest. The observers evaluated the visualization of normal pulmonary anatomy, various parenchymal abnormalities and their distribution, and artifacts. The low-dose and conventional scans were equivalent in the evaluation of vessels, lobar and segmental bronchi, and anatomy of secondary pulmonary lobules, and in characterizing the extent and distribution of reticulation, honeycomb cysts, and thickened interlobular septa. The low-dose technique failed to demonstrate ground-glass opacity in two of 10 cases (20%) and emphysema in one of nine cases (11%), in which they were evident but subtle on the high-dose scans. These differences were not statistically significant. Linear streak artifact was more prominent on images acquired with the low-dose technique, but the two techniques were judged equally diagnostic in 97% of cases. The authors conclude that HRCT images acquired at 20 mA yield anatomic information equivalent to that obtained with 200-mA scans in the majority of patients, without significant loss of spatial resolution or image degradation due to linear streak artifact.

  10. Turbomachinery for Low-to-High Mach Number Flight

    NASA Technical Reports Server (NTRS)

    Tan, Choon S.; Shah, Parthiv N.

    2004-01-01

    The thrust capability of turbojet cycles is reduced at high flight Mach number (3+) by the increase in inlet stagnation temperature. The 'hot section' temperature limit imposed by materials technology sets the maximum heat addition and, hence, sets the maximum flight Mach number of the operating envelope. Compressor pre-cooling, either via a heat exchanger or mass-injection, has been suggested as a means to reduce compressor inlet temperature and increase mass flow capability, thereby increasing thrust. To date, however, no research has looked at compressor cooling (i.e., using a compressor both to perform work on the gas path air and extract heat from it simultaneously). We wish to assess the feasibility of this novel concept for use in low-to-high Mach number flight. The results to-date show that an axial compressor with cooling: (1) relieves choking in rear stages (hence opening up operability), (2) yields higher-pressure ratio and (3) yields higher efficiency for a given corrected speed and mass flow. The performance benefit is driven: (i) at the blade passage level, by a decrease in the total pressure reduction coefficient and an increase in the flow turning; and (ii) by the reduction in temperature that results in less work required for a given pressure ratio. The latter is a thermodynamic effect. As an example, calculations were performed for an eight-stage compressor with an adiabatic design pressure ratio of 5. By defining non-dimensional cooling as the percentage of compressor inlet stagnation enthalpy removed by a heat sink, the model shows that a non-dimensional cooling of percent in each blade row of the first two stages can increase the compressor pressure ratio by as much as 10-20 percent. Maximum corrected mass flow at a given corrected speed may increase by as much as 5 percent. In addition, efficiency may increase by as much as 5 points. A framework for characterizing and generating the performance map for a cooled compressor has been developed

  11. NOTE: Ring artifact correction for high-resolution micro CT

    NASA Astrophysics Data System (ADS)

    Kyriakou, Yiannis; Prell, Daniel; Kalender, Willi A.; Gleich, B.; Borgert, J.; Buzug, T. M.

    2009-09-01

    Recently a new imaging technique called magnetic particle imaging was proposed. The method uses the nonlinear response of magnetic nanoparticles when a time varying magnetic field is applied. Spatial encoding is achieved by moving a field-free point through an object of interest while the field strength in the vicinity of the point is high. A resolution in the submillimeter range is provided even for fast data acquisition sequences. In this paper, a simulation study is performed on different trajectories moving the field-free point through the field of view. The purpose is to provide mandatory information for the design of a magnetic particle imaging scanner. Trajectories are compared with respect to density, speed and image quality when applied in data acquisition. Since simulation of the involved physics is a time demanding task, moreover, an efficient implementation is presented utilizing caching techniques.

  12. Substrate degradation in high-Rayleigh-number reactive convection

    NASA Astrophysics Data System (ADS)

    Ward, T. J.; Jensen, O. E.; Power, H.; Riley, D. S.

    2015-11-01

    We study buoyancy-induced convection of a solute in an ideal two-dimensional fluid-saturated porous medium, where the solute undergoes a second-order reaction with a chemical substrate that is fixed in the underlying matrix. Numerical simulations at high Rayleigh number show how a flow is established in which a thin dynamic boundary layer beneath the solute source feeds slender vertical plumes beneath. We examine how the substrate is reactively degraded, at a rate enhanced by convective mixing. For the case when the substrate is abundant, we derive a reduced-order model describing the slow degradation of the substrate, which is formulated as a novel one-dimensional free-boundary problem. Numerical simulations and the reduced model reveal how, when the reaction is rapid compared to the convective time scale, the plumes propagate deep into the flow domain with reaction confined to a narrow region at their base. In contrast, slow reaction allows plumes to fill the domain before degradation of the substrate proceeds homogeneously. An alternative model with a thin reaction front captures the rapid degradation of the substrate when the solute concentration is relatively high.

  13. Virtual histology by means of high-resolution X-ray CT.

    PubMed

    Cnudde, V; Masschaele, B; De Cock, H E V; Olstad, K; Vlaminck, L; Vlassenbroeck, J; Dierick, M; Witte, Y D; Van Hoorebeke, L; Jacobs, P

    2008-12-01

    Micro-CT is a non-destructive technique for 3D tomographic investigation of an object. A 3D representation of the internal structure is calculated based on a series of X-ray radiographs taken from different angles. The spatial resolution of current laboratory-used micro-CT systems has come down over the last years from a few tens of microns to a few microns. This opens the possibility to perform histological investigations in 3D on a virtual representation of a sample, referred to as virtual 3D histology. The advantage of micro-CT based virtual histology is the immediate and automated 3D visualization of the sample without prior slicing, sample preparation like decalcification, photographing and aligning. This not only permits a drastic reduction in preparation time but also offers the possibility to easily investigate objects that are difficult to slice. This article presents results that were obtained on punch biopsies of horse skin, (dental) alveolus of ponies and chondro-osseous samples from the tarsus of foals studied with the new high resolution micro-CT set-up (HRXCT) at the Ghent University (Belgium) (http://www.ugct.ugent.be). This state-of-the-art set-up provides a 1 micron resolution and is therefore ideally suited for a direct comparison with standard light microscopy-based histology. PMID:19094024

  14. The assessment of the role of baseline low-dose CT scan in patients at high risk of lung cancer

    PubMed Central

    Kołaczyk, Katarzyna; Walecka, Anna; Grodzki, Tomasz; Alchimowicz, Jacek; Smereczyński, Andrzej; Kiedrowicz, Radosław

    2014-01-01

    Summary Background Despite the progress in contemporary medicine comprising diagnostic and therapeutic methods, lung cancer is still one of the biggest health concerns in many countries of the world. The main purpose of the study was to evaluate the detection rate of pulmonary nodules and lung cancer in the initial, helical low-dose CT of the chest as well as the analysis of the relationship between the size and the histopathological character of the detected nodules. Material/Methods We retrospectively evaluated 1999 initial, consecutive results of the CT examinations performed within the framework of early lung cancer detection program initiated in Szczecin. The project enrolled persons of both sexes, aged 55–65 years, with at least 20 pack-years of cigarette smoking or current smokers. The analysis included assessment of the number of positive results and the evaluation of the detected nodules in relationship to their size. All of the nodules were classified into I of VI groups and subsequently compared with histopathological type of the neoplastic and nonneoplastic pulmonary lesions. Results Pulmonary nodules were detected in 921 (46%) subjects. What is more, malignant lesions as well as lung cancer were significantly, more frequently discovered in the group of asymptomatic nodules of the largest dimension exceeding 15 mm. Conclusions The initial, low-dose helical CT of the lungs performed in high risk individuals enables detection of appreciable number of indeterminate pulmonary nodules. In most of the asymptomatic patients with histopathologically proven pulmonary nodules greater than 15 mm, the mentioned lesions are malignant, what warrants further, intensified diagnostics. PMID:25057333

  15. Design of a high-resolution small-animal SPECT-CT system sharing a CdTe semiconductor detector

    NASA Astrophysics Data System (ADS)

    Ryu, Hyun-Ju; Lee, Young-Jin; Lee, Seung-Wan; Cho, Hyo-Min; Choi, Yu-Na; Kim, Hee-Joung

    2012-07-01

    A single photon emission computed tomography (SPECT) system with a co-registered X-y computed tomography (CT) system allows the convergence of functional information and morphologic information. The localization of radiopharmaceuticals on a SPECT can be enhanced by combining the SPECT with an anatomical modality, such as X-ray CT. Gamma-ray imaging for nuclear medicine devices and X-ray imaging systems for diagnostics has recently been developed based on semiconductor detectors, and semiconductor detector materials such as cadmium telluride (CdTe) or cadmium zinc telluride (CZT) are available for both X-ray and gamma-ray systems for small-animal imaging. CdTe or CZT detectors provide strong absorption and high detection efficiency of high energy X-ray and gamma-ray photons because of their large atomic numbers. In this study, a pinhole collimator SPECT system sharing a cadmium telluride (CdTe) detector with a CT was designed. The GEANT4 application for tomographic emission (GATE) v.6.1 was used for the simulation. The pinhole collimator was designed to obtain a high spatial resolution of the SPECT system. The acquisition time for each projection was 40 seconds, and 60 projections were obtained for tomographic image acquisition. The reconstruction was performed using ordered subset expectation maximization (OS-EM) algorithms. The sensitivity and the spatial resolution were measured on the GATE simulation to evaluate the system characteristics. The spatial resolution of the system calculated from the FWHM of Gaussian fitted PSF curve was 0.69 mm, and the sensitivity of the system was measured to be 0.354 cps/kBq by using a Tc-99m point source of 1 MBq for 800 seconds. A phantom study was performed to verify the design of the dual imaging modality system. The system will be built as designed, and it can be applied as a pre-clinical imaging system.

  16. Dynamics of Active Separation Control at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Pack, LaTunia G.; Seifert, Avi

    2000-01-01

    A series of active flow control experiments were recently conducted at high Reynolds numbers on a generic separated configuration. The model simulates the upper surface of a 20% thick Glauert-Goldschmied type airfoil at zero angle of attack. The flow is fully turbulent since the tunnel sidewall boundary layer flows over the model. The main motivation for the experiments is to generate a comprehensive data base for validation of unsteady numerical simulation as a first step in the development of a CFD design tool, without which it would not be possible to effectively utilize the great potential of unsteady flow control. This paper focuses on the dynamics of several key features of the baseline as well as the controlled flow. It was found that the thickness of the upstream boundary layer has a negligible effect on the flow dynamics. It is speculated that separation is caused mainly by the highly convex surface while viscous effects are less important. The two-dimensional separated flow contains unsteady waves centered on a reduced frequency of 0.8, while in the three dimensional separated flow, frequencies around a reduced frequency of 0.3 and 1 are active. Several scenarios of resonant wave interaction take place at the separated shear-layer and in the pressure recovery region. The unstable reduced frequency bands for periodic excitation are centered on 1.5 and 5, but these reduced frequencies are based on the length of the baseline bubble that shortens due to the excitation. The conventional swept wing-scaling works well for the coherent wave features. Reproduction of these dynamic effects by a numerical simulation would provide benchmark validation.

  17. Efficient simulation of detached flows at high Reynolds number

    NASA Astrophysics Data System (ADS)

    Vega, Jose M.; Asensio, Victor; Herrero, Raul; Varas, Fernando

    2014-11-01

    A method is presented for the computationally efficient simulation of quasi-periodic detached flows in multi-parameter problems at very large Reynolds numbers, keeping in mind a variety of applications, including helicopter flight simulators, control and certification of unmanned aerial vehicles, control of wind turbines, conceptual design in aeronautics, and civil aerodynamics. In many of these applications, the large scale flows (ignoring the smaller turbulent scales) are at most quasi-periodic, namely the Fourier transform exhibits a finite set of concentrated peaks resulting from the nonlinear passive interaction of periodic wakes. The method consists in an offline preprocess and the online operation. In the preprocess, a standard CFD solver (such as URANS) is used in combination with several ingredients such as an iterative combination proper orthogonal decomposition and fast Fourier transform. The online operation is made with a combination of high order singular value decomposition and interpolation. The performance of the method is tested considering the ow over a fairly complex urban topography, for various free stream intensities and orientations, seeking real time online simulations.

  18. Interaction of upstream flow distortions with high Mach number cascades

    NASA Technical Reports Server (NTRS)

    Englert, G. W.

    1981-01-01

    Features of the interaction of flow distortions, such as gusts and wakes with blade rows of advance type fans and compressors having high tip Mach numbers are modeled. A typical disturbance was assumed to have harmonic time dependence and was described, at a far upstream location, in three orthogonal spatial coordinates by a double Fourier series. It was convected at supersonic relative to a linear cascade described as an unrolled annulus. Conditions were selected so that the component of this velocity parallel to the axis of the turbomachine was subsonic, permitting interaction between blades through the upstream as well as downstream flow media. A strong, nearly normal shock was considered in the blade passages which was allowed curvature and displacement. The flows before and after the shock were linearized relative to uniform mean velocities in their respective regions. Solution of the descriptive equations was by adaption of the Wiener-Hopf technique, enabling a determination of distortion patterns through and downstream of the cascade as well as pressure distributions on the blade and surfaces. Details of interaction of the disturbance with the in-passage shock were discussed. Infuences of amplitude, wave length, and phase of the disturbance on lifts and moments of cascade configurations are presented. Numerical results are clarified by reference to an especially orderly pattern of upstream vertical motion in relation to the cascade parameters.

  19. Application of high resolution synchrotron micro-CT radiation in dental implant osseointegration.

    PubMed

    Neldam, Camilla Albeck; Lauridsen, Torsten; Rack, Alexander; Lefolii, Tore Tranberg; Jørgensen, Niklas Rye; Feidenhans'l, Robert; Pinholt, Else Marie

    2015-06-01

    The purpose of this study was to describe a refined method using high-resolution synchrotron radiation microtomography (SRmicro-CT) to evaluate osseointegration and peri-implant bone volume fraction after titanium dental implant insertion. SRmicro-CT is considered gold standard evaluating bone microarchitecture. Its high resolution, high contrast, and excellent high signal-to-noise-ratio all contribute to the highest spatial resolutions achievable today. Using SRmicro-CT at a voxel size of 5 μm in an experimental goat mandible model, the peri-implant bone volume fraction was found to quickly increase to 50% as the radial distance from the implant surface increased, and levelled out to approximately 80% at a distance of 400 μm. This method has been successful in depicting the bone and cavities in three dimensions thereby enabling us to give a more precise answer to the fraction of the bone-to-implant contact compared to previous methods. PMID:25957106

  20. Improving spatial-resolution in high cone-angle micro-CT by source deblurring

    NASA Astrophysics Data System (ADS)

    Li, Heyang; Kingston, Andrew; Myers, Glenn; Recur, Benoit; Turner, Michael; Sheppard, Andrian

    2014-09-01

    Micro scale computed tomography (CT) can resolve many features in cellular structures, bone formations, minerals properties and composite materials not seen at lower spatial-resolution. Those features enable us to build a more comprehensive model for the object of interest. CT resolution is limited by a fundamental trade off between source size and signal-to-noise ratio (SNR) for a given acquisition time. There is a limit on the X-ray flux that can be emitted from a certain source size, and fewer photons cause a lower SNR. A large source size creates penumbral blurring in the radiograph, limiting the effective spatial-resolution in the reconstruction. High cone-angle CT improves SNR by increasing the X-ray solid angle that passes through the sample. In the high cone-angle regime current source deblurring methods break down due to incomplete modelling of the physical process. This paper presents high cone-angle source de-blurring models. We implement these models using a novel multi-slice Richardson-Lucy (M-RL) and 3D Conjugate Gradient deconvolution on experimental high cone-angle data to improve the spatial-resolution of the reconstructed volume. In M-RL, we slice the back projection volume into subsets which can be considered to have a relative uniform convolution kernel. We compare these results to those obtained from standard reconstruction techniques and current source deblurring methods (i.e. 2D Richardson-Lucy in the radiograph and the volume respectively).

  1. CT of multiple sclerosis: reassessment of delayed scanning with high doses of contrast material

    SciTech Connect

    Spiegel, S.M.; Vinuela, F.; Fox, A.J.; Pelz, D.M.

    1985-09-01

    A prospective study involving 87 patients was carried out to evaluate the necessity for a high dose of contrast material in addition to delayed computed tomographic (CT) scanning for optimal detection of the lesions of multiple sclerosis in the brain. In patients with either clinically definite multiple sclerosis or laboratory-supported definite multiple sclerosis, CT scans were obtained with a uniform protocol. Lesions consistent with multiple sclerosis were demonstrated on the second scan in 54 patients. In 36 of these 54 patients, the high-dose delayed scan added information. These results are quite similar to those of a previous study from this institution using different patients, in whom the second scan was obtained immediately after the bolus injection of contrast material containing 40 g of organically bound iodine. The lack of real difference in the results of the two studies indicate that the increased dose, not just the delay in scanning, is necessary for a proper study.

  2. High resolution multidetector CT aided tissue analysis and quantification of lung fibrosis

    NASA Astrophysics Data System (ADS)

    Zavaletta, Vanessa A.; Karwoski, Ronald A.; Bartholmai, Brian; Robb, Richard A.

    2006-03-01

    Idiopathic pulmonary fibrosis (IPF, also known as Idiopathic Usual Interstitial Pneumontis, pathologically) is a progressive diffuse lung disease which has a median survival rate of less than four years with a prevalence of 15-20/100,000 in the United States. Global function changes are measured by pulmonary function tests and the diagnosis and extent of pulmonary structural changes are typically assessed by acquiring two-dimensional high resolution CT (HRCT) images. The acquisition and analysis of volumetric high resolution Multi-Detector CT (MDCT) images with nearly isotropic pixels offers the potential to measure both lung function and structure. This paper presents a new approach to three dimensional lung image analysis and classification of normal and abnormal structures in lungs with IPF.

  3. Toward Immersed Boundary Simulation of High Reynolds Number Flows

    NASA Technical Reports Server (NTRS)

    Kalitzin, Georgi; Iaccarino, Gianluca

    2003-01-01

    of high Reynolds number wall bounded flows is particularly challenging as it requires the consideration of thin turbulent boundary layers, i.e. near wall regions with large gradients of the flow field variables. For such flows, the representation of the wall boundary has a large impact on the accuracy of the computation. It is also critical for the robustness and convergence of the flow solver.

  4. High-throughput multiple-mouse imaging with micro-PET/CT for whole-skeleton assessment

    PubMed Central

    Yagi, Masashi; Arentsen, Luke; Shanley, Ryan M; Hui, Susanta K

    2014-01-01

    Recent studies have proven that skeleton-wide functional assessment is essential to comprehensively understand physiological aspects of the skeletal system. Therefore, in contrast to regional imaging studies utilizing a multiple-animal holder (mouse hotel), we attempted to develop and characterize a multiple-mouse imaging system with micro-PET/CT for high-throughput whole-skeleton assessment. Using items found in a laboratory, a simple mouse hotel that houses four mice linked with gas anesthesia was constructed. A mouse-simulating phantom was used to measure uniformity in a cross sectional area and flatness (Amax/Amin*100) along the axial, radial and tangential directions, where Amax and Amin are maximum and minimum activity concentration in the profile, respectively. Fourteen mice were used for single- or multiple-micro-PET/CT scans. NaF uptake was measured at eight skeletal sites (skull to tibia). Skeletal 18F activities measured with mice in the mouse hotel were within 1.6±4% (mean±standard deviation) of those measured with mice in the single-mouse holder. Single-holder scanning yields slightly better uniformity and flatness over the hotel. Compared to use of the single-mouse holder, scanning with the mouse hotel reduced study time (by 65%), decreased the number of scans (four-fold), reduced cost, required less computer storage space (40%), and maximized 18F usage. The mouse hotel allows high-throughput, quantitatively equivalent scanning compared to the single-mouse holder for micro-PET/CT imaging for whole-skeleton assessment of mice. PMID:24998335

  5. Helicon waves in uniform plasmas. II. High m numbers

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    2015-09-01

    Helicons are whistler modes with azimuthal wave numbers. They have been studied in solids and plasmas where boundaries play a role. The present work shows that very similar modes exist in unbounded gaseous plasmas. Instead of boundaries, the antenna properties determine the topology of the wave packets. The simplest antenna is a magnetic loop which excites m = 0 or m = 1 helicons depending on whether the dipole moment is aligned parallel or perpendicular to the ambient background magnetic field B0. While these low order helicons have been described by J. M. Urrutia and R. L. Stenzel ["Helicon modes in uniform plasmas. I. Low m modes," Phys. Plasmas 22, 092111 (2015)], the present work focuses on high order modes up to m = 8. These are excited by antenna arrays forming magnetic multipoles. Their wave magnetic field has been measured in space and time in a large and uniform laboratory plasma free of boundary effects. The observed wave topology exhibits m pairs of unique field line spirals which may have inspired the name "helicon" to this mode. All field lines converge into these nested spirals which propagate like corkscrews along B0. The field lines near the axis of helicons are perpendicular to B0 and circularly polarized as in parallel whistlers. Helical antennas couple to these transverse fields but not to the spiral fields of helicons. Using a circular antenna array of phased m = 0 loops, right or left rotating or non-rotating multipole antenna fields are generated. They excite m < 0 and m > 0 modes, showing that the plasma supports both modes equally well. The poor excitation of m < 0 modes is a characteristic of loops with dipole moment across B0. The radiation efficiency of multipole antennas has been found to decrease with m.

  6. Helicon waves in uniform plasmas. II. High m numbers

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.

    2015-09-15

    Helicons are whistler modes with azimuthal wave numbers. They have been studied in solids and plasmas where boundaries play a role. The present work shows that very similar modes exist in unbounded gaseous plasmas. Instead of boundaries, the antenna properties determine the topology of the wave packets. The simplest antenna is a magnetic loop which excites m = 0 or m = 1 helicons depending on whether the dipole moment is aligned parallel or perpendicular to the ambient background magnetic field B{sub 0}. While these low order helicons have been described by J. M. Urrutia and R. L. Stenzel [“Helicon modes in uniform plasmas. I. Low m modes,” Phys. Plasmas 22, 092111 (2015)], the present work focuses on high order modes up to m = 8. These are excited by antenna arrays forming magnetic multipoles. Their wave magnetic field has been measured in space and time in a large and uniform laboratory plasma free of boundary effects. The observed wave topology exhibits m pairs of unique field line spirals which may have inspired the name “helicon” to this mode. All field lines converge into these nested spirals which propagate like corkscrews along B{sub 0}. The field lines near the axis of helicons are perpendicular to B{sub 0} and circularly polarized as in parallel whistlers. Helical antennas couple to these transverse fields but not to the spiral fields of helicons. Using a circular antenna array of phased m = 0 loops, right or left rotating or non-rotating multipole antenna fields are generated. They excite m < 0 and m > 0 modes, showing that the plasma supports both modes equally well. The poor excitation of m < 0 modes is a characteristic of loops with dipole moment across B{sub 0}. The radiation efficiency of multipole antennas has been found to decrease with m.

  7. Precise 3D dimensional metrology using high-resolution x-ray computed tomography (μCT)

    NASA Astrophysics Data System (ADS)

    Brunke, Oliver; Santillan, Javier; Suppes, Alexander

    2010-09-01

    Over the past decade computed tomography (CT) with conventional x-ray sources has evolved from an imaging method in medicine to a well established technology for industrial applications in fields such as material science, light metals and plastics processing, microelectronics and geology. By using modern microfocus and nanofocus X-ray tubes, parts can be scanned with sub-micrometer resolutions. Currently, micro-CT is a technology increasingly used for metrology applications in the automotive industry. CT offers big advantages compared with conventional tactile or optical coordinate measuring machines (CMMs). This is of greater importance if complex parts with hidden or difficult accessible surfaces have to be measured. In these cases, CT offers the advantage of a high density of measurement points and a non-destructive and fast capturing of the sample's complete geometry. When using this growing technology the question arises how precise a μCT based CMM can measure as compared to conventional and established methods for coordinate measurements. For characterizing the metrological capabilities of a tactile or optical CMM, internationally standardized parameters like length measurement error and probing error are defined and used. To increase the acceptance of CT as a metrological method, our work seeks to clarify the definition and usage of parameters used in the field of metrology as these apply to CT. In this paper, an overview of the process chain in CT based metrology will be given and metrological characteristics will be described. For the potential user of CT as 3D metrology tool it is important to show the measurement accuracy and repeatability on realistic samples. Following a discussion of CT metrology techniques, two samples are discussed. The first compares a measured CT Data set to CAD data using CMM data as a standard for comparison of results. The second data second realistic data set will compare the results of applying both the CMM method of

  8. The cryogenic wind tunnel concept for high Reynolds number testing

    NASA Technical Reports Server (NTRS)

    Kilgore, R. A.; Goodyer, M. J.; Adcock, J. B.; Davenport, E. E.

    1974-01-01

    Theoretical considerations indicate that cooling the wind-tunnel test gas to cryogenic temperatures will provide a large increase in Reynolds number with no increase in dynamic pressure while reducing the tunnel drive-power requirements. Studies were made to determine the expected variations of Reynolds number and other parameters over wide ranges of Mach number, pressure, and temperature, with due regard to avoiding liquefaction. Practical operational procedures were developed in a low-speed cryogenic tunnel. Aerodynamic experiments in the facility demonstrated the theoretically predicted variations in Reynolds number and drive power. The continuous-flow-fan-driven tunnel is shown to be particularly well suited to take full advantage of operating at cryogenic temperatures.

  9. Automatic tissue classification for high-resolution breast CT images based on bilateral filtering

    NASA Astrophysics Data System (ADS)

    Yang, Xiaofeng; Sechopoulos, Ioannis; Fei, Baowei

    2011-03-01

    Breast tissue classification can provide quantitative measurements of breast composition, density and tissue distribution for diagnosis and identification of high-risk patients. In this study, we present an automatic classification method to classify high-resolution dedicated breast CT images. The breast is classified into skin, fat and glandular tissue. First, we use a multiscale bilateral filter to reduce noise and at the same time keep edges on the images. As skin and glandular tissue have similar CT values in breast CT images, we use morphologic operations to get the mask of the skin based on information of its position. Second, we use a modified fuzzy C-mean classification method twice, one for the skin and the other for the fatty and glandular tissue. We compared our classified results with manually segmentation results and used Dice overlap ratios to evaluate our classification method. We also tested our method using added noise in the images. The overlap ratios for glandular tissue were above 94.7% for data from five patients. Evaluation results showed that our method is robust and accurate.

  10. High-resolution CT analysis of facial struts in trauma: 1. Normal anatomy

    SciTech Connect

    Gentry, L.R.; Manor, W.F.; Turski, P.A.; Strother, C.M.

    1983-03-01

    The recent availability of high-spatial-resolution thin-section computed tomography (CT), capable of accurately depicting the thin body septa of the facial skeleton, has expanded the role that diagnostic radiology can play in the evaluation of the patient with facial trauma. A detailed knowledge of the normal CT anatomy of the face, however, is essential to optimally utilize this modality. The normal anatomy of the face was investigated in six cadavers using thin-section (1.5 mm) high-resolution CT. A systematic method of analysis that can facilitate evaluation of the face is presented. The face is conceptualized as three groups of interconnected osseous struts or buttresses that are oriented in the horizontal, sagittal, and coronal planes. Each group of struts is closely related to specific soft-tissue structures that are susceptible to injury. Sequential evaluation of each strut and its associated soft tissue assures a comprehensive evaluation of the face. While both axial and coronal sections are of value in some circumstances, the coronal ones are most helpful in accurately depicting the structures of the face that are most likely to be injured in trauma.

  11. Development of a high-speed CT imaging system using EMCCD camera

    NASA Astrophysics Data System (ADS)

    Thacker, Samta C.; Yang, Kai; Packard, Nathan; Gaysinskiy, Valeriy; Burkett, George; Miller, Stuart; Boone, John M.; Nagarkar, Vivek

    2009-02-01

    The limitations of current CCD-based microCT X-ray imaging systems arise from two important factors. First, readout speeds are curtailed in order to minimize system read noise, which increases significantly with increasing readout rates. Second, the afterglow associated with commercial scintillator films can introduce image lag, leading to substantial artifacts in reconstructed images, especially when the detector is operated at several hundred frames/second (fps). For high speed imaging systems, high-speed readout electronics and fast scintillator films are required. This paper presents an approach to developing a high-speed CT detector based on a novel, back-thinned electron-multiplying CCD (EMCCD) coupled to various bright, high resolution, low afterglow films. The EMCCD camera, when operated in its binned mode, is capable of acquiring data at up to 300 fps with reduced imaging area. CsI:Tl,Eu and ZnSe:Te films, recently fabricated at RMD, apart from being bright, showed very good afterglow properties, favorable for high-speed imaging. Since ZnSe:Te films were brighter than CsI:Tl,Eu films, for preliminary experiments a ZnSe:Te film was coupled to an EMCCD camera at UC Davis Medical Center. A high-throughput tungsten anode X-ray generator was used, as the X-ray fluence from a mini- or micro-focus source would be insufficient to achieve high-speed imaging. A euthanized mouse held in a glass tube was rotated 360 degrees in less than 3 seconds, while radiographic images were recorded at various readout rates (up to 300 fps); images were reconstructed using a conventional Feldkamp cone-beam reconstruction algorithm. We have found that this system allows volumetric CT imaging of small animals in approximately two seconds at ~110 to 190 μm resolution, compared to several minutes at 160 μm resolution needed for the best current systems.

  12. High-resolution three-dimensional visualization of the rat spinal cord microvasculature by synchrotron radiation micro-CT

    SciTech Connect

    Hu, Jianzhong; Cao, Yong; Wu, Tianding; Li, Dongzhe; Lu, Hongbin

    2014-10-15

    Purpose: Understanding the three-dimensional (3D) morphology of the spinal cord microvasculature has been limited by the lack of an effective high-resolution imaging technique. In this study, synchrotron radiation microcomputed tomography (SRµCT), a novel imaging technique based on absorption imaging, was evaluated with regard to the detection of the 3D morphology of the rat spinal cord microvasculature. Methods: Ten Sprague-Dawley rats were used in this ex vivo study. After contrast agent perfusion, their spinal cords were isolated and scanned using conventional x-rays, conventional micro-CT (CµCT), and SRµCT. Results: Based on contrast agent perfusion, the microvasculature of the rat spinal cord was clearly visualized for the first time ex vivo in 3D by means of SRµCT scanning. Compared to conventional imaging techniques, SRµCT achieved higher resolution 3D vascular imaging, with the smallest vessel that could be distinguished approximately 7.4 μm in diameter. Additionally, a 3D pseudocolored image of the spinal cord microvasculature was generated in a single session of SRµCT imaging, which was conducive to detailed observation of the vessel morphology. Conclusions: The results of this study indicated that SRµCT scanning could provide higher resolution images of the vascular network of the spinal cord. This modality also has the potential to serve as a powerful imaging tool for the investigation of morphology changes in the 3D angioarchitecture of the neurovasculature in preclinical research.

  13. Suppression of high-density artifacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

    NASA Astrophysics Data System (ADS)

    Baissalov, Roustem; Sandison, George A.; Donnelly, Bryan J.; Saliken, John C.; Muldrew, Ken; Rewcastle, John C.

    2000-06-01

    Image guidance of cryotherapy is usually performed using ultrasound or x-ray CT. Despite the ability of CT to display the full 3D structure of the iceball, including frozen and unfrozen regions, the quality of the images is compromised by the presence of high density streak artifacts. To suppress these artifacts we applied Temporal Digital Subtraction (TDS). This TDS method has the added advantage of improving the gray scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high density artifacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced content of the artifacts. This TDS can be used in x-ray CT assisted cryotherapy to significantly suppress or eliminate high density x-ray CT streak artifacts by digitally processing x-ray CT images. Applying TDS in cryotherapy will facilitate estimation of the amount and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

  14. High Reynolds number effects on a localized stratified turbulent flow

    NASA Astrophysics Data System (ADS)

    Zhou, Qi; Diamessis, Peter

    2015-11-01

    We report large-eddy simulations (LES) of the turbulent flow behind a sphere of diameter D translating at speed U in a linearly stratified Boussinesq fluid with buoyancy frequency N. These simulations are performed using a spectral-multidomain-penalty incompressible Navier-Stokes solver, at Reynolds numbers Re ≡ UD / ν ∈ { 5 ×103 , 105 , 4 ×105 } and Froude numbers Fr ≡ 2 U / (ND) ∈ { 4 , 16 , 64 } . An increasingly richer turbulent fine-structure is observed within the larger-scale quasi-horizontal vortices at later times. Turbulent transport of momentum is examined during the non-equilibrium (NEQ) regime of the turbulent life cycle, with an emphasis on the vertical transport that occurs after the establishment of local buoyancy control. The turbulent viscosities in both horizontal and vertical directions are estimated through the LES data; possible parameterization of the vertical turbulent viscosity with the buoyancy Reynolds number Reb = ɛ / (νN2) (or its easy-to-obtain surrogates) is discussed. The dynamical role of the buoyancy Reynolds number in choosing the vertical turbulence length scales is also investigated. ONR grant N00014-13-1-0665 (managed by Dr. R. Joslin); HPCMP Frontier Project FP-CFD-FY14-007 (P.I.: Dr. S. de Bruyn Kops).

  15. Prediction of Very High Reynolds Number Compressible Skin Friction

    NASA Technical Reports Server (NTRS)

    Carlson, John R.

    1998-01-01

    Flat plate skin friction calculations over a range of Mach numbers from 0.4 to 3.5 at Reynolds numbers from 16 million to 492 million using a Navier Stokes method with advanced turbulence modeling are compared with incompressible skin friction coefficient correlations. The semi-empirical correlation theories of van Driest; Cope; Winkler and Cha; and Sommer and Short T' are used to transform the predicted skin friction coefficients of solutions using two algebraic Reynolds stress turbulence models in the Navier-Stokes method PAB3D. In general, the predicted skin friction coefficients scaled well with each reference temperature theory though, overall the theory by Sommer and Short appeared to best collapse the predicted coefficients. At the lower Reynolds number 3 to 30 million, both the Girimaji and Shih, Zhu and Lumley turbulence models predicted skin-friction coefficients within 2% of the semi-empirical correlation skin friction coefficients. At the higher Reynolds numbers of 100 to 500 million, the turbulence models by Shih, Zhu and Lumley and Girimaji predicted coefficients that were 6% less and 10% greater, respectively, than the semi-empirical coefficients.

  16. Numerical simulations of thermal convection at high Prandtl numbers

    NASA Astrophysics Data System (ADS)

    Silano, Gabriella

    2008-11-01

    Direct numerical simulations of thermal convection are conducted for a cylindrical cell of aspect ratio .5ex1-.1em/ -.15em.25ex2 . The Prandtl number (Pr) varies from 10^0 to 10^4 and the Rayleigh numbers (Ra) are moderate (10^5 < Ra < 10^9). This study is motivated by the fact that the role of the Prandtl number in convective heat transport is not yet fully understood. The three-dimensional behaviors of the temperature and velocity fields, of the viscous and thermal dissipation fields, and of the diffusive and convective heat fluxes are explored. In the ranges of Pr and Ra considered, we find steady, periodic and chaotic regimes, and large-scale structures which are more complex than the single recirculation cell filling the whole volume. Multiple flow structures are found to be associated with a given set of conditions. The multiple solutions seem to be more probable at higher Pr numbers and could explain the scatter in some data trends. In collaboration with Katepalli Raju Sreenivasan, The Abdus Salam International Centre for Theoretical Physics - Trieste, and Roberto Verzicco, DIM, Universitàdegli Studi di Roma Tor Vergata - Roma.

  17. Spectral deblurring: an algorithm for high-resolution, hybrid spectral CT

    NASA Astrophysics Data System (ADS)

    Clark, D. P.; Badea, C. T.

    2015-03-01

    We are developing a hybrid, dual-source micro-CT system based on the combined use of an energy integrating (EID) x-ray detector and a photon counting x-ray detector (PCXD). Due to their superior spectral resolving power, PCXDs have the potential to reduce radiation dose and to enable functional and molecular imaging with CT. In most current PCXDs, however, spatial resolution and field of view are limited by hardware development and charge sharing effects. To address these problems, we propose spectral deblurring—a relatively simple algorithm for increasing the spatial resolution of hybrid, spectral CT data. At the heart of the algorithm is the assumption that the underlying CT data is piecewise constant, enabling robust recovery in the presence of noise and spatial blur by enforcing gradient sparsity. After describing the proposed algorithm, we summarize simulation experiments which assess the trade-offs between spatial resolution, contrast, and material decomposition accuracy given realistic levels of noise. When the spatial resolution between imaging chains has a ratio of 5:1, spectral deblurring results in a 52% increase in the material decomposition accuracy of iodine, gadolinium, barium, and water vs. linear interpolation. For a ratio of 10:1, a realistic representation of our hybrid imaging system, a 52% improvement was also seen. Overall, we conclude that the performance breaks down around high frequency and low contrast structures. Following the simulation experiments, we apply the algorithm to ex vivo data acquired in a mouse injected with an iodinated contrast agent and surrounded by vials of iodine, gadolinium, barium, and water.

  18. High density resolution synchrotron radiation based x-ray microtomography (SR μCT) for quantitative 3D-morphometrics in zoological sciences

    NASA Astrophysics Data System (ADS)

    Nickel, Michael; Hammel, Jörg U.; Herzen, Julia; Bullinger, Eric; Beckmann, Felix

    2008-08-01

    Zoological sciences widely rely on morphological data to reconstruct and understand body structures of animals. The best suitable methods like tomography allow for a direct representation of 3D-structures. In recent years, synchrotron radiation based x-ray microtomography (SR μCT) placed high resolutions to the disposal of morphologists. With the development of highly brilliant and collimated third generation synchrotron sources, phase contrast SR μCT became widely available. A number of scientific contributions stressed the superiority of phase contrast over absorption contrast. However, here we demonstrate the power of high density resolution methods based on absorption-contrast SRμCT for quantitative 3D-measurements of tissues and other delicate bio-structures in zoological sciences. We used beamline BW2 at DORIS III (DESY, Hamburg, Germany) to perform microtomography on tissue and mineral skeletons of marine sponges (Porifera) which were shock frozen and/or fixed in a glutamate osmium tetroxide solution, followed by critical point drying. High density resolution tomographic reconstructions allowed running quantitative 3D-image analyses in Matlab and ImageJ. By applying contrast and shape rule based algorithms we semi-automatically extracted and measured sponge body structures like mineral spicules, elements of the canal system or tissue structures. This lead to a better understanding of sponge biology: from skeleton functional morphology and internal water flow regimes to body contractility. Our high density resolution based quantitative approach can be applied to a wide variety of biological structures. However, two prerequisites apply: (1) maximum density resolution is necessary; (2) edge effects as seen for example in phase outline contrast SR μCT must not be present. As a consequence, to allow biological sciences to fully exploit the power of SR μCT further increase of density resolution in absorption contrast methods is desirable.

  19. High Reynolds Number Configuration Development of a High-Lift Airfoil

    NASA Technical Reports Server (NTRS)

    Valarezo, Walter O.; Dominik, Chet J.; Mcghee, Robert J.; Goodman, Wesley L.

    1993-01-01

    An experimental program has been conducted to assess performance of a transport multielement airfoil at flight Reynolds numbers. The studies were performed at chord Reynolds numbers as high as 16 million in the NASA Langley Low Turbulence Pressure Tunnel. Sidewall boundary-layer control to enforce flow two dimensionality was provided via an endplate suction system. The basic airfoil was an 11.55 percent thick supercritical airfoil representative of the stall critical station of a new-generation transport aircraft wing. The multielement airfoil was configured as a three-element airfoil with slat and flap chord ratios of 14.48 percent and 30 percent respectively. Testing focused on the development of landing configurations with high maximum lift capability and the assessment of Reynolds and Mach number effects. Also assessed were high-lift performance effects due to devices such as drooped spoilers and trailing-edge wedges. The present experimental studies revealed significant effects on high-lift airfoil performance due to Reynolds and Mach number variations and favorable lift increments at approach angles of attack due to the use of drooped spoilers or trailing-edge wedges. However, no substantial improvements in maximum lift capability were identified. A recently developed high performance single-segment flap was also tested and results indicated considerable improvements in lift and drag performance over existing airfoils. Additionally, it was found that this new flap shape at its optimum rigging was less sensitive to Reynolds number variations than previous designs.

  20. Numerical study of high frequency oscillatory air flow and convective mixing in a CT-based human airway model

    PubMed Central

    Choi, Jiwoong; Xia, Guohua; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long

    2011-01-01

    High frequency oscillatory ventilation (HFOV) is considered an efficient and safe respiratory technique to ventilate neonates and patients with acute respiratory distress syndrome. HFOV has very different characteristics from normal breathing physiology, with a much smaller tidal volume and a higher breathing frequency. In this work, the high frequency oscillatory flow is studied using a computational fluid dynamics (CFD) analysis in three different geometrical models with increasing complexity: a straight tube, a single-bifurcation tube model, and a computed-tomography (CT)-based human airway model of up to seven generations. We aim to understand the counter-flow phenomenon at flow reversal and its role in convective mixing in these models using sinusoidal waveforms of different frequencies and Reynolds numbers. Mixing is quantified by the stretch rate analysis. In the straight-tube model, coaxial counter flow with opposing fluid streams is formed around flow reversal, agreeing with an analytical Womersley solution. However, counter flow yields no net convective mixing at end cycle. In the single-bifurcation model, counter flow at high Re is intervened with secondary vortices in the parent (child) branch at end expiration (inspiration), resulting in an irreversible mixing process. For the CT-based airway model three cases are considered, consisting of the normal breathing case, the high-frequency-normal-Re case, and the HFOV case. The counter-flow structure is more evident in the high-frequency-normal-Re case than the HFOV case. The instantaneous and time-averaged stretch rates at the end of two breathing cycles and in the vicinity of flow reversal are computed. It is found that counter flow contributes about 20% to mixing in HFOV. PMID:20614248

  1. Nonalcoholic Hepatic Steatosis Is a Strong Predictor of High-Risk Coronary-Artery Plaques as Determined by Multidetector CT

    PubMed Central

    Osawa, Kazuhiro; Miyoshi, Toru; Yamauchi, Kentarou; Koyama, Yasushi; Nakamura, Kazufumi; Sato, Shuhei; Kanazawa, Susumu; Ito, Hiroshi

    2015-01-01

    Background Nonalcoholic fatty liver disease is associated with a risk of coronary artery disease (e.g., diabetes mellitus, dyslipidemia, metabolic syndrome). We evaluated whether nonalcoholic hepatic steatosis is associated with high-risk plaques as assessed by multidetector computed tomography (CT). Methods This retrospective study involved 414 participants suspected of having coronary artery disease. Nonalcoholic hepatic steatosis was defined as a liver-to-spleen fat ratio of <1.0 and the presence and appropriate characteristics of coronary-artery plaques as assessed by coronary CT angiography. High-risk plaques were identified, as were low-density plaques, positive remodeling, and spotty calcification. Results Compared with patients who did not have nonalcoholic hepatic steatosis, patients with nonalcoholic hepatic steatosis had more low-density plaques (21% vs. 44%, p<0.01), positive remodeling (41% vs. 58%, p = 0.01), and spotty calcification (12% vs. 36%, p<0.01). The number of high-risk plaques in patients with nonalcoholic hepatic steatosis was greater than in those without nonalcoholic hepatic steatosis (p<0.01). Patients with nonalcoholic hepatic steatosis were more likely to have high-risk plaques than were those with only an elevated level of visceral adipose tissue (≥86 cm2; 35% vs. 16%, p<0.01). Multivariate analyses that included nonalcoholic hepatic steatosis, amount of visceral adipose tissue, and the presence/absence of traditional risk factors demonstrated that nonalcoholic hepatic steatosis was an independent predictor of high-risk plaques (odds ratio: 4.60; 95% confidence interval: 1.94–9.07, p<0.01). Conclusions Diagnosis of nonalcoholic hepatic steatosis may be of value when assessing the risk of coronary artery disease. PMID:26125952

  2. Multiplier less high-speed squaring circuit for binary numbers

    NASA Astrophysics Data System (ADS)

    Sethi, Kabiraj; Panda, Rutuparna

    2015-03-01

    The squaring operation is important in many applications in signal processing, cryptography etc. In general, squaring circuits reported in the literature use fast multipliers. A novel idea of a squaring circuit without using multipliers is proposed in this paper. Ancient Indian method used for squaring decimal numbers is extended here for binary numbers. The key to our success is that no multiplier is used. Instead, one squaring circuit is used. The hardware architecture of the proposed squaring circuit is presented. The design is coded in VHDL and synthesised and simulated in Xilinx ISE Design Suite 10.1 (Xilinx Inc., San Jose, CA, USA). It is implemented in Xilinx Vertex 4vls15sf363-12 device (Xilinx Inc.). The results in terms of time delay and area is compared with both modified Booth's algorithm and squaring circuit using Vedic multipliers. Our proposed squaring circuit seems to have better performance in terms of both speed and area.

  3. The riddle of high-energy baryon number violation

    SciTech Connect

    Mattis, M.P.

    1991-09-01

    The exciting possibility that anomalous baryon and lepton number violation might be observable at the next generation of supercolliders is suggested by an instanton calculation due to Ringwald and Espinosa. In these Lectures, the current controversial status of these claims is discussed, and several new technologies designed to analyze this question are reviewed. These technologies should contribute more generally to our understanding of weakly- coupled field theories in the nonperturbative regime where both energies and multiplicities are very large. 61 refs., 35 figs.

  4. Grid-generated isotropic homogeneous turbulence at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Rosen, G.

    1981-01-01

    Consideration is given to an empirical formula for the longitudinal correlation function for grid-generated incompressible fluid turbulence at Reynolds numbers above 12,800. The formula, which relates the longitudinal correlation function to the inverse cube of a dimensionless geometrical ratio, is shown to minimize the global correlation integrals into which the two-point velocity correlation tensor has been substituted subject to a global constraint on the Sobolev concomitent of the longitudinal correlation function. Furthermore, the energy spectrum function associated with the empirical formula is shown to satisfy a tertiary Helmholtz-type linear condition throughout the initial period of decay.

  5. Numerical study of high-frequency oscillatory air flow and convective mixing in a CT-based human airway model.

    PubMed

    Choi, Jiwoong; Xia, Guohua; Tawhai, Merryn H; Hoffman, Eric A; Lin, Ching-Long

    2010-12-01

    High-frequency oscillatory ventilation (HFOV) is considered an efficient and safe respiratory technique to ventilate neonates and patients with acute respiratory distress syndrome. HFOV has very different characteristics from normal breathing physiology, with a much smaller tidal volume and a higher breathing frequency. In this study, the high-frequency oscillatory flow is studied using a computational fluid dynamics analysis in three different geometrical models with increasing complexity: a straight tube, a single-bifurcation tube model, and a computed tomography (CT)-based human airway model of up to seven generations. We aim to understand the counter-flow phenomenon at flow reversal and its role in convective mixing in these models using sinusoidal waveforms of different frequencies and Reynolds (Re) numbers. Mixing is quantified by the stretch rate analysis. In the straight-tube model, coaxial counter flow with opposing fluid streams is formed around flow reversal, agreeing with an analytical Womersley solution. However, counter flow yields no net convective mixing at end cycle. In the single-bifurcation model, counter flow at high Re is intervened with secondary vortices in the parent (child) branch at end expiration (inspiration), resulting in an irreversible mixing process. For the CT-based airway model three cases are considered, consisting of the normal breathing case, the high-frequency-normal-Re (HFNR) case, and the HFOV case. The counter-flow structure is more evident in the HFNR case than the HFOV case. The instantaneous and time-averaged stretch rates at the end of two breathing cycles and in the vicinity of flow reversal are computed. It is found that counter flow contributes about 20% to mixing in HFOV. PMID:20614248

  6. Turbulent Boundary Layer in High Rayleigh Number Convection in Air

    NASA Astrophysics Data System (ADS)

    du Puits, Ronald; Li, Ling; Resagk, Christian; Thess, André; Willert, Christian

    2014-03-01

    Flow visualizations and particle image velocimetry measurements in the boundary layer of a Rayleigh-Bénard experiment are presented for the Rayleigh number Ra =1.4×1010. Our visualizations indicate that the appearance of the flow structures is similar to ordinary (isothermal) turbulent boundary layers. Our particle image velocimetry measurements show that vorticity with both positive and negative sign is generated and that the smallest flow structures are 1 order of magnitude smaller than the boundary layer thickness. Additional local measurements using laser Doppler velocimetry yield turbulence intensities up to I=0.4 as in turbulent atmospheric boundary layers. From our observations, we conclude that the convective boundary layer becomes turbulent locally and temporarily although its Reynolds number Re ≈200 is considerably smaller than the value 420 underlying existing phenomenological theories. We think that, in turbulent Rayleigh-Bénard convection, the transition of the boundary layer towards turbulence depends on subtle details of the flow field and is therefore not universal.

  7. Design of a High-Reynolds Number Recirculating Water Tunnel

    NASA Astrophysics Data System (ADS)

    Daniel, Libin; Elbing, Brian

    2014-11-01

    An experimental fluid mechanics laboratory focused on turbulent boundary layers, drag reduction techniques, multiphase flows and fluid-structure interactions has recently been established at Oklahoma State University. This laboratory has three primary components; (1) a recirculating water tunnel, (2) a multiphase pipe flow loop, and (3) a multi-scale flow visualization system. The design of the water tunnel is the focus of this talk. The criteria used for the water tunnel design was that it had to produce a momentum-thickness based Reynolds number in excess of 104, negligible flow acceleration due to boundary layer growth, maximize optical access for use of the flow visualization system, and minimize inlet flow non-uniformity. This Reynolds number was targeted to bridge the gap between typical university/commercial water tunnels (103) and the world's largest water tunnel facilities (105) . These objectives were achieved with a 152 mm (6-inch) square test section that is 1 m long and has a maximum flow speed of 10 m/s. The flow non-uniformity was mitigated with the use of a tandem honeycomb configuration, a settling chamber and an 8.5:1 contraction. The design process that produced this final design will be presented along with its current status.

  8. High-Reynolds Number Taylor-Couette Turbulence

    NASA Astrophysics Data System (ADS)

    Grossmann, Siegfried; Lohse, Detlef; Sun, Chao

    2016-01-01

    Taylor-Couette flow, the flow between two coaxial co- or counter-rotating cylinders, is one of the paradigmatic systems in the physics of fluids. The (dimensionless) control parameters are the Reynolds numbers of the inner and outer cylinders, the ratio of the cylinder radii, and the aspect ratio. One key response of the system is the torque required to retain constant angular velocities, which can be connected to the angular velocity transport through the gap. Whereas the low-Reynolds number regime was well explored in the 1980s and 1990s of the past century, in the fully turbulent regime major research activity developed only in the past decade. In this article, we review this recent progress in our understanding of fully developed Taylor-Couette turbulence from the experimental, numerical, and theoretical points of view. We focus on the parameter dependence of the global torque and on the local flow organization, including velocity profiles and boundary layers. Next, we discuss transitions between different (turbulent) flow states. We also elaborate on the relevance of this system for astrophysical disks (quasi-Keplerian flows). The review ends with a list of challenges for future research on turbulent Taylor-Couette flow.

  9. Aeroacoustic Data for a High Reynolds Number Axisymmetric Subsonic Jet

    NASA Technical Reports Server (NTRS)

    Ponton, Michael K.; Ukeiley, Lawrence S.; Lee, Sang W.

    1999-01-01

    The near field fluctuating pressure and aerodynamic mean flow characteristics of a cold subsonic jet issuing from a contoured convergent nozzle are presented. The data are presented for nozzle exit Mach numbers of 0.30, 0.60, and 0.85 at a constant jet stagnation temperature of 104 F. The fluctuating pressure measurements were acquired via linear and semi-circular microphone arrays and the presented results include plots of narrowband spectra, contour maps, streamwise/azimuthal spatial correlations for zero time delay, and cross-spectra of the azimuthal correlations. A pitot probe was used to characterize the mean flow velocity by assuming the subsonic flow to be pressure-balanced with the ambient field into which it exhausts. Presented are mean flow profiles and the momentum thickness of the free shear layer as a function of streamwise position.

  10. Convection in an ideal gas at high Rayleigh numbers.

    PubMed

    Tilgner, A

    2011-08-01

    Numerical simulations of convection in a layer filled with ideal gas are presented. The control parameters are chosen such that there is a significant variation of density of the gas in going from the bottom to the top of the layer. The relations between the Rayleigh, Peclet, and Nusselt numbers depend on the density stratification. It is proposed to use a data reduction which accounts for the variable density by introducing into the scaling laws an effective density. The relevant density is the geometric mean of the maximum and minimum densities in the layer. A good fit to the data is then obtained with power laws with the same exponent as for fluids in the Boussinesq limit. Two relations connect the top and bottom boundary layers: The kinetic energy densities computed from free fall velocities are equal at the top and bottom, and the products of free fall velocities and maximum horizontal velocities are equal for both boundaries. PMID:21929106

  11. Numerical simulation of high Reynolds number bubble motion

    SciTech Connect

    McLaughlin, J.B.

    1995-12-31

    This paper presents the results of numerical simulations of bubble motion. All the results are for single bubbles in unbounded fluids. The liquid phase is quiescent except for the motion created by the bubble, which is axisymmetric. The main focus of the paper is on bubbles that are of order 1 mm in diameter in water. Of particular interest is the effect of surfactant molecules on bubble motion. Results for the {open_quotes}insoluble surfactant{close_quotes} model will be presented. These results extend research by other investigators to finite Reynolds numbers. The results indicate that, by assuming complete coverage of the bubble surface, one obtains good agreement with experimental observations of bubble motion in tap water. The effect of surfactant concentration on the separation angle is discussed.

  12. High Rayleigh number simulations in a slender laterally periodic domain

    NASA Astrophysics Data System (ADS)

    Verzicco, Roberto; van der Poel, Erwin; Lohse, Detlef

    2015-11-01

    The results of three-dimensional DNS simulations of Rayleigh-Bénard convection with Ra up to 1013 in a laterally periodic geometry with progressively decreasing aspect-ratios are presented. We show global quantities such as the heat transport as well as local time-averages and vertical profiles. It is observed that the heat transport for laterally unconfined geometries can be computed at relatively small aspect-ratios whose value decreases with Rayleigh number. This is beneficial in terms of computational cost, as the total simulated domain gets smaller. The boundary layers profiles are studied and movies of horizontal cross-section of the bulk and the boundary layer are shown.

  13. Parametric Investigation of a High-Lift Airfoil at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Lin, John C.; Dominik, Chet J.

    1997-01-01

    A new two-dimensional, three-element, advanced high-lift research airfoil has been tested in the NASA Langley Research Center s Low-Turbulence Pressure Tunnel at a chord Reynolds number up to 1.6 x 107. The components of this high-lift airfoil have been designed using a incompressible computational code (INS2D). The design was to provide high maximum-lift values while maintaining attached flow on the single-segment flap at landing conditions. The performance of the new NASA research airfoil is compared to a similar reference high-lift airfoil. On the new high-lift airfoil the effects of Reynolds number on slat and flap rigging have been studied experimentally, as well as the Mach number effects. The performance trend of the high-lift design is comparable to that predicted by INS2D over much of the angle-of-attack range. However, the code did not accurately predict the airfoil performance or the configuration-based trends near maximum lift where the compressibility effect could play a major role.

  14. Elastic turbulence in high Reynolds number polymer drag reduced flows

    NASA Astrophysics Data System (ADS)

    Dubief, Yves; White, Christopher

    2011-11-01

    The present study discusses the existence of small scale dynamics resembling elastic turbulence in polymeric transitional and maximum drag reduction (MDR) flows. The observed flow patterns are driven by elastic stress and occur in regions of very low turbulence found before and after the breakdown of nonlinear instabilities in polymeric transitional flows leading to MDR. A state of polymer-dominated spanwise instabilities was found, resulting in a structure of the wall shear quite different than the structures observed in transitional Newtonian flow. Similar instabilities are observed in the wake of the head of hairpin vortices in simulated MDR flows, an extended region of extensional flow of the order of the Kolmogorov scale in the normal direction. The important Reynolds number is not that of flow (Reτ = 300 and 600 for the Newtonian flows) but that of the local turbulent flow, which according to Kolmogorov approaches unity in the above mentioned flows, a reasonable magnitude for elastic turbulence. The existence of small scale elastic turbulence in transitional and MDR flows explains the phenomenon of early turbulence first observed in the 70s and challenges the notion that, in drag reduced flows, the energy flows only from large to small scales and never goes back from polymers to flow.

  15. Hodograph design of lifting airfoils with high critical mach numbers

    NASA Astrophysics Data System (ADS)

    Kropinski, M. C. A.; Schwendeman, D. W.; Cole, J. D.

    1995-05-01

    We wish to construct airfoils that have the highest free-stream Mach number M ∞ for a given set of geometric constraints for which the flow is nowhere supersonic. Nonlifting airfoils which maximize M ∞ for a given thickness ratio δ are known to possess long sonic segments at their critical speed. To construct lifting airfoils, we proceed under the conjecture that the optimal airfoil satisfying a given set of constraints is the one possessing the longest possible arc length of sonic velocity. A boundary-value problem is formulated in the hodograph plane using transonic small-disturbance theory whose solution determines an airfoil with long sonic arcs. For small lift coefficients, the hodograph domain covers two Riemann sheets and a finite-difference method is used to solve the boundary-value problem on this domain. A numerical integration of the solution around the boundary yields an airfoil shape, and three examples are discussed. The performance of these airfoils is compared with standard airfoils having the same lift coefficient and δ, and it is shown that the calculated airfoils have a 6% 10% increase in critical M ∞.

  16. Promising electron mobility and high thermal conductivity in Sc2CT2 (T = F, OH) MXenes.

    PubMed

    Zha, Xian-Hu; Zhou, Jie; Zhou, Yuhong; Huang, Qing; He, Jian; Francisco, Joseph S; Luo, Kan; Du, Shiyu

    2016-03-10

    MXenes, the new 2D transition metal carbides and nitrides, have recently attracted extensive attention due to their diverse applications and excellent performances. However, the thermal and electrical properties of most MXene materials are yet to be studied. In this work, we investigate the electrical and thermal properties of semiconducting Sc2CT2 (T = F, OH) MXenes using first-principles calculations. Both of the Sc2CT2 (T = F, OH) MXenes are determined to show excellent carrier mobilities. The electron mobility in the Sc2CF2 MXene is found to be strongly anisotropic at room temperature, with values of 5.03 × 10(3) and 1.07 × 10(3) cm(2) V(-1) s(-1) in the zigzag and armchair directions, respectively. The predicted electron mobility in the zigzag direction of the Sc2CF2 is nearly four-fold that in the armchair direction of the promising semiconductor phosphorene. In contrast to Sc2CF2, Sc2C(OH)2 presents approximately isotropic electron mobility. The values at room temperature in the zigzag and armchair directions are calculated as 2.06 × 10(3) cm(2) V(-1) s(-1) and 2.19 × 10(3) cm(2) V(-1) s(-1), respectively. In regard to the thermal properties, the thermal conductivities of the Sc2CT2 (T = F, OH) MXenes have been determined. The predicted values are higher than those of most metals and semiconducting low-dimensional materials, such as monolayer MoS2 and phosphorene. In particular, the room-temperature thermal conductivity along the Sc2CF2 armchair direction has been determined to be as high as 472 W m(-1) K(-1) based on a flake length of 5 μm, which is even higher than that of the best traditional conductor silver. The corresponding value in the zigzag direction of Sc2CF2 is calculated to be 178 W m(-1) K(-1). The thermal conductivity in Sc2C(OH)2 is less anisotropic and lower compared to that in Sc2CF2. The room-temperature value in the armchair (zigzag) direction is determined to be 173 W m(-1) K(-1) (107 W m(-1) K(-1)). Based on their excellent

  17. Normalizations of High Taylor Reynolds Number Power Spectra

    NASA Astrophysics Data System (ADS)

    Puga, Alejandro; Koster, Timothy; Larue, John C.

    2014-11-01

    The velocity power spectrum provides insight in how the turbulent kinetic energy is transferred from larger to smaller scales. Wind tunnel experiments are conducted where high intensity turbulence is generated by means of an active turbulence grid modeled after Makita's 1991 design (Makita, 1991) as implemented by Mydlarski and Warhaft (M&W, 1998). The goal of this study is to document the evolution of the scaling region and assess the relative collapse of several proposed normalizations over a range of Rλ from 185 to 997. As predicted by Kolmogorov (1963), an asymptotic approach of the slope (n) of the inertial subrange to - 5 / 3 with increasing Rλ is observed. There are three velocity power spectrum normalizations as presented by Kolmogorov (1963), Von Karman and Howarth (1938) and George (1992). Results show that the Von Karman and Howarth normalization does not collapse the velocity power spectrum as well as the Kolmogorov and George normalizations. The Kolmogorov normalization does a good job of collapsing the velocity power spectrum in the normalized high wavenumber range of 0 . 0002 <= κλ <= 0 . 4 while the George normalization does a better job in the normalized mid-wavenumber range of 15 <= κλ <= 25 . University of California, Irvine Research Fund.

  18. Promising electron mobility and high thermal conductivity in Sc2CT2 (T = F, OH) MXenes

    NASA Astrophysics Data System (ADS)

    Zha, Xian-Hu; Zhou, Jie; Zhou, Yuhong; Huang, Qing; He, Jian; Francisco, Joseph S.; Luo, Kan; Du, Shiyu

    2016-03-01

    MXenes, the new 2D transition metal carbides and nitrides, have recently attracted extensive attention due to their diverse applications and excellent performances. However, the thermal and electrical properties of most MXene materials are yet to be studied. In this work, we investigate the electrical and thermal properties of semiconducting Sc2CT2 (T = F, OH) MXenes using first-principles calculations. Both of the Sc2CT2 (T = F, OH) MXenes are determined to show excellent carrier mobilities. The electron mobility in the Sc2CF2 MXene is found to be strongly anisotropic at room temperature, with values of 5.03 × 103 and 1.07 × 103 cm2 V-1 s-1 in the zigzag and armchair directions, respectively. The predicted electron mobility in the zigzag direction of the Sc2CF2 is nearly four-fold that in the armchair direction of the promising semiconductor phosphorene. In contrast to Sc2CF2, Sc2C(OH)2 presents approximately isotropic electron mobility. The values at room temperature in the zigzag and armchair directions are calculated as 2.06 × 103 cm2 V-1 s-1 and 2.19 × 103 cm2 V-1 s-1, respectively. In regard to the thermal properties, the thermal conductivities of the Sc2CT2 (T = F, OH) MXenes have been determined. The predicted values are higher than those of most metals and semiconducting low-dimensional materials, such as monolayer MoS2 and phosphorene. In particular, the room-temperature thermal conductivity along the Sc2CF2 armchair direction has been determined to be as high as 472 W m-1 K-1 based on a flake length of 5 μm, which is even higher than that of the best traditional conductor silver. The corresponding value in the zigzag direction of Sc2CF2 is calculated to be 178 W m-1 K-1. The thermal conductivity in Sc2C(OH)2 is less anisotropic and lower compared to that in Sc2CF2. The room-temperature value in the armchair (zigzag) direction is determined to be 173 W m-1 K-1 (107 W m-1 K-1). Based on their excellent electron mobilities and high thermal

  19. High-resolution 3D micro-CT imaging of breast microcalcifications: a preliminary analysis

    PubMed Central

    2014-01-01

    Background Detection of microcalcifications on mammograms indicates the presence of breast lesion, and the shapes of the microcalcifications as seen by conventional mammography correlates with the probability of malignancy. This preliminary study evaluated the 3D shape of breast microcalcifications using micro-computed tomography (micro-CT) and compared the findings with those obtained using anatomopathological analysis. Methods The study analyzed breast biopsy samples from 11 women with findings of suspicious microcalcifications on routine mammograms. The samples were imaged using a micro-CT (SkyScan 1076) at a resolution of 35 μm. Images were reconstructed using filtered back-projection and analyzed in 3D using surface rendering. The samples were subsequently analyzed by the pathology service. Reconstructed 3D images were compared with the corresponding histological slices. Results Anatomopathological analysis showed that 5 of 11 patients had ductal breast carcinoma in situ. One patient was diagnosed with invasive ductal carcinoma. Individual object analysis was performed on 597 microcalcifications. Malignant microcalcifications tended to be thinner and to have a smaller volume and surface area, while their surface area-to-volume ratio was greater than that of benign microcalcifications. The structure model index values were the same for malignant and benign microcalcifications. Conclusions This is the first study to use micro-CT for quantitative 3D analysis of microcalcifications. This high-resolution imaging technique will be valuable for gaining a greater understanding of the morphologic characteristics of malignant and benign microcalcifications. The presence of many small microcalcifications can be an indication of malignancy. For the larger microcalcifications, 3D parameters confirmed the more irregular shape of malignant microcalcifications. PMID:24393444

  20. High-resolution CT analysis of facial struts in trauma: 1. Osseous and soft-tissue complications

    SciTech Connect

    Gentry, L.R.; Manor, W.F.; Turski, P.A.; Strother, C.M.

    1983-03-01

    In six cadavers, high-resolution thin-section computed tomography (CT) was used to evaluate the sequelae of experimentally produced facial trauma. As confirmed by pluridirectional tomography, CT was an effective imaging method for the detection and classification of facial fractures. The ability of CT to simultaneously depict both osseous and soft-tissue structures expands the role that diagnostic radiology can play in the evaluation of the traumatized face. A method of evaluation is presented in which the face is geometrically conceptualized as a series of triplanar (horizontal, sagittal, and coronal) osseous struts. Sequential, systematic assessment of each strut for fracture and its adjacent soft tissue for injury can facilitate evaluation of the traumatized face. Using this approach the osseous and soft-tissue complications arising from experimentally produced trauma are reviewed and illustrated with CT.

  1. Rayleigh Taylor instability of viscoelastic drops at high Weber numbers

    NASA Astrophysics Data System (ADS)

    Joseph, D. D.; Beavers, G. S.; Funada, T.

    2002-02-01

    Movies of the breakup of viscous and viscoelastic drops in the high-speed airstream behind a shock wave in a shock tube have been reported by Joseph, Belanger & Beavers (1999). They performed a Rayleigh Taylor stability analysis for the initial breakup of a drop of Newtonian liquid and found that the most unstable Rayleigh Taylor wave fits nearly perfectly with waves measured on enhanced images of drops from the movies, but the effects of viscosity cannot be neglected. Here we construct a Rayleigh Taylor stability analysis for an Oldroyd-B fluid using measured data for acceleration, density, viscosity and relaxation time [lambda]1. The most unstable wave is a sensitive function of the retardation time [lambda]2 which fits experiments when [lambda]2/[lambda]1 = O(10-3). The growth rates for the most unstable wave are much larger than for the comparable viscous drop, which agrees with the surprising fact that the breakup times for viscoelastic drops are shorter. We construct an approximate analysis of Rayleigh Taylor instability based on viscoelastic potential flow which gives rise to nearly the same dispersion relation as the unapproximated analysis.

  2. A survey of the three-dimensional high Reynolds number transonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Takashima, K.; Sawada, H.; Aoki, T.

    1982-01-01

    The facilities for aerodynamic testing of airplane models at transonic speeds and high Reynolds numbers are surveyed. The need for high Reynolds number testing is reviewed, using some experimental results. Some approaches to high Reynolds number testing such as the cryogenic wind tunnel, the induction driven wind tunnel, the Ludwieg tube, the Evans clean tunnel and the hydraulic driven wind tunnel are described. The level of development of high Reynolds number testing facilities in Japan is discussed.

  3. Auditory profile and high resolution CT scan in autism spectrum disorders children with auditory hypersensitivity.

    PubMed

    Thabet, Elsaeid M; Zaghloul, Hesham S

    2013-08-01

    Autism is the third most common developmental disorder, following mental retardationand cerebral palsy. ASD children have been described more often as beingpreoccupied with or agitated by noise. The aim of this study was to evaluate theprevalence and clinical significance of semicircular canal dehiscence detected on CTimages in ASD children with intolerance to loud sounds in an attempt to find ananatomical correlate with hyperacusis.14 ASD children with auditory hypersensitivity and 15 ASD children without auditoryhypersensitivity as control group age and gender matched were submitted to historytaking, otological examination, tympanometry and acoustic reflex thresholdmeasurement. ABR was done to validate normal peripheral hearing and integrity ofauditory brain stem pathway. High resolution CT scan petrous and temporal boneimaging was performed to all participated children. All participants had normal hearingsensitivity in ABR testing. Absolute ABR peak waves of I and III showed no statisticallysignificant difference between the two groups, while absolute wave V peak andinterpeak latencies I-V and III-V were shorter in duration in study group whencompared to the control group. CT scans revealed SSCD in 4 out of 14 of the studygroup (29%), the dehiscence was bilateral in one patient and unilateral in threepatients. None of control group showed SSCD. In conclusion, we have reportedevidence that apparent hypersensitivity to auditory stimuli (short conduction time in ABR) despite the normal physiological measures in ASD children with auditoryhypersensitivity can provide a clinical clue of a possible SSCD. PMID:23580033

  4. Optimizing synchrotron microCT for high-throughput phenotyping of zebrafish

    NASA Astrophysics Data System (ADS)

    La Rivière, Patrick J.; Clark, Darin; Rojek, Alexandra; Vargas, Phillip; Xiao, Xianghui; DeCarlo, Francesco; Kindlmann, Gordon; Cheng, Keith

    2010-09-01

    We are creating a state-of-the-art 2D and 3D imaging atlas of zebrafish development. The atlas employs both 2D histology slides and 3D benchtop and synchrotron micro CT results. Through this atlas, we expect to document normal and abnormal organogenesis, to reveal new levels of structural detail, and to advance image informatics as a form of systems biology. The zebrafish has become a widely used model organism in biological and biomedical research for studies of vertebrate development and gene function. In this work, we will report on efforts to optimize synchrotron microCT imaging parameters for zebrafish at crucial developmental stages. The aim of these studies is to establish protocols for high-throughput phenotyping of normal, mutant and diseased zebrafish. We have developed staining and embedding protocols using different heavy metal stains (osmium tetroxide and uranyl acetate) and different embedding media (Embed 812 and glycol methacrylate). We have explored the use of edge subtraction and multi-energy techniques for contrast enhancement and we have examined the use of different sample-detector distances with unstained samples to explore and optimize phase-contrast enhancement effects. We will report principally on our efforts to optimize energy choice for single- and multi-energy studies as well as our efforts to optimize the degree of phase contrast enhancement.

  5. 3D segmentation of non-isolated pulmonary nodules in high resolution CT images

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangwei; McLennan, Geoffrey; Hoffman, Eric A.; Sonka, Milan

    2005-04-01

    The purpose of this study is to develop a computer-aided diagnosis (CAD) system to segment small size non-isolated pulmonary nodules in high resolution helical CT scans. A new automated method of segmenting juxtapleural nodules was proposed, in which a quadric surface fitting procedure was used to create a boundary between a juxtapleural nodule and its neighboring pleural surface. Experiments on some real CT nodule data showed that this method was able to yield results that reflect the local shape of the pleural surface. Additionally, a scheme based on parametrically deformable geometric model was developed to deal with the problem of segmenting nodules attached to vessels. A vessel segment connected to a nodule was modeled using superquadrics with parametric deformations. The boundary between a vascularized nodule and the attached vessels can be recovered by finding the deformed superquadrics which approximates the vessels. Gradient descent scheme was utilized to optimize the parameters of the superquadrics. Simple experiments on synthetic data showed this scheme is promising.

  6. Computer Aided Evaluation of Ankylosing Spondylitis Using High-Resolution CT

    PubMed Central

    Yao, Jianhua; Ward, Michael M.; Yao, Lawrence; Summers, Ronald M.

    2009-01-01

    Ankylosing Spondylitis is a disease characterized by abnormal bone structures (syndesmophytes) growing at intervertebral disk spaces. Because this growth is so slow as to be undetectable on plain radiographs taken over years, it is desirable to resort to computerized techniques to complement qualitative human judgment with precise quantitative measures. We developed an algorithm with minimal user intervention that provides such measures using high-resolution computed tomography (CT) images. To the best of our knowledge it is the first time that determination of the disease’s status is attempted by direct measurement of the syndesmophytes. The first part of our algorithm segments the whole vertebral body using a 3-D multiscale cascade of successive level sets. The second part extracts the continuous ridgeline of the vertebral body where syndesmophytes are located. For that we designed a novel level set implementation capable of evolving on the isosurface of an object represented by a triangular mesh using curvature features. The third part of the algorithm segments the syndesmophytes from the vertebral body using local cutting planes and quantitates them. We present experimental work done with 10 patients from each of which we processed five vertebrae. The results of our algorithm were validated by comparison with a semi-quantitative evaluation made by a medical expert who visually inspected the CT scans. Correlation between the two evaluations was found to be 0.936 (p < 10−18). PMID:18779065

  7. Nonlinear histogram binning for quantitative analysis of lung tissue fibrosis in high-resolution CT data

    NASA Astrophysics Data System (ADS)

    Zavaletta, Vanessa A.; Bartholmai, Brian J.; Robb, Richard A.

    2007-03-01

    Diffuse lung diseases, such as idiopathic pulmonary fibrosis (IPF), can be characterized and quantified by analysis of volumetric high resolution CT scans of the lungs. These data sets typically have dimensions of 512 x 512 x 400. It is too subjective and labor intensive for a radiologist to analyze each slice and quantify regional abnormalities manually. Thus, computer aided techniques are necessary, particularly texture analysis techniques which classify various lung tissue types. Second and higher order statistics which relate the spatial variation of the intensity values are good discriminatory features for various textures. The intensity values in lung CT scans range between [-1024, 1024]. Calculation of second order statistics on this range is too computationally intensive so the data is typically binned between 16 or 32 gray levels. There are more effective ways of binning the gray level range to improve classification. An optimal and very efficient way to nonlinearly bin the histogram is to use a dynamic programming algorithm. The objective of this paper is to show that nonlinear binning using dynamic programming is computationally efficient and improves the discriminatory power of the second and higher order statistics for more accurate quantification of diffuse lung disease.

  8. High-Resolution CT Imaging of Single Breast Cancer Microcalcifications In Vivo

    PubMed Central

    Inoue, Kazumasa; Liu, Fangbing; Hoppin, Jack; Lunsford, Elaine P.; Lackas, Christian; Hesterman, Jacob; Lenkinski, Robert E.; Fujii, Hirofumi; Frangioni, John V.

    2010-01-01

    Microcalcification is a hallmark of breast cancer and a key diagnostic feature for mammography. We recently described the first robust animal model of breast cancer microcalcification. In this study, we hypothesized that high-resolution computed tomography (CT) could potentially detect the genesis of a single microcalcification in vivo and quantify its growth over time. Using a commercial CT scanner, we systematically optimized acquisition and reconstruction parameters. Two ray-tracing image reconstruction algorithms were tested, a voxel-driven “fast” cone beam algorithm (FCBA) and a detector-driven “exact” cone beam algorithm (ECBA). By optimizing acquisition and reconstruction parameters, we were able to achieve a resolution of 104 µm full-width at half maximum (FWHM). At an optimal detector sampling frequency, ECBA provided a 28 µm (21%) FWHM improvement in resolution over FCBA. In vitro, we were able to image a single 300 µm by 100 µm hydroxyapatite crystal. In a syngeneic rat model of breast cancer, we were able to detect the genesis of a single microcalcification in vivo and follow its growth longitudinally over weeks. Taken together, this study provides an in vivo “gold standard” for the development of calcification-specific contrast agents and a model system for studying the mechanism of breast cancer microcalcification. PMID:21504703

  9. Comparison of the effects of salmon calcitonin (sCT) and calcitonin gene-related peptide (CGRP) in a number of in vivo and in vitro tests

    SciTech Connect

    Welch, S.P.; Brase, D.; Cooper, C.; Dewey, W.L.

    1986-03-05

    sCT and CGRP have been shown previously to have multiple activities in the central nervous system (CNS). Recent work has shown that CGRP (15 ..mu..g) intraventricularly (IVT) produces a naloxone reversible 37% inhibition in the p-phenylquinone test (PPQ) accompanied by severe diarrhea. The ED50 of sCT in the PPQ test is 362 ng and this effect is not reversed totally by naloxone. The onset of CGRP is more rapid than that of sCT. sCT and CGRP (10/sup -6/M) both produce naloxone reversible inhibition of the electrically stimulated guinea pig ileum (GPI) (25% and 50% respectively). Both sCT and CGRP (10/sup -6/ M) produce contracture (15% and 40% respectively) of the non-stimulated GPI that is not blocked by atropine. Both sCT and CGRP block the naloxone-induced contracture of the morphine (MS04) dependent ilea (29% and 68% respectively). Both sCT and CGRP produce biphasic shifts in the MS04 acetylcholine dose-effect curves in the stimulated and nonstimulated GPI, respectively. Neither sCT nor CGRP (10/sup -9/ to 10/sup -4/ M) displaces /sup 3/H-naloxone binding to mouse brain membranes. Both sCT and CGRP may produce their effects by modulation of CA/sup +2/ fluxes in the CNS and GPI.

  10. Deriving effective atomic numbers from DECT based on a parameterization of the ratio of high and low linear attenuation coefficients

    NASA Astrophysics Data System (ADS)

    Landry, Guillaume; Seco, Joao; Gaudreault, Mathieu; Verhaegen, Frank

    2013-10-01

    Dual energy computed tomography (DECT) can provide simultaneous estimation of relative electron density ρe and effective atomic number Zeff. The ability to obtain these quantities (ρe, Zeff) has been shown to benefit selected radiotherapy applications where tissue characterization is required. The conventional analysis method (spectral method) relies on knowledge of the CT scanner photon spectra which may be difficult to obtain accurately. Furthermore an approximate empirical attenuation correction of the photon spectrum through the patient is necessary. We present an alternative approach based on a parameterization of the measured ratio of low and high kVp linear attenuation coefficients for deriving Zeff which does not require the estimation of the CT scanner spectra. In a first approach, the tissue substitute method (TSM), the Rutherford parameterization of the linear attenuation coefficients was employed to derive a relation between Zeff and the ratio of the linear attenuation coefficients measured at the low and high kVp of the CT scanner. A phantom containing 16 tissue mimicking inserts was scanned with a dual source DECT scanner at 80 and 140 kVp. The data from the 16 inserts phantom was used to obtain model parameters for the relation between Zeff and \\mu \\big|_{140kVp}^{80kVp}. The accuracy of the method was evaluated with a second phantom containing 4 tissue mimicking inserts. The TSM was compared to a more complex approach, the reference tissue method (RTM), which requires the derivation of stoichiometric fit parameters. These were derived from the 16 inserts phantom scans and used to calculate CT numbers at 80 and 140 kVp for a set of tabulated reference human tissues. Model parameters for the parameterization of \\mu \\big|_{140\\;kVp}^{80\\;kVp} were estimated for this reference tissue dataset and compared to the results of the TSM. Residuals on Zeff for the reference tissue dataset for both TSM and RTM were compared to those obtained from the

  11. Deriving effective atomic numbers from DECT based on a parameterization of the ratio of high and low linear attenuation coefficients.

    PubMed

    Landry, Guillaume; Seco, Joao; Gaudreault, Mathieu; Verhaegen, Frank

    2013-10-01

    Dual energy computed tomography (DECT) can provide simultaneous estimation of relative electron density ρe and effective atomic number Zeff. The ability to obtain these quantities (ρe, Zeff) has been shown to benefit selected radiotherapy applications where tissue characterization is required. The conventional analysis method (spectral method) relies on knowledge of the CT scanner photon spectra which may be difficult to obtain accurately. Furthermore an approximate empirical attenuation correction of the photon spectrum through the patient is necessary. We present an alternative approach based on a parameterization of the measured ratio of low and high kVp linear attenuation coefficients for deriving Zeff which does not require the estimation of the CT scanner spectra. In a first approach, the tissue substitute method (TSM), the Rutherford parameterization of the linear attenuation coefficients was employed to derive a relation between Zeff and the ratio of the linear attenuation coefficients measured at the low and high kVp of the CT scanner. A phantom containing 16 tissue mimicking inserts was scanned with a dual source DECT scanner at 80 and 140 kVp. The data from the 16 inserts phantom was used to obtain model parameters for the relation between Zeff and [Formula: see text]. The accuracy of the method was evaluated with a second phantom containing 4 tissue mimicking inserts. The TSM was compared to a more complex approach, the reference tissue method (RTM), which requires the derivation of stoichiometric fit parameters. These were derived from the 16 inserts phantom scans and used to calculate CT numbers at 80 and 140 kVp for a set of tabulated reference human tissues. Model parameters for the parameterization of [Formula: see text] were estimated for this reference tissue dataset and compared to the results of the TSM. Residuals on Zeff for the reference tissue dataset for both TSM and RTM were compared to those obtained from the spectral method. The

  12. Flow and Noise Control in High Speed and High Reynolds Number Jets Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Samimy, M.; Kastner, J.; Kim, J.-H.; Utkin, Y.; Adamovich, I.; Brown, C. A.

    2006-01-01

    The idea of manipulating flow to change its characteristics is over a century old. Manipulating instabilities of a jet to increase its mixing and to reduce its radiated noise started in the 1970s. While the effort has been successful in low-speed and low Reynolds number jets, available actuators capabilities in terms of their amplitude, bandwidth, and phasing have fallen short in control of high-speed and high Reynolds number jets of practical interest. Localized arc filament plasma actuators have recently been developed and extensively used at Gas Dynamics and Turbulence Laboratory (GDTL) for control of highspeed and high Reynolds number jets. While the technique has been quite successful and is very promising, all the work up to this point had been carried out using small high subsonic and low supersonic jets from a 2.54 cm diameter nozzle exit with a Reynolds number of about a million. The preliminary work reported in this paper is a first attempt to evaluate the scalability of the technique. The power supply/plasma generator was designed and built in-house at GDTL to operate 8 actuators simultaneously over a large frequency range (0 to 200 kHz) with independent control over phase and duty cycle of each actuator. This allowed forcing the small jet at GDTL with azimuthal modes m = 0, 1, 2, 3, plus or minus 1, plus or minus 2, and plus or minus 4 over a large range of frequencies. This power supply was taken to and used, with minor modifications, at the NASA Nozzle Acoustic Test Rig (NATR). At NATR, 32 actuators were distributed around the 7.5 in. nozzle (a linear increase with nozzle exit diameter would require 60 actuators). With this arrangement only 8 actuators could operate simultaneously, thus limiting the forcing of the jet at NATR to only three azimuthal modes m = plus or minus 1, 4, and 8. Very preliminary results at NATR indicate that the trends observed in the larger NASA facility in terms of the effects of actuation frequency and azimuthal modes are

  13. Normal and pathologic CT anatomy of the mandible

    SciTech Connect

    Osborn, A.G.; Hanafee, W.H.; Mancuso, A.A.

    1982-09-01

    The value of computed tomography (CT) in the diagnosis and management of a wide variety of facial lesions has been amply demonstrated. While a number of studies have focused on CT anatomy of the paranasal sinuses, nose, and nasopharynx, none has concentrated on the mandible. Although the mandible is difficult to image because of its complex, curving surfaces and the presence of artifact-producing amalgam fillings or restorations, CT of the mandible can nevertheless be highly informative in selected cases. This pictorial essay depicts normal gross and CT anatomy of the mandible and presents a series of cases that illustrate the utility of CT in examining mandibular lesions.

  14. The Role of Chest Computed Tomography (CT) as a Surveillance Tool in Children with High-risk Neuroblastoma

    PubMed Central

    Federico, Sara M.; Brady, Samuel L.; Pappo, Alberto; Wu, Jianrong; Mao, Shenghua; McPherson, Valerie J.; Young, Alison; Furman, Wayne L.; Kaufman, Robert; Kaste, Sue

    2015-01-01

    Purpose Standardization of imaging obtained in children with neuroblastoma is not well established. This study examines chest CT in pediatric patients with high-risk neuroblastoma. Methods Medical records and imaging from 88 patients with high-risk neuroblastoma, diagnosed at St. Jude Children's Research Hospital between January, 2002 and December, 2009, were reviewed. Surveillance imaging was conducted through 2013. Ten patients with thoracic disease at diagnosis were excluded. Event free survival (EFS) and overall survival (OS) were estimated. Size specific dose estimates for CT scans of the chest, abdomen, and pelvis were used to estimate absolute organ doses to 23 organs. Organ dosimetry was used to calculate cohort effective dose. Results The 5 year OS and EFS were 51.9%±6.5% and 42.6%±6.5%, respectively. Forty-six (58.9%) patients progressed/recurred and 41 (52.6%) died of disease. Eleven patients (14%) developed thoracic disease progression/recurrence identified by chest CT (1 paraspinal mass, 1 pulmonary nodules, and 9 nodal). MIBG (metaiodobenzylguanidine) scans identified thoracic disease in 6 patients. Five of the 11 had normal chest MIBG scans; 3 were symptomatic and 2 were asymptomatic with normal chest MIBG scans but avid bone disease. The estimated radiation dose savings from surveillance without CT chest imaging was 42%, 34% when accounting for modern CT acquisition (2011-13). Conclusions Neuroblastoma progression/recurrence in the chest is rare and often presents with symptoms or is identified using standard non-CT imaging modalities. For patients with non-thoracic high-risk neuroblastoma at diagnosis, omission of surveillance chest CT imaging can save 35-42% of the radiation burden without compromising disease detection. PMID:25641708

  15. High spatial range velocity measurements in a high Reynolds number turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    de Silva, C. M.; Gnanamanickam, E. P.; Atkinson, C.; Buchmann, N. A.; Hutchins, N.; Soria, J.; Marusic, I.

    2014-02-01

    Here, we detail and analyse a multi-resolution particle image velocity measurement that resolves the wide range of scales prevalent in a zero pressure gradient turbulent boundary layer at high Reynolds numbers (up to Reτ ≈ 20 000). A unique configuration is utilised, where an array of eight high resolution cameras at two magnification levels are used simultaneously to obtain a large field of view, while still resolving the smaller scales prevalent in the flow. Additionally, a highly magnified field of view targeted at the near wall region is employed to capture the viscous sublayer and logarithmic region, with a spatial resolution of a few viscous length scales. Flow statistics from these measurements show good agreement with prior, well resolved hot-wire anemometry measurements. Analysis shows that the instantaneous wall shear stress can be reliably computed, which is historically known to be challenging in boundary layers. A statistical assessment of the wall shear stress shows good agreement with existing correlations, prior experimental and direct numerical simulation data, extending this view to much higher Reynolds numbers. Furthermore, conditional analysis using multiple magnification levels is detailed, to study near-wall events associated with high skin friction fluctuations and their associated overlaying structures in the log region. Results definitively show that the passage of very large-scale positive (or negative) velocity fluctuations are associated with increased (or reduced) small-scale variance in wall shear stress fluctuations.

  16. Detecting metastasis of gastric carcinoma using high-resolution micro-CT system: in vivo small animal study

    NASA Astrophysics Data System (ADS)

    Liu, Junting; Tian, Jie; Liang, Jimin; Li, Xiangsi; Yang, Xiang; Chen, Xiaofeng; Chen, Yi; Zhou, Yuanfang; Wang, Xiaorui

    2011-03-01

    Immunocytochemical and immunofluorescence staining are used for identifying the characteristics of metastasis in traditional ways. Micro-computed tomography (micro-CT) is a useful tool for monitoring and longitudinal imaging of tumor in small animal in vivo. In present study, we evaluated the feasibility of the detection for metastasis of gastric carcinoma by high-resolution micro-CT system with omnipaque accumulative enhancement method in the organs. Firstly, a high-resolution micro-CT ZKKS-MCT-sharp micro-CT was developed by our research group and Guangzhou Zhongke Kaisheng Medical Technology Co., Ltd. Secondly, several gastric carcinoma models were established through inoculating 2x106 BGC-823 gastric carcinoma cells subcutaneously. Thirdly, micro-CT scanning was performed after accumulative enhancement method of intraperitoneal injection of omnipaque contrast agent containing 360 mg iodine with a concentration of 350 mg I/ml. Finally, we obtained high-resolution anatomical information of the metastasis in vivo in a BALB/c NuNu nude mouse, the 3D tumor architecture is revealed in exquisite detail at about 35 μm spatial resolution. In addition, the accurate shape and volume of the micrometastasis as small as 0.78 mm3 can be calculated with our software. Overall, our data suggest that this imaging approach and system could be used to enhance the understanding of tumor proliferation, metastasis and could be the basis for evaluating anti-tumor therapies.

  17. Interaction dynamics of high Reynolds number magnetized plasma flow on the CTIX plasma accelerator

    NASA Astrophysics Data System (ADS)

    Howard, Stephen James

    The Compact Toroid Injection eXperiment, (CTIX), is a coaxial railgun that forms and accelerates magnetized plasma rings called compact toroids (CT's). CTIX consists of a pair of cylindrical coaxial electrodes with the region between them kept at high vacuum (2 m long, 15 cm outer diameter). Hydrogen is typically the dominant constituent of the CT plasma, however helium can also be used. The railgun effect that accelerates the CT can be accounted for by the Lorentz j x B force density created by the power input from a capacitor bank of roughly a Giga-Watt peak. The final velocity of the CT can be as high as 300 km/s, with an acceleration of about 3 billion times Earth's gravity. The compact toroid is able to withstand these forces because of a large internal magnetic field of about 1 Tesla. Understanding the nature of high speed flow of a magnetized plasma has been the primary challenge of this work. In this dissertation we will explore a sequence of fundamental questions regarding the plasma physics of CTIX. First we will go over some new results about the structure and dynamics of the compact toroid's magnetic field, and its electrical resistivity. Then we will present the results from a sequence of key experiments involving reconnection/compression and thermalization of the plasma during interaction of the CT with target magnetic fields of various geometries. Next, we look at the Doppler shift of a spectral line of the He II ion as a measurement of plasma velocity, and to gain insight into the ionization physics of helium in our plasma. These preliminary experiments provide the background for our primary experimental tool for investigating turbulence, a technique called Gas Puff Imaging (GPI) in which a cloud of helium can be used to enhance plasma brightness, allowing plasma density fluctuations to be imaged. We will conclude with an analysis of the images that show coherent density waves, as well as the transition to turbulence during the interaction with a

  18. Extracting material parameters from x-ray attenuation: a CT feasibility study using kilovoltage synchrotron x-rays incident upon low atomic number absorbers.

    PubMed

    Kirby, B J; Davis, J R; Grant, J A; Morgan, M J

    2003-10-21

    The work reported here is a feasibility study of the extraction of material parameters from measurements of the linear x-ray attenuation coefficient of low atomic number absorbers. Computed tomography (CT) scans of small samples containing several liquids and solids were carried out with synchrotron radiation at the Australian National Beamline Facility (BL 20B) in Japan. Average values of the x-ray linear attenuation coefficient were extracted for each material for x-ray energies ranging from 11 keV to 20.5 keV. The electron density was estimated by applying results derived from a parametrization of the x-ray linear attenuation coefficient first developed by Jackson and Hawkes and extended for this work. Average estimates for the electron density of triethanolamine and acetic acid were made to within +5.3% of the actual value. Other materials examined included furfuraldehyde, perspex and teflon, for which average estimates of the electron density were less than 10% in excess of the calculated value. PMID:14620065

  19. Extracting material parameters from x-ray attenuation: a CT feasibility study using kilovoltage synchrotron x-rays incident upon low atomic number absorbers

    NASA Astrophysics Data System (ADS)

    Kirby, B. J.; Davis, J. R.; Grant, J. A.; Morgan, M. J.

    2003-10-01

    The work reported here is a feasibility study of the extraction of material parameters from measurements of the linear x-ray attenuation coefficient of low atomic number absorbers. Computed tomography (CT) scans of small samples containing several liquids and solids were carried out with synchrotron radiation at the Australian National Beamline Facility (BL 20B) in Japan. Average values of the x-ray linear attenuation coefficient were extracted for each material for x-ray energies ranging from 11 keV to 20.5 keV. The electron density was estimated by applying results derived from a parametrization of the x-ray linear attenuation coefficient first developed by Jackson and Hawkes and extended for this work. Average estimates for the electron density of triethanolamine and acetic acid were made to within +5.3% of the actual value. Other materials examined included furfuraldehyde, perspex and teflon, for which average estimates of the electron density were less than 10% in excess of the calculated value.

  20. High-fidelity artifact correction for cone-beam CT imaging of the brain

    NASA Astrophysics Data System (ADS)

    Sisniega, A.; Zbijewski, W.; Xu, J.; Dang, H.; Stayman, J. W.; Yorkston, J.; Aygun, N.; Koliatsos, V.; Siewerdsen, J. H.

    2015-02-01

    CT is the frontline imaging modality for diagnosis of acute traumatic brain injury (TBI), involving the detection of fresh blood in the brain (contrast of 30-50 HU, detail size down to 1 mm) in a non-contrast-enhanced exam. A dedicated point-of-care imaging system based on cone-beam CT (CBCT) could benefit early detection of TBI and improve direction to appropriate therapy. However, flat-panel detector (FPD) CBCT is challenged by artifacts that degrade contrast resolution and limit application in soft-tissue imaging. We present and evaluate a fairly comprehensive framework for artifact correction to enable soft-tissue brain imaging with FPD CBCT. The framework includes a fast Monte Carlo (MC)-based scatter estimation method complemented by corrections for detector lag, veiling glare, and beam hardening. The fast MC scatter estimation combines GPU acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles (sparse MC) augmented by kernel de-noising to yield a runtime of ~4 min per scan. Scatter correction is combined with two-pass beam hardening correction. Detector lag correction is based on temporal deconvolution of the measured lag response function. The effects of detector veiling glare are reduced by deconvolution of the glare response function representing the long range tails of the detector point-spread function. The performance of the correction framework is quantified in experiments using a realistic head phantom on a testbench for FPD CBCT. Uncorrected reconstructions were non-diagnostic for soft-tissue imaging tasks in the brain. After processing with the artifact correction framework, image uniformity was substantially improved, and artifacts were reduced to a level that enabled visualization of ~3 mm simulated bleeds throughout the brain. Non-uniformity (cupping) was reduced by a factor of 5, and contrast of simulated bleeds was improved from ~7 to 49.7 HU, in good agreement

  1. A high-energy-density, high-Mach number single jet experiment

    SciTech Connect

    Hansen, J. F.; Dittrich, T. R.; Elliott, J. B.; Glendinning, S. G.; Cotrell, D. L.

    2011-08-15

    A high-energy-density, x-ray-driven, high-Mach number (M{>=} 17) single jet experiment shows constant propagation speeds of the jet and its bowshock into the late time regime. The jet assumes a characteristic mushroom shape with a stalk and a head. The width of the head and the bowshock also grow linearly in time. The width of the stalk decreases exponentially toward an asymptotic value. In late time images, the stalk kinks and develops a filamentary nature, which is similar to experiments with applied magnetic fields. Numerical simulations match the experiment reasonably well, but ''exterior'' details of the laser target must be included to obtain a match at late times.

  2. Automated Classification of Usual Interstitial Pneumonia using Regional Volumetric Texture Analysis in High-Resolution CT

    PubMed Central

    Depeursinge, Adrien; Chin, Anne S.; Leung, Ann N.; Terrone, Donato; Bristow, Michael; Rosen, Glenn; Rubin, Daniel L.

    2014-01-01

    Objectives We propose a novel computational approach for the automated classification of classic versus atypical usual interstitial pneumonia (UIP). Materials and Methods 33 patients with UIP were enrolled in this study. They were classified as classic versus atypical UIP by a consensus of two thoracic radiologists with more than 15 years of experience using the American Thoracic Society evidence–based guidelines for CT diagnosis of UIP. Two cardiothoracic fellows with one year of subspecialty training provided independent readings. The system is based on regional characterization of the morphological tissue properties of lung using volumetric texture analysis of multiple detector CT images. A simple digital atlas with 36 lung subregions is used to locate texture properties, from which the responses of multi-directional Riesz wavelets are obtained. Machine learning is used to aggregate and to map the regional texture attributes to a simple score that can be used to stratify patients with UIP into classic and atypical subtypes. Results We compared the predictions based on regional volumetric texture analysis with the ground truth established by expert consensus. The area under the receiver operating characteristic curve of the proposed score was estimated to be 0.81 using a leave-one-patient-out cross-validation, with high specificity for classic UIP. The performance of our automated method was found to be similar to that of the two fellows and to the agreement between experienced chest radiologists reported in the literature. However, the errors of our method and the fellows occurred on different cases, which suggests that combining human and computerized evaluations may be synergistic. Conclusions Our results are encouraging and suggest that an automated system may be useful in routine clinical practice as a diagnostic aid for identifying patients with complex lung disease such as classic UIP, obviating the need for invasive surgical lung biopsy and its

  3. Regularization design for high-quality cone-beam CT of intracranial hemorrhage using statistical reconstruction

    NASA Astrophysics Data System (ADS)

    Dang, H.; Stayman, J. W.; Xu, J.; Sisniega, A.; Zbijewski, W.; Wang, X.; Foos, D. H.; Aygun, N.; Koliatsos, V. E.; Siewerdsen, J. H.

    2016-03-01

    Intracranial hemorrhage (ICH) is associated with pathologies such as hemorrhagic stroke and traumatic brain injury. Multi-detector CT is the current front-line imaging modality for detecting ICH (fresh blood contrast 40-80 HU, down to 1 mm). Flat-panel detector (FPD) cone-beam CT (CBCT) offers a potential alternative with a smaller scanner footprint, greater portability, and lower cost potentially well suited to deployment at the point of care outside standard diagnostic radiology and emergency room settings. Previous studies have suggested reliable detection of ICH down to 3 mm in CBCT using high-fidelity artifact correction and penalized weighted least-squared (PWLS) image reconstruction with a post-artifact-correction noise model. However, ICH reconstructed by traditional image regularization exhibits nonuniform spatial resolution and noise due to interaction between the statistical weights and regularization, which potentially degrades the detectability of ICH. In this work, we propose three regularization methods designed to overcome these challenges. The first two compute spatially varying certainty for uniform spatial resolution and noise, respectively. The third computes spatially varying regularization strength to achieve uniform "detectability," combining both spatial resolution and noise in a manner analogous to a delta-function detection task. Experiments were conducted on a CBCT test-bench, and image quality was evaluated for simulated ICH in different regions of an anthropomorphic head. The first two methods improved the uniformity in spatial resolution and noise compared to traditional regularization. The third exhibited the highest uniformity in detectability among all methods and best overall image quality. The proposed regularization provides a valuable means to achieve uniform image quality in CBCT of ICH and is being incorporated in a CBCT prototype for ICH imaging.

  4. A complete CAD system for pulmonary nodule detection in high resolution CT images

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangwei; McLennan, Geoffrey; Hoffman, Eric A.; Sonka, Milan

    2005-04-01

    The purpose of this study is to develop a computer-aided diagnosis (CAD) system to detect small-sized (from 2mm to 10mm) pulmonary nodules in high resolution helical CT scans. A new CAD system is proposed to locate both juxtapleural nodules and non-pleural nodules. Isotropic resampling and lung segmentation are performed as preprocessing steps. Morphological closing was utilized to smooth the lung contours to include the indented possible juxtapleural locations, thresholding and 3D component analysis were used to obtain 3D volumetric nodule candidates; furthermore, gray level and geometric features were extracted, and analyzed using linear discriminant analysis (LDA) classifier. Leave one case out method was used to evaluate the LDA. To deal with non-pleural nodules, a discrete-time cellular neural network (DTCNN) based on local shape features was developed. This scheme employed the local shape property to perform voxel classification. The shape index feature successfully captured the local shape difference between nodules and non-nodules, especially vessels. To tailor it for lung nodule detection, this DTCNN was trained using genetic algorithms (GAs) to derive the shape index variation pattern of nodules. Nonoverlapping training and testing sets were utilized in the non-pleural nodule detection. 19 clinical thoracic CT cases involving a total of 4838 sectional images were used in this work. The juxtapleural nodule detection method was able to obtain sensitivity 81.25% with an average of 8.29 FPs per case. The non-pleural nodule finding scheme attained sensitivity of 83.9% with an average 3.47 FPs/case. Combining the two subsystems together, an overall performance of 82.98% sensitivity with 11.76 FPs/case can be obtained.

  5. Optimization of a retrospective technique for respiratory-gated high speed micro-CT of free-breathing rodents

    NASA Astrophysics Data System (ADS)

    Ford, Nancy L.; Wheatley, Andrew R.; Holdsworth, David W.; Drangova, Maria

    2007-09-01

    The objective of this study was to develop a technique for dynamic respiratory imaging using retrospectively gated high-speed micro-CT imaging of free-breathing mice. Free-breathing C57Bl6 mice were scanned using a dynamic micro-CT scanner, comprising a flat-panel detector mounted on a slip-ring gantry. Projection images were acquired over ten complete gantry rotations in 50 s, while monitoring the respiratory motion in synchrony with projection-image acquisition. Projection images belonging to a selected respiratory phase were retrospectively identified and used for 3D reconstruction. The effect of using fewer gantry rotations—which influences both image quality and the ability to quantify respiratory function—was evaluated. Images reconstructed using unique projections from six or more gantry rotations produced acceptable images for quantitative analysis of lung volume, CT density, functional residual capacity and tidal volume. The functional residual capacity (0.15 ± 0.03 mL) and tidal volumes (0.08 ± 0.03 mL) measured in this study agree with previously reported measurements made using prospectively gated micro-CT and at higher resolution (150 µm versus 90 µm voxel spacing). Retrospectively gated micro-CT imaging of free-breathing mice enables quantitative dynamic measurement of morphological and functional parameters in the mouse models of respiratory disease, with scan times as short as 30 s, based on the acquisition of projection images over six gantry rotations.

  6. High-Performance Soft-Tissue Imaging in Extremity Cone-Beam CT

    PubMed Central

    Zbijewski, W.; Sisniega, A.; Stayman, J. W.; Muhit, A.; Thawait, G.; Packard, N.; Senn, R.; Yang, D.; Yorkston, J.; Carrino, J. A.; Siewerdsen, J. H.

    2014-01-01

    Purpose Clinical performance studies of an extremity cone-beam CT (CBCT) system indicate excellent bone visualization, but point to the need for improvement of soft-tissue image quality. To this end, a rapid Monte Carlo (MC) scatter correction is proposed, and Penalized Likelihood (PL) reconstruction is evaluated for noise management. Methods The accelerated MC scatter correction involved fast MC simulation with low number of photons implemented on a GPU (107 photons/sec), followed by Gaussian kernel smoothing in the detector plane and across projection angles. PL reconstructions were investigated for reduction of imaging dose for projections acquired at ~2 mGy. Results The rapid scatter estimation yielded root-mean-squared-errors of scatter projections of ~15% of peak scatter intensity for 5·106 photons/projection (runtime ~0.5 sec/projection) and 25% improvement in fat-muscle contrast in reconstructions of a cadaveric knee. PL reconstruction largely restored soft-tissue visualization at 2 mGy dose to that of 10 mGy FBP image. Conclusion The combination of rapid (5–10 minutes/scan) MC-based, patient-specific scatter correction and PL reconstruction offers an important means to overcome the current limitations of extremity CBCT in soft-tissue imaging. PMID:25076825

  7. High-performance soft-tissue imaging in extremity cone-beam CT

    NASA Astrophysics Data System (ADS)

    Zbijewski, W.; Sisniega, A.; Stayman, J. W.; Muhit, A.; Thawait, G.; Packard, N.; Senn, R.; Yang, D.; Yorkston, J.; Carrino, J. A.; Siewerdsen, J. H.

    2014-03-01

    Purpose: Clinical performance studies of an extremity cone-beam CT (CBCT) system indicate excellent bone visualization, but point to the need for improvement of soft-tissue image quality. To this end, a rapid Monte Carlo (MC) scatter correction is proposed, and Penalized Likelihood (PL) reconstruction is evaluated for noise management. Methods: The accelerated MC scatter correction involved fast MC simulation with low number of photons implemented on a GPU (107 photons/sec), followed by Gaussian kernel smoothing in the detector plane and across projection angles. PL reconstructions were investigated for reduction of imaging dose for projections acquired at ~2 mGy. Results: The rapid scatter estimation yielded root-mean-squared-errors of scatter projections of ~15% of peak scatter intensity for 5ṡ106 photons/projection (runtime ~0.5 sec/projection) and 25% improvement in fat-muscle contrast in reconstructions of a cadaveric knee. PL reconstruction largely restored soft-tissue visualization at 2 mGy dose to that of 10 mGy FBP image. Conclusion: The combination of rapid (5-10 minutes/scan) MC-based, patient-specific scatter correction and PL reconstruction offers an important means to overcome the current limitations of extremity CBCT in soft-tissue imaging.

  8. HIGH-z QUASARS IN THE R {sub h} = ct UNIVERSE

    SciTech Connect

    Melia, Fulvio

    2013-02-10

    One cannot understand the early appearance of 10{sup 9} M {sub Sun} supermassive black holes without invoking anomalously high accretion rates or the creation of exotically massive seeds, neither of which is seen in the local universe. Recent observations have compounded this problem by demonstrating that most, if not all, of the high-z quasars appear to be accreting at the Eddington limit. In the context of {Lambda}CDM, the only viable alternative now appears to be the assemblage of supermassive black holes via mergers, as long as the seeds started forming at redshifts >40, but ceased being created by z {approx} 20-30. In this paper, we show that, whereas the high-z quasars may be difficult to explain within the framework of the standard model, they can instead be interpreted much more sensibly in the context of the R {sub h} = ct universe. In this cosmology, 5-20 M {sub Sun} seeds produced after the onset of re-ionization (at z {approx}< 15) could have easily grown to M {approx}> 10{sup 9} M {sub Sun} by z {approx}> 6, merely by accreting at the standard Eddington rate.

  9. High level cross of the esophagus with the descending aorta in scoliosis: CT study

    SciTech Connect

    Takahashi, Koji; Kikuno, Motoyuki; Hyodoh, Hideki

    1996-05-01

    The esophagus occasionally crosses the descending aorta at an unusually high level (3-5 cm inferior to the carina) in right-sided scoliosis. The purpose of this study was to analyze the mechanism of this finding. We prospectively evaluated thoracic CT scans in 30 patients with right-sided scoliosis. We assessed the alterations in the positions of the esophagus and the descending aorta by the thoracic deformity. The descending aorta followed the scoliotic curve of the spine in 26 (87%) patients. The esophagus followed the scoliotic curve of the spine in 14 (47%) patients and did not in 16 (53%). The anteroposterior diameter of the thorax in the former group was significantly smaller than that in the latter (p < 0.01). High level cross of both structures was identified in 14 (47%) patients, and all of them belonged to the group in which the esophagus did not follow the scoliotic curve of the spine. The unusual high level cross of the esophagus with the descending aorta occasionally seen in scoliosis is due to a difference in the positional alterations of the two structures resulting from the scoliosis. 6 refs., 3 figs.

  10. A computer simulation method for low-dose CT images by use of real high-dose images: a phantom study.

    PubMed

    Takenaga, Tomomi; Katsuragawa, Shigehiko; Goto, Makoto; Hatemura, Masahiro; Uchiyama, Yoshikazu; Shiraishi, Junji

    2016-01-01

    Practical simulations of low-dose CT images have a possibility of being helpful means for optimization of the CT exposure dose. Because current methods reported by several researchers are limited to specific vendor platforms and generally rely on raw sinogram data that are difficult to access, we have developed a new computerized scheme for producing simulated low-dose CT images from real high-dose images without use of raw sinogram data or of a particular phantom. Our computerized scheme for low-dose CT simulation was based on the addition of a simulated noise image to a real high-dose CT image reconstructed by the filtered back-projection algorithm. First, a sinogram was generated from the forward projection of a high-dose CT image. Then, an additional noise sinogram resulting from use of a reduced exposure dose was estimated from a predetermined noise model. Finally, a noise CT image was reconstructed with a predetermined filter and was added to the real high-dose CT image to create a simulated low-dose CT image. The noise power spectrum and modulation transfer function of the simulated low-dose images were very close to those of the real low-dose images. In order to confirm the feasibility of our method, we applied this method to clinical cases which were examined with the high dose initially and then followed with a low-dose CT. In conclusion, our proposed method could simulate the low-dose CT images from their real high-dose images with sufficient accuracy and could be used for determining the optimal dose setting for various clinical CT examinations. PMID:26290269

  11. Value of Combined PET/CT for Radiation Planning in CT-Guided Percutaneous Interstitial High-Dose-Rate Single-Fraction Brachytherapy for Colorectal Liver Metastases

    SciTech Connect

    Steffen, Ingo G.; Wust, Peter; Ruehl, Ricarda

    2010-07-15

    Purpose: To determine the additional value of fluorodeoxyglucose-positron emission tomography (PET) for clinical target volume definition in the planning of computed tomography (CT)-guided interstitial brachytherapy for liver metastases. Patients and Methods: A total of 19 patients with liver metastases from colorectal cancer treated in 25 sessions were included in the present study. All patients had undergone fluorodeoxyglucose-PET for patient evaluation before interstitial CT-guided brachytherapy. A contrast-enhanced CT scan of the upper abdomen was obtained for radiation planning. The clinical target volume (CTV) was defined by a radiation oncologist and radiologist. After registration of the CT scan with the PET data set, the target volume was defined again using the fusion images. Results: PET revealed one additional liver lesion that was not visible on CT. The median CT-CTV (defined using CT and magnetic resonance imaging) was 68 cm{sup 3} (range 4-260). The PET/CT-CTV (median, 78 cm{sup 3}; range, 4-273) was significantly larger, with a median gain of 24.5% (interquartile range, 2.1-71.5%; p = .022). An increased CTV was observed in 15 cases and a decrease in 6; in 4 cases, the CT-CTV and PET/CT-CTV were equal. Incomplete dose coverage of PET/CT-CTVs was indicative of early local progression (p = .004); however, CT-based radiation plans did not show significant differences in the local control rates when stratified by dose coverage. Conclusion: Retrospective implementation of fluorodeoxyglucose-PET for CTV specification for CT-guided brachytherapy for colorectal liver metastases revealed a significant change in the CTVs. Additional PET-positive tumor regions with incomplete dose coverage could explain unexpected early local progression.

  12. An approach to segment lung pleura from CT data with high precision

    NASA Astrophysics Data System (ADS)

    Angelats, E.; Chaisaowong, K.; Knepper, A.; Kraus, T.; Aach, T.

    2008-03-01

    A new approach to segment pleurae from CT data with high precision is introduced. This approach is developed in the segmentation's framework of an image analysis system to automatically detect pleural thickenings. The new technique to carry out the 3D segmentation of lung pleura is based on supervised range-constrained thresholding and a Gibbs-Markov random field model. An initial segmentation is done using the 3D histogram by supervised range-constrained thresholding. 3D connected component labelling is then applied to find the thorax. In order to detect and remove trachea and bronchi therein, the 3D histogram of connected pulmonary organs is modelled as a finite mixture of Gaussian distributions. Parameters are estimated using the Expectation-Maximization algorithm, which leads to the classification of that pulmonary region. As consequence left and right lungs are separated. Finally we apply a Gibbs-Markov random field model to our initial segmentation in order to achieve a high accuracy segmentation of lung pleura. The Gibbs- Markov random field is combined with maximum a posteriori estimation to estimate optimal pleural contours. With these procedures, a new segmentation strategy is developed in order to improve the reliability and accuracy of the detection of pleural contours and to achieve a better assessment performance of pleural thickenings.

  13. High-Pitch Coronary CT Angiography at 70 kVp With Low Contrast Medium Volume

    PubMed Central

    Zhang, Long Jiang; Qi, Li; De Cecco, Carlo N.; Zhou, Chang Sheng; Spearman, James V.; Schoepf, U. Joseph; Lu, Guang Ming

    2014-01-01

    Abstract The purpose of this article is to evaluate image quality and radiation dose of prospectively electrocardiogram (ECG)-triggered high-pitch coronary computed tomography angiography (CCTA) at 70 kVp and 30 mL contrast medium. One hundred fifty patients with a heart rate ≤70 beats per minute (bpm) underwent CCTA using a second-generation dual-source computed tomography (CT) scanner and were randomized into 3 groups according to tube voltage and contrast medium volume (370 mg/mL iodine concentration) (100 kVp group, 100 kVp/60 mL, n = 55; 80 kVp group, 80 kVp/60 mL, n = 44; 70 kVp group, 70 kVp/30 mL, n = 51). Objective and subjective image quality along with the effect of heart rate (HR) and body mass index (BMI) was evaluated and compared between the groups. Radiation dose was estimated for each patient. CT attenuation and image noise were higher in the 80 and 70 kVp groups than in the 100 kVp group (all P < 0.001). Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were lower in the 70 kVp group than in the 80 and 100 kVp groups (all P < 0.05). There was no difference for subjective image quality between the groups (P > 0.05). HR did not affect subjective image quality (all P > 0.05), while patients with BMI <23 kg/m2 had higher image quality than patients with BMI ≥23 kg/m2 (P < 0.05). Compared with the 100 kVp group, the radiation dose of the 70 kVp group was reduced by 75%. In conclusion, prospectively ECG-triggered high-pitch 70 kVp/30 mL CCTA can obtain diagnostic image quality with lower radiation dose in selected patients with BMI <23 kg/m2 compared with 80/100 kVp/60 mL CCTA. PMID:25396334

  14. ESTIMATION OF GIARDIA CT VALUES AT HIGH PH FOR THE SURFACE WATER TREATMENT RULE

    EPA Science Inventory

    The U.S. Environmental Protection Agency currently recommends Ct (disinfectant concentration multiplied by the exposure time) values to achieve required levels of inactivation of Giardia lamblia cysts by different disinfectants including free chlorine. Current guidance covers ina...

  15. N-231 High Reynolds Number Channel I is a blowdown Facility that utilizes interchangeable test

    NASA Technical Reports Server (NTRS)

    1980-01-01

    N-231 High Reynolds Number Channel I is a blowdown Facility that utilizes interchangeable test sections and nozzles. The facility provides experimental support for the fluid mechanics research, including experimental verification of aerodynamic computer codes and boundary-layer and airfoil studies that require high Reynolds number simulation. (Tunnel 1)

  16. Comparison of quantitative myocardial perfusion imaging CT to fluorescent microsphere-based flow from high-resolution cryo-images

    NASA Astrophysics Data System (ADS)

    Eck, Brendan L.; Fahmi, Rachid; Levi, Jacob; Fares, Anas; Wu, Hao; Li, Yuemeng; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

    2016-03-01

    Myocardial perfusion imaging using CT (MPI-CT) has the potential to provide quantitative measures of myocardial blood flow (MBF) which can aid the diagnosis of coronary artery disease. We evaluated the quantitative accuracy of MPI-CT in a porcine model of balloon-induced LAD coronary artery ischemia guided by fractional flow reserve (FFR). We quantified MBF at baseline (FFR=1.0) and under moderate ischemia (FFR=0.7) using MPI-CT and compared to fluorescent microsphere-based MBF from high-resolution cryo-images. Dynamic, contrast-enhanced CT images were obtained using a spectral detector CT (Philips Healthcare). Projection-based mono-energetic images were reconstructed and processed to obtain MBF. Three MBF quantification approaches were evaluated: singular value decomposition (SVD) with fixed Tikhonov regularization (ThSVD), SVD with regularization determined by the L-Curve criterion (LSVD), and Johnson-Wilson parameter estimation (JW). The three approaches over-estimated MBF compared to cryo-images. JW produced the most accurate MBF, with average error 33.3+/-19.2mL/min/100g, whereas LSVD and ThSVD had greater over-estimation, 59.5+/-28.3mL/min/100g and 78.3+/-25.6 mL/min/100g, respectively. Relative blood flow as assessed by a flow ratio of LAD-to-remote myocardium was strongly correlated between JW and cryo-imaging, with R2=0.97, compared to R2=0.88 and 0.78 for LSVD and ThSVD, respectively. We assessed tissue impulse response functions (IRFs) from each approach for sources of error. While JW was constrained to physiologic solutions, both LSVD and ThSVD produced IRFs with non-physiologic properties due to noise. The L-curve provided noise-adaptive regularization but did not eliminate non-physiologic IRF properties or optimize for MBF accuracy. These findings suggest that model-based MPI-CT approaches may be more appropriate for quantitative MBF estimation and that cryo-imaging can support the development of MPI-CT by providing spatial distributions of MBF.

  17. Image-Based Motion Compensation for High-Resolution Extremities Cone-Beam CT

    PubMed Central

    Sisniega, A.; Stayman, J. W.; Cao, Q.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.

    2016-01-01

    Purpose Cone-beam CT (CBCT) of the extremities provides high spatial resolution, but its quantitative accuracy may be challenged by involuntary sub-mm patient motion that cannot be eliminated with simple means of external immobilization. We investigate a two-step iterative motion compensation based on a multi-component metric of image sharpness. Methods Motion is considered with respect to locally rigid motion within a particular region of interest, and the method supports application to multiple locally rigid regions. Motion is estimated by maximizing a cost function with three components: a gradient metric encouraging image sharpness, an entropy term that favors high contrast and penalizes streaks, and a penalty term encouraging smooth motion. Motion compensation involved initial coarse estimation of gross motion followed by estimation of fine-scale displacements using high resolution reconstructions. The method was evaluated in simulations with synthetic motion (1–4 mm) applied to a wrist volume obtained on a CMOS-based CBCT testbench. Structural similarity index (SSIM) quantified the agreement between motion-compensated and static data. The algorithm was also tested on a motion contaminated patient scan from dedicated extremities CBCT. Results Excellent correction was achieved for the investigated range of displacements, indicated by good visual agreement with the static data. 10–15% improvement in SSIM was attained for 2–4 mm motions. The compensation was robust against increasing motion (4% decrease in SSIM across the investigated range, compared to 14% with no compensation). Consistent performance was achieved across a range of noise levels. Significant mitigation of artifacts was shown in patient data. Conclusion The results indicate feasibility of image-based motion correction in extremities CBCT without the need for a priori motion models, external trackers, or fiducials. PMID:27346909

  18. Image-based motion compensation for high-resolution extremities cone-beam CT

    NASA Astrophysics Data System (ADS)

    Sisniega, A.; Stayman, J. W.; Cao, Q.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.

    2016-03-01

    Purpose: Cone-beam CT (CBCT) of the extremities provides high spatial resolution, but its quantitative accuracy may be challenged by involuntary sub-mm patient motion that cannot be eliminated with simple means of external immobilization. We investigate a two-step iterative motion compensation based on a multi-component metric of image sharpness. Methods: Motion is considered with respect to locally rigid motion within a particular region of interest, and the method supports application to multiple locally rigid regions. Motion is estimated by maximizing a cost function with three components: a gradient metric encouraging image sharpness, an entropy term that favors high contrast and penalizes streaks, and a penalty term encouraging smooth motion. Motion compensation involved initial coarse estimation of gross motion followed by estimation of fine-scale displacements using high resolution reconstructions. The method was evaluated in simulations with synthetic motion (1-4 mm) applied to a wrist volume obtained on a CMOS-based CBCT testbench. Structural similarity index (SSIM) quantified the agreement between motion-compensated and static data. The algorithm was also tested on a motion contaminated patient scan from dedicated extremities CBCT. Results: Excellent correction was achieved for the investigated range of displacements, indicated by good visual agreement with the static data. 10-15% improvement in SSIM was attained for 2-4 mm motions. The compensation was robust against increasing motion (4% decrease in SSIM across the investigated range, compared to 14% with no compensation). Consistent performance was achieved across a range of noise levels. Significant mitigation of artifacts was shown in patient data. Conclusion: The results indicate feasibility of image-based motion correction in extremities CBCT without the need for a priori motion models, external trackers, or fiducials.

  19. Seventh-generation CT

    NASA Astrophysics Data System (ADS)

    Besson, G. M.

    2016-03-01

    A new dual-drum CT system architecture has been recently introduced with the potential to achieve significantly higher temporal resolution than is currently possible in medical imaging CT. The concept relies only on known technologies; in particular rotation speeds several times higher than what is possible today could be achieved leveraging typical x-ray tube designs and capabilities. However, the architecture lends itself to the development of a new arrangement of x-ray sources in a toroidal vacuum envelope containing a rotating cathode ring and a (optionally rotating) shared anode ring to potentially obtain increased individual beam power as well as increase total exposure per rotation. The new x-ray source sub-system design builds on previously described concepts and could make the provision of multiple conventional high-power cathodes in a CT system practical by distributing the anode target between the cathodes. In particular, relying on known magnetic-levitation technologies, it is in principle possible to more than double the relative speed of the electron-beam with respect to the target, thus potentially leading to significant individual beam power increases as compared to today's state-of-the-art. In one embodiment, the proposed design can be naturally leveraged by the dual-drum CT concept previously described to alleviate the problem of arranging a number of conventional rotating anode-stem x-ray tubes and power conditioners on the limited space of a CT gantry. In another embodiment, a system with three cathodes is suggested leveraging the architecture previously proposed by Franke.

  20. Irrecoverable pressure loss coefficients for two out-of-plane piping elbows at high Reynolds number

    SciTech Connect

    Coffield, R.D.; Hammond, R.B.; McKeown, P.T.

    1999-02-08

    Pressure drops of multiple piping elbows were experimentally determined for high Reynolds number flows. The testing described has been performed in order to reduce uncertainties in the currently used methods for predicting irrecoverable pressure losses and also to provide a qualification database for computational fluid dynamics (CFD) computer codes. The earlier high Reynolds number correlations had been based on extrapolations over several orders of magnitude in Reynolds number from where the original database existed. Recent single elbow test data shows about a factor of two lower elbow pressure loss coefficient (at 40x 106 Reynolds number) than those from current correlations. This single piping elbow data has been extended in this study to a multiple elbow configuration of two elbows that are 90o out-of-plane relative to each other. The effects of separation distance and Reynolds number have been correlated and presented in a form that can be used for design application. Contrary to earlier extrapolations from low Reynolds numbers (Re c 1.0x 106), a strong Reynolds number dependence was found to exist. The combination of the high Reynolds number single elbow data with the multiple elbow interaction effects measured in this study shows that earlier design correlations are conservative by significant margins at high Reynolds numbers. Qualification of CFD predictions with this new high Reynolds number database will help guide the need for additional high Reynolds number testing of other piping configurations. The study also included velocity measurements at several positions downstream of the first and second test elbows using an ultrasonic flowmeter. Reasonable agreement after the first test elbow was found relative to flow fields that are known to exist from low Reynolds number visual tests and also from CFD predictions. This data should help to qualify CFD predictions of the three-dimensional flow stream downstream of the second test elbow.

  1. Irrecoverable pressure loss coefficients for a short radius of curvature piping elbow at high Reynolds numbers

    SciTech Connect

    Coffield, R.D.; Hammond, R.B.; Koczko, J.P.; McKeown, P.T.; Zirpoli, P.J.

    1998-06-01

    Pressure drops in a piping elbow are experimentally determined for high Reynolds number flows. The testing described has been performed in order to reduce uncertainties in the currently used design values for predicting irrecoverable pressure losses. The earlier high Reynolds number correlations had been based on extrapolations over several orders of magnitude in Reynolds number from where the original database existed. The test data shows about a factor of two lower elbow pressure loss coefficient (at 40 {times} 10{sup 6} Reynolds number) than those current correlations.

  2. Large Eddy Simulations of Kelvin Helmholtz instabilities at high Reynolds number stratified flows

    NASA Astrophysics Data System (ADS)

    Brown, Dana; Goodman, Lou; Raessi, Mehdi

    2015-11-01

    Simulations of Kelvin Helmholtz Instabilities (KHI) at high Reynolds numbers are performed using the Large Eddy Simulation technique. Reynolds numbers up to 100,000 are achieved using our model. The resulting data set is used to examine the effect of Reynolds number on various statistics, including dissipation flux coefficient, turbulent kinetic energy budget, and Thorpe length scale. It is shown that KHI are qualitatively different at high Re, up to and including the onset of vortex pairing and billow collapse and quantitatively different afterward. The effect of Richardson number is also examined. The results are discussed as they apply to ocean experiments.

  3. Aerodynamics and heat transfer investigations on a high Reynolds number turbine cascade

    NASA Technical Reports Server (NTRS)

    Schobeiri, Taher; Mcfarland, Eric; Yeh, Frederick

    1991-01-01

    The results of aerodynamic and heat transfer experimental investigations performed in a high Reynolds number turbine cascade test facility are analyzed. The experimental facility simulates the high Reynolds number flow conditions similar to those encountered in the Space Shuttle Main Engine. In order to determine the influence of Reynolds number on aerodynamic and thermal behavior of the blades, heat transfer coefficients were measured at various Reynolds numbers using liquid crystal temperature measurement technique. Potential flow calculation methods were used to predict the cascade pressure distributions. Boundary layer and heat transfer calculation methods were used with these pressure distributions to verify the experimental results.

  4. High Fidelity System Modeling for High Quality Image Reconstruction in Clinical CT

    PubMed Central

    Do, Synho; Karl, William Clem; Singh, Sarabjeet; Kalra, Mannudeep; Brady, Tom; Shin, Ellie; Pien, Homer

    2014-01-01

    Today, while many researchers focus on the improvement of the regularization term in IR algorithms, they pay less concern to the improvement of the fidelity term. In this paper, we hypothesize that improving the fidelity term will further improve IR image quality in low-dose scanning, which typically causes more noise. The purpose of this paper is to systematically test and examine the role of high-fidelity system models using raw data in the performance of iterative image reconstruction approach minimizing energy functional. We first isolated the fidelity term and analyzed the importance of using focal spot area modeling, flying focal spot location modeling, and active detector area modeling as opposed to just flying focal spot motion. We then compared images using different permutations of all three factors. Next, we tested the ability of the fidelity terms to retain signals upon application of the regularization term with all three factors. We then compared the differences between images generated by the proposed method and Filtered-Back-Projection. Lastly, we compared images of low-dose in vivo data using Filtered-Back-Projection, Iterative Reconstruction in Image Space, and the proposed method using raw data. The initial comparison of difference maps of images constructed showed that the focal spot area model and the active detector area model also have significant impacts on the quality of images produced. Upon application of the regularization term, images generated using all three factors were able to substantially decrease model mismatch error, artifacts, and noise. When the images generated by the proposed method were tested, conspicuity greatly increased, noise standard deviation decreased by 90% in homogeneous regions, and resolution also greatly improved. In conclusion, the improvement of the fidelity term to model clinical scanners is essential to generating higher quality images in low-dose imaging. PMID:25390888

  5. Calculation of the vacuum Green's function valid for high toroidal mode number in tokamaks.

    NASA Astrophysics Data System (ADS)

    Chance, Morrell; Turnbull, Alan

    2005-10-01

    The present evaluation of the Green's function used for the magmetic scalar potential in vacuum calculations for axisymmetric geometry in the vacuum segments of gato, pest and other mhd stability codes has been found to be deficient for moderately high toroidal mode numbers. This was due to the loss of numerical precision arising from the upward recursion relation used for generating the functions to high mode numbers. The recursion is initiated from the complete elliptic integrals of the first and second kinds. To ameliorate this, a direct integration of the integral representation of the function was crafted to achieve the necessary high accuracy for moderately high mode numbers. At very high mode numbers the loss of numerical precision due to the oscillatory behavior of the integrand is further avoided by judiciously deforming the integration contour in the complex plane. Machine precision, roughly 14 -- 16 digits, accuracy can be achieved by using a combination of both these techniques.

  6. High Reynolds number analysis of an axisymmetric afterbody with flow separation

    NASA Technical Reports Server (NTRS)

    Carlson, John R.; Reubush, David E.

    1996-01-01

    The ability of a three-dimensional Navier-Stokes method, PAB3D, to predict nozzle afterbody flow at high Reynolds number was assessed. Predicted surface pressure coefficient distributions and integrated afterbody drag are compared with experimental data obtained from the NASA-Langley 0.3 m Transonic Cryogenic Tunnel. Predicted afterbody surface pressures matched experimental data fairly closely. The change in the pressure coefficient distribution with Reynolds number was slightly over-predicted. Integrated afterbody drag was typically high compared to the experimental data. The change in afterbody pressure drag with Reynolds number was fairly small. The predicted point of flow separation on the nozzle was slightly downstream of that observed from oilflow data at low Reynolds numbers and had a very slight Reynolds number dependence, moving slightly further downstream as Reynolds number increased.

  7. Simulations of high-Mach-number collisionless perpendicular shocks in astrophysical plasmas

    NASA Technical Reports Server (NTRS)

    Quest, K. B.

    1985-01-01

    A problem of critical importance to space physics and astrophysics is the existence and properties of high-Mach-number shocks. Preliminary results of a simulation of a perpendicular shock with Alfven Mach number 22 are reported. It is shown that for sufficiently small electron resistivity the dissipation for this shock is provided by a periodic rather than time-stationary reflection of ions. The problem of electron heating and the extension to higher Mach numbers are discussed.

  8. High prevalence of brain pathology in violent prisoners: a qualitative CT and MRI scan study.

    PubMed

    Schiltz, Kolja; Witzel, Joachim G; Bausch-Hölterhoff, Josef; Bogerts, Bernhard

    2013-10-01

    The aim of this study was to determine the frequency and extent of brain anomalies in a large sample of incarcerated violent offenders not previously considered neuropsychiatrically ill, in comparison with non-violent offenders and non-offending controls. MRI and CT brain scans from 287 male prison inmates (162 violent and 125 non-violent) not diagnosed as mentally ill before that were obtained due to headache, vertigo or psychological complaints during imprisonment were assessed and compared to 52 non-criminal controls. Brain scans were rated qualitatively with respect to evidence of structural brain damage. Each case received a semiquantitative rating of "normal" (=0), "questionably abnormal" (=1) or "definitely abnormal" (=2) for the lateral ventricles, frontal/parietal cortex and medial temporal structures bilaterally as well as third ventricle. Overall, offenders displayed a significantly higher rate of morphological abnormality, with the violent offenders scoring significantly higher than non-violent offenders and controls. This difference was statistically detectable for frontal/parietal cortex, medial temporal structures, third ventricle and the left but not the right lateral ventricle. The remarkable prevalence of brain pathology in convicted violent prisoners detectable by neuroradiological routine assessment not only highlights the importance of frontal and temporal structures in the control of social, and specifically of violent behaviour, but also raises questions on the legal culpability of violent offenders with brain abnormalities. The high proportion of undetected presence of structural brain damage emphasizes the need that in violent criminals, the comprehensive routine neuropsychiatric assessment usually performed in routine forensic psychiatric expertises should be complemented with brain imaging. PMID:23568089

  9. Preliminary Application of High-Definition CT Gemstone Spectral Imaging in Hand and Foot Tendons

    PubMed Central

    Deng, Kai; Li, Wei; Wang, Jun-Jun; Wang, Xin-Yi; Pang, Tao; Wang, Guang-Li; Liu, Cheng

    2012-01-01

    Objective To assess the feasibility of visualizing hand and foot tendon anatomy and disorders by Gemstone Spectral Imaging (GSI) high-definition CT (HDCT). Materials and Methods Thirty-five patients who suffered from hand or foot pain were scanned with GSI mode HDCT and MRI. Spectrum analysis was used to select the monochromatic images that provide the optimal contrast-to-noise ratio (CNR) for tendons. The image quality at the best selected monochromatic level and the conventional polychromatic images were compared. Tendon anatomy and disease were also analyzed at GSI and MRI. Results The monochromatic images at about 65 keV (mean 65.09 ± 2.98) provided the optimal CNR for hand and foot tendons. The image quality at the optimal selected monochromatic level was superior to conventional polychromatic images (p = 0.005, p < 0.05). GSI was useful in visualizing hand and foot tendon anatomy and disorders. There were no statistical differences between GSI and MRI with regard to tendon thickening (χ2 = 0, p > 0.05), compression (χ2 = 0.5, p > 0.05), absence (χ2 = 0, p > 0.05) and rupture (χ2 = 0, p > 0.05). GSI was significantly less sensitive than MRI in displaying tendon adhesion (χ2 = 4.17, p < 0.05), degeneration (χ2 = 4.17, p < 0.05), and tendinous sheath disease (χ2 = 10.08, p < 0.05). Conclusion GSI with monochromatic images at 65 keV displays clearly the most hand and foot tendon anatomy and disorders with image quality improved, as compared with conventional polychromatic images. It may be used solely or combined with MRI in clinical work, depending on individual patient disease condition. PMID:23118573

  10. Reynolds Number Effects on a Supersonic Transport at Subsonic High-Lift Conditions (Invited)

    NASA Technical Reports Server (NTRS)

    Owens, L.R.; Wahls, R. A.

    2001-01-01

    A High Speed Civil Transport configuration was tested in the National Transonic Facility at the NASA Langley Research Center as part of NASA's High Speed Research Program. The primary purposes of the tests were to assess Reynolds number scale effects and high Reynolds number aerodynamic characteristics of a realistic, second generation supersonic transport while providing data for the assessment of computational methods. The tests included longitudinal and lateral/directional studies at transonic and low-speed, high-lift conditions across a range of Reynolds numbers from that available in conventional wind tunnels to near flight conditions. Results are presented which focus on Reynolds number and static aeroelastic sensitivities of longitudinal characteristics at Mach 0.30 for a configuration without an empennage. A fundamental change in flow-state occurred between Reynolds numbers of 30 to 40 million, which is characterized by significantly earlier inboard leading-edge separation at the high Reynolds numbers. Force and moment levels change but Reynolds number trends are consistent between the two states.

  11. Photon counting spectral CT versus conventional CT: comparative evaluation for breast imaging application

    NASA Astrophysics Data System (ADS)

    Shikhaliev, Polad M.; Fritz, Shannon G.

    2011-04-01

    Spectral CT systems with photon counting detectors have more advantages compared to conventional CT systems. However, clinical applications have been hampered for a long time due to the high demands of clinical systems and limitations of spectroscopic x-ray detectors. Photon counting detector technology has gained considerable improvements in the past decade, and spectral CT has become a hot topic. Several experimental spectral CT systems are under investigation. The purpose of this work was to perform the first direct, side-by-side comparison of existing spectral CT technology with a mature clinical CT system based on a conventional energy integrating detector. We have built an experimental spectral CT system whose main parameters are similar to the parameters of a clinical CT system. The system uses a spectroscopic cadmium zinc telluride (CZT) detector. The detector includes two rows of CZT pixels with 256 pixels in each row. The pixel size is 1 × 1 mm2, and the maximum count rate is 2 Mcounts/pixel/s. The spectral CT system has a magnification factor of 1.62 and the source to detector and source to image distances of 85 and 53 cm, respectively. The above parameters are similar to those of the clinical CT system, Siemens Sensation 16, used for comparison. The two systems were compared by imaging spatial resolution and contrast resolution phantoms made from acrylic cylinders with 14 cm diameters. The resolution phantom included Al wires with 0.3, 0.6, and 1 mm diameters, and 0.25 g cc-1 CaCO3 contrast. The contrast phantom included contrast elements with 1.7, 5, and 15 mg cc-1 iodine, and 1.1, 3.3, and 10 mg cc-1 gadolinium. The phantoms were imaged with the two systems using 120 kVp tube voltage and 470 mR total skin exposure. The spectral CT showed CT numbers, image noise, and spatial and contrast resolutions to be similar within 10% compared to the Siemens 16 system, and provided an average of 10% higher CNR. However, the spectral CT system had a major

  12. Implications of CT noise and artifacts for quantitative {sup 99m}Tc SPECT/CT imaging

    SciTech Connect

    Hulme, K. W.; Kappadath, S. C.

    2014-04-15

    Purpose: This paper evaluates the effects of computed tomography (CT) image noise and artifacts on quantitative single-photon emission computed-tomography (SPECT) imaging, with the aim of establishing an appropriate range of CT acquisition parameters for low-dose protocols with respect to accurate SPECT attenuation correction (AC). Methods: SPECT images of two geometric and one anthropomorphic phantom were reconstructed iteratively using CT scans acquired at a range of dose levels (CTDI{sub vol} = 0.4 to 46 mGy). Resultant SPECT image quality was evaluated by comparing mean signal, background noise, and artifacts to SPECT images reconstructed using the highest dose CT for AC. Noise injection was performed on linear-attenuation (μ) maps to determine the CT noise threshold for accurate AC. Results: High levels of CT noise (σ ∼ 200–400 HU) resulted in low μ-maps noise (σ ∼ 1%–3%). Noise levels greater than ∼10% in 140 keV μ-maps were required to produce visibly perceptible increases of ∼15% in {sup 99m}Tc SPECT images. These noise levels would be achieved at low CT dose levels (CTDI{sub vol} = 4 μGy) that are over 2 orders of magnitude lower than the minimum dose for diagnostic CT scanners. CT noise could also lower (bias) the expected μ values. The relative error in reconstructed SPECT signal trended linearly with the relative shift in μ. SPECT signal was, on average, underestimated in regions corresponding with beam-hardening artifacts in CT images. Any process that has the potential to change the CT number of a region by ∼100 HU (e.g., misregistration between CT images and SPECT images due to motion, the presence of contrast in CT images) could introduce errors in μ{sub 140} {sub keV} on the order of 10%, that in turn, could introduce errors on the order of ∼10% into the reconstructed {sup 99m}Tc SPECT image. Conclusions: The impact of CT noise on SPECT noise was demonstrated to be negligible for clinically achievable CT parameters. Because

  13. Ga-68-DOTATOC: Feasibility of high throughput screening by small animal PET using a clinical high-resolution PET/CT scanner

    NASA Astrophysics Data System (ADS)

    Hofmann, Michael; Weitzel, Thilo; Krause, Thomas

    2006-12-01

    As radio peptide tracers have been developed in recent years for the high sensitive detection of neuroendocrine tumors, still the broad application of other peptides to breast and prostate cancer is missing. A rapid screening of new peptides can, in theory, be based on in vivo screening in animals by PET/CT. To test this hypothesis and to asses the minimum screening time needed per animal, we used the application of Ga-68-DOTATOC PET/CT in rats as test system. The Ga-68-DOTATOC yields in a hot spot imaging with minimal background. To delineate liver and spleen, we performed PET/CT of 10 animals on a SIEMENS Biograph 16 LSO HIGHREZ after intravenous injection of 1.5 MBq Ga-68-DOTATOC per animal. Animals were mounted in an '18 slot' holding device and scanned for a single-bed position. The emission times for the PET scan was varied from 1 to 20 min. The images were assessed first for "PET only" and afterwards in PET/CT fusion mode. The detection of the two organs was good at emission times down to 1 min in PET/CT fusion mode. In the "PET only" scans, the liver was clearly to be identified down to 1 min emission in all animals. But the spleen could only be delineated only by 1 min of emission in the PET/CT-fusion mode. In conclusion the screening of "hot spot" enriching peptides is feasible. "PET only" is in terms of delineation of small organs by far inferior to PET/CT fusion. If animal tumors are above a diameter of 10 mm small, animal PET/CT using clinical high resolution scanners will enable rapid screening. Even the determination of bio-distributions becomes feasible by using list mode tools. The time for the whole survey of 18 animals including anesthesia, preparation and mounting was approximately 20 min. By use of several holding devices mounted simultaneously, a survey time of less than 1 h for 180 animals can be expected.

  14. Texture-preserved penalized weighted least-squares reconstruction of low-dose CT image via image segmentation and high-order MRF modeling

    NASA Astrophysics Data System (ADS)

    Han, Hao; Zhang, Hao; Wei, Xinzhou; Moore, William; Liang, Zhengrong

    2016-03-01

    In this paper, we proposed a low-dose computed tomography (LdCT) image reconstruction method with the help of prior knowledge learning from previous high-quality or normal-dose CT (NdCT) scans. The well-established statistical penalized weighted least squares (PWLS) algorithm was adopted for image reconstruction, where the penalty term was formulated by a texture-based Gaussian Markov random field (gMRF) model. The NdCT scan was firstly segmented into different tissue types by a feature vector quantization (FVQ) approach. Then for each tissue type, a set of tissue-specific coefficients for the gMRF penalty was statistically learnt from the NdCT image via multiple-linear regression analysis. We also proposed a scheme to adaptively select the order of gMRF model for coefficients prediction. The tissue-specific gMRF patterns learnt from the NdCT image were finally used to form an adaptive MRF penalty for the PWLS reconstruction of LdCT image. The proposed texture-adaptive PWLS image reconstruction algorithm was shown to be more effective to preserve image textures than the conventional PWLS image reconstruction algorithm, and we further demonstrated the gain of high-order MRF modeling for texture-preserved LdCT PWLS image reconstruction.

  15. High-resolution CT by diffraction-enhanced x-ray imaging: mapping of breast tissue samples and comparison with their histo-pathology.

    PubMed

    Bravin, Alberto; Keyriläinen, Jani; Fernández, Manuel; Fiedler, Stefan; Nemoz, Christian; Karjalainen-Lindsberg, Marja-Liisa; Tenhunen, Mikko; Virkkunen, Pekka; Leidenius, Marjut; von Smitten, Karl; Sipilä, Petri; Suortti, Pekka

    2007-04-21

    The aim of this study was to introduce high-resolution computed tomography (CT) of breast tumours using the diffraction-enhanced x-ray imaging (DEI) technique and to compare results with radiological and histo-pathological examinations. X-ray CT images of tumour-bearing breast tissue samples were acquired by monochromatic synchrotron radiation (SR). Due to the narrow beam and a large sample-to-detector distance scattering is rejected in the absorption contrast images (SR-CT). Large contrast enhancement is achieved by the use of the DEI-CT method, where the effects of refraction and scatter rejection are analysed by crystal optics. Clinical mammograms and CT images were recorded as reference material for a radiological examination. Three malignant and benign samples were studied in detail. Their radiographs were compared with optical images of stained histological sections. The DEI-CT images map accurately the morphology of the samples, including collagen strands and micro-calcifications of dimensions less than 0.1 mm. Histo-pathological examination and reading of the radiographs were done independently, and the conclusions were in general agreement. High-resolution DEI-CT images show strong contrast and permit visualization of details invisible in clinical radiographs. The radiation dose may be reduced by an order of magnitude without compromising image quality, which would make possible clinical in vivo DEI-CT with future compact SR sources. PMID:17404464

  16. An investigation of small scales of turbulence in a boundary layer at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Wallace, James M.; Ong, L.; Balint, J.-L.

    1993-01-01

    The assumption that turbulence at large wave-numbers is isotropic and has universal spectral characteristics which are independent of the flow geometry, at least for high Reynolds numbers, has been a cornerstone of closure theories as well as of the most promising recent development in the effort to predict turbulent flows, viz. large eddy simulations. This hypothesis was first advanced by Kolmogorov based on the supposition that turbulent kinetic energy cascades down the scales (up the wave-numbers) of turbulence and that, if the number of these cascade steps is sufficiently large (i.e. the wave-number range is large), then the effects of anisotropies at the large scales are lost in the energy transfer process. Experimental attempts were repeatedly made to verify this fundamental assumption. However, Van Atta has recently suggested that an examination of the scalar and velocity gradient fields is necessary to definitively verify this hypothesis or prove it to be unfounded. Of course, this must be carried out in a flow with a sufficiently high Reynolds number to provide the necessary separation of scales in order unambiguously to provide the possibility of local isotropy at large wave-numbers. An opportunity to use our 12-sensor hot-wire probe to address this issue directly was made available at the 80'x120' wind tunnel at the NASA Ames Research Center, which is normally used for full-scale aircraft tests. An initial report on this high Reynolds number experiment and progress toward its evaluation is presented.

  17. High Reynolds number and turbulence effects on aerodynamics and heat transfer in a turbine cascade

    NASA Technical Reports Server (NTRS)

    Yeh, Frederick C.; Hippensteele, Steven A.; Vanfossen, G. James; Poinsatte, Philip E.; Ameri, Ali

    1993-01-01

    Experimental data on pressure distribution and heat transfer on a turbine airfoil were obtained over a range of Reynolds numbers from 0.75 to 7.5 x 10 exp 6 and a range of turbulence intensities from 1.8 to about 15 percent. The purpose of this study was to obtain fundamental heat transfer and pressure distribution data over a wide range of high Reynolds numbers and to extend the heat transfer data base to include the range of Reynolds numbers encountered in the Space Shuttle main engine (SSME) turbopump turbines. Specifically, the study aimed to determine (1) the effect of Reynolds number on heat transfer, (2) the effect of upstream turbulence on heat transfer and pressure distribution, and (3) the relationship between heat transfer at high Reynolds numbers and the current data base. The results of this study indicated that Reynolds number and turbulence intensity have a large effect on both the transition from laminar to turbulent flow and the resulting heat transfer. For a given turbulence intensity, heat transfer for all Reynolds numbers at the leading edge can be correlated with the Frossling number developed for lower Reynolds numbers. For a given turbulence intensity, heat transfer for the airfoil surfaces downstream of the leading edge can be approximately correlated with a dimensionless parameter. Comparison of the experimental results were also made with a numerical solution from a two-dimensional Navier-Stokes code.

  18. A potential strategy for high-grade gliomas: combination treatment with lithium chloride and BmK CT.

    PubMed

    Fu, Yuejun; Zheng, Shuhua; Huang, Rui; An, Na; Zheng, Yali; Zhang, Zhiyun; Liang, Aihua

    2012-01-01

    Therapies for high-grade gliomas (HHG) that have strong tendency of infiltration and resistance to chemotherapies are currently unavailable. Here, we report that lower-dose combination therapy of Buthus martensii Karsch (BmK) CT, a type of scorpion toxin peptide, and LiCl, clinically used as mood stabilizer, could synergistically inhibit the migration, invasion and proliferation of C6 glioma cells. The decreased invasiveness of C6 glioma cells was accompanied by inhibited activation, catalytic activity and/or expression of matrix metalloproteinase-2. Moreover, TOPfalsh luciferase reporter and immunofluorescence staining showed altered localization pattern of β-catenin at the leading edge of 2D scratch. Our results suggested that the combination treatment of lithium and BmK CT may constitute a novel and potential strategy for HHG therapy. PMID:21932030

  19. Micro-CT scan reveals an unexpected high-volume and interconnected pore network in a Cretaceous Sanagasta dinosaur eggshell.

    PubMed

    Hechenleitner, E Martín; Grellet-Tinner, Gerald; Foley, Matthew; Fiorelli, Lucas E; Thompson, Michael B

    2016-03-01

    The Cretaceous Sanagasta neosauropod nesting site (La Rioja, Argentina) was the first confirmed instance of extinct dinosaurs using geothermal-generated heat to incubate their eggs. The nesting strategy and hydrothermal activities at this site led to the conclusion that the surprisingly 7 mm thick-shelled eggs were adapted to harsh hydrothermal microenvironments. We used micro-CT scans in this study to obtain the first three-dimensional microcharacterization of these eggshells. Micro-CT-based analyses provide a robust assessment of gas conductance in fossil dinosaur eggshells with complex pore canal systems, allowing calculation, for the first time, of the shell conductance through its thickness. This novel approach suggests that the shell conductance could have risen during incubation to seven times more than previously estimated as the eggshell erodes. In addition, micro-CT observations reveal that the constant widening and branching of pore canals form a complex funnel-like pore canal system. Furthermore, the high density of pore canals and the presence of a lateral canal network in the shell reduce the risks of pore obstruction during the extended incubation of these eggs in a relatively highly humid and muddy nesting environment. PMID:27009182

  20. CT -- Body

    MedlinePlus

    ... News Physician Resources Professions Site Index A-Z Computed Tomography (CT) - Body Computed tomography (CT) of the body uses special x-ray ... Body? What is CT Scanning of the Body? Computed tomography, more commonly known as a CT or CAT ...

  1. Imaging of pore networks and related interfaces in soil systems by using high resolution X-ray micro-CT

    NASA Astrophysics Data System (ADS)

    Zacher, Gerhard; Eickhorst, Thilo; Schmidt, Hannes; Halisch, Matthias

    2016-04-01

    Today's high-resolution X-ray CT with its powerful tubes and great detail detectability lends itself naturally to geological and pedological applications. Those include the non-destructive interior examination and textural analysis of rock and soil samples and their permeability and porosity - to name only a few. Especially spatial distribution and geometry of pores, mineral phases and fractures are important for the evaluation of hydrologic and aeration properties in soils as well as for root development in the soil matrix. The possibility to visualize a whole soil aggregate or root tissue in a non-destructive way is undoubtedly the most valuable feature of this type of analysis and is a new area for routine application of high resolution X-ray micro-CT. The paper outlines recent developments in hard- and software requirements for high resolution CT. It highlights several pedological applications which were performed with the phoenix nanotom m, the first 180 kV nanofocus CT system tailored specifically for extremely high-resolution scans of variable sized samples with voxel-resolutions down to < 300 nm. In addition very good contrast resolution can be obtained as well which is necessary to distinguish biogenic material in soil aggregates amongst others. We will address visualization and quantification of porous networks in 3D in different environmental samples ranging from clastic sedimentary rock to soil cores and individual soil aggregates. As several processes and habitat functions are related to various pore sizes imaging of the intact soil matrix will be presented on different scales of interest - from the mm-scale representing the connectivity of macro-pores down to the micro-scale representing the space of microbial habitats. Therefore, soils were impregnated with resin and scanned via X-ray CT. Scans at higher resolution were obtained from sub-volumes cut from the entire resin impregnated block and from crop roots surrounded by rhizosphere soil. Within the

  2. The Building Blocks of High School Redesign. Info Brief. Number 49

    ERIC Educational Resources Information Center

    Ewing, Tom

    2007-01-01

    U.S. high schools are, with a number of notable exceptions, failing to prepare students adequately for futures as well-equipped and productive contributors to our society, whether as college students or as members of the workplace. This "Infobrief" focuses on three key elements of high school redesign proposed by Association for Supervision and…

  3. Multigrid solution of the convection-diffusion equation with high-Reynolds number

    SciTech Connect

    Zhang, Jun

    1996-12-31

    A fourth-order compact finite difference scheme is employed with the multigrid technique to solve the variable coefficient convection-diffusion equation with high-Reynolds number. Scaled inter-grid transfer operators and potential on vectorization and parallelization are discussed. The high-order multigrid method is unconditionally stable and produces solution of 4th-order accuracy. Numerical experiments are included.

  4. Spectroscopic diagnostics of superthermal electrons with high-number harmonic EC radiation in tokamak reactor plasmas

    NASA Astrophysics Data System (ADS)

    Minashin, P. V.; Kukushkin, A. B.

    2015-03-01

    A method of spectroscopic diagnostics of the average perpendicular-to-magnetic-field momentum of the superthermal component of the electron velocity distribution (EVD), based on the high-number-harmonic electron cyclotron (EC) radiation, is suggested for nuclear fusion-reactor plasmas under condition of a strong auxiliary heating (e.g. in tokamak DEMO, a next step after tokamak ITER). The method is based on solving an inverse problem for reconstruction of the EVD in parallel and perpendicular-to-magnetic-field components of electron momentum at high and moderate energies responsible for the emission of the high-number-harmonic EC radiation.

  5. High-resolution secondary reconstructions with the use of flat panel CT in the clinical assessment of patients with cochlear implants.

    PubMed

    Pearl, M S; Roy, A; Limb, C J

    2014-06-01

    Radiologic assessment of cochlear implants can be limited because of metallic streak artifacts and the high attenuation of the temporal bones. We report on 14 patients with 18 cochlear implants (17 Med-El standard 31.5-mm arrays, 1 Med-El medium 24-mm array) who underwent flat panel CT with the use of high-resolution secondary reconstruction techniques. Flat panel CT depicted the insertion site, cochlear implant course, and all 216 individual electrode contacts. The calculated mean angular insertion depth for standard arrays was 591.9° (SD = 70.9; range, 280°). High-resolution secondary reconstructions of the initial flat panel CT dataset, by use of a manually generated field of view, Hounsfield unit kernel type, and sharp image characteristics, provided high-quality images with improved spatial resolution. Flat panel CT is a promising imaging tool for the postoperative evaluation of cochlear implant placement. PMID:24371026

  6. High Stakes Testing and High School Completion. NBETPP Statements, Volume 1, Number 3.

    ERIC Educational Resources Information Center

    Clarke, Marguerite; Haney, Walter; Madaus, George

    This report examines how high stakes assessments affect dropout and high school completion rates. The focus is on five suggestive lines of evidence about this relationship. This evidence is drawn in part from studies done at Boston College or by researchers for the National Board on Educational Testing and Public Policy. The conclusion drawn is…

  7. Performance evaluation of the General Electric eXplore CT 120 micro-CT using the vmCT phantom

    NASA Astrophysics Data System (ADS)

    Bahri, M. A.; Warnock, G.; Plenevaux, A.; Choquet, P.; Constantinesco, A.; Salmon, E.; Luxen, A.; Seret, A.

    2011-08-01

    The eXplore CT 120 is the latest generation micro-CT from General Electric. It is equipped with a high-power tube and a flat-panel detector. It allows high resolution and high contrast fast CT scanning of small animals. The aim of this study was to compare the performance of the eXplore CT 120 with that of the eXplore Ultra, its predecessor for which the methodology using the vmCT phantom has already been described [1].The phantom was imaged using typical a rat (fast scan or F) or mouse (in vivo bone scan or H) scanning protocols. With the slanted edge method, a 10% modulation transfer function (MTF) was observed at 4.4 (F) and 3.9-4.4 (H) mm-1 corresponding to 114 μm resolution. A fairly larger MTF was obtained by the coil method with the MTF for the thinnest coil (3.3 mm-1) equal to 0.32 (F) and 0.34 (H). The geometric accuracy was better than 0.3%. There was a highly linear (R2>0.999) relationship between measured and expected CT numbers for both the CT number accuracy and linearity sections of the phantom. A cupping effect was clearly seen on the uniform slices and the uniformity-to-noise ratio ranged from 0.52 (F) to 0.89 (H). The air CT number depended on the amount of polycarbonate surrounding the area where it was measured; a difference as high as approximately 200 HU was observed. This hindered the calibration of this scanner in HU. This is likely due to the absence of corrections for beam hardening and scatter in the reconstruction software. However in view of the high linearity of the system, the implementation of these corrections would allow a good quality calibration of the scanner in HU. In conclusion, the eXplore CT 120 achieved a better spatial resolution than the eXplore Ultra (based on previously reported specifications) and future software developments will include beam hardening and scatter corrections that will make the new generation CT scanner even more promising.

  8. Statistical Analysis of Yarn Feature Parameters in C/Epoxy Plain-Weave Composite Using Micro CT with High-Resolution Lens-Coupled Detector

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Wang, Zhong-wei

    2016-08-01

    C/Epoxy plain-weave composite is difficult to clear imaging in Micro CT with flat panel detector due to the similar atomic numbers of component materials. To solve this problem, a new Micro CT equipment with high-resolution lens-coupled detector is used to reconstruct 3D images of C/Epoxy. Slice data correction with ellipse projection is used to acquire real yarn normal cross-section information. A reference period method suitable for plain-weave composite is then detailed to evaluate statistical properties of yarn feature parameters. In the process of determination of real extreme slices, dislocation phenomenon existed in the laminated composite is discovered. Several possible reasons caused this phenomenon are discussed. Systematic trends, standard deviations and correlation lengths of stochastic deviations with original and corrected data are evaluated respectively by the application of reference period method. The statistical results show that mean out-of-plane yarn waviness, semi-axes, cross-section area and aspect ratio exhibit periodic characteristics, and the maximum effect of slice data correction on all statistical properties of feature parameters is twist angle.

  9. Statistical Analysis of Yarn Feature Parameters in C/Epoxy Plain-Weave Composite Using Micro CT with High-Resolution Lens-Coupled Detector

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Wang, Zhong-wei

    2016-02-01

    C/Epoxy plain-weave composite is difficult to clear imaging in Micro CT with flat panel detector due to the similar atomic numbers of component materials. To solve this problem, a new Micro CT equipment with high-resolution lens-coupled detector is used to reconstruct 3D images of C/Epoxy. Slice data correction with ellipse projection is used to acquire real yarn normal cross-section information. A reference period method suitable for plain-weave composite is then detailed to evaluate statistical properties of yarn feature parameters. In the process of determination of real extreme slices, dislocation phenomenon existed in the laminated composite is discovered. Several possible reasons caused this phenomenon are discussed. Systematic trends, standard deviations and correlation lengths of stochastic deviations with original and corrected data are evaluated respectively by the application of reference period method. The statistical results show that mean out-of-plane yarn waviness, semi-axes, cross-section area and aspect ratio exhibit periodic characteristics, and the maximum effect of slice data correction on all statistical properties of feature parameters is twist angle.

  10. Wind tunnel tests of two airfoils for wind turbines operating at high reynolds numbers

    SciTech Connect

    Sommers, D.; Tangler, J.

    2000-06-29

    The objectives of this study were to verify the predictions of the Eppler Airfoil Design and Analysis Code for Reynolds numbers up to 6 x 106 and to acquire the section characteristics of two airfoils being considered for large, megawatt-size wind turbines. One airfoil, the S825, was designed to achieve a high maximum lift coefficient suitable for variable-speed machines. The other airfoil, the S827, was designed to achieve a low maximum lift coefficient suitable for stall-regulated machines. Both airfoils were tested in the NASA Langley Low-Turbulence Pressure Tunnel (LTPT) for smooth, fixed-transition, and rough surface conditions at Reynolds numbers of 1, 2, 3, 4, and 6 x 106. The results show the maximum lift coefficient of both airfoils is substantially underpredicted for Reynolds numbers over 3 x 106 and emphasized the difficulty of designing low-lift airfoils for high Reynolds numbers.

  11. Wall-modeling for large-eddy simulation of high Reynolds number supersonic flows

    NASA Astrophysics Data System (ADS)

    Kawai, Soshi; Larsson, Johan; Lele, Sanjiva

    2010-11-01

    We present an idea of approximate wall-boundary-condition approach with dynamic procedure for large-eddy simulation of Mach 3 supersonic turbulent boundary layer at various Reynolds numbers (Reδ=2 x10^4, 10^5 and 10^6) on a flat plate. This wall-model is the extension of previous work by Wang and Moin [Phys. Fluid, 14, 2043 (2002)] for incompressible flows to compressible flows. We note that the present study is both the first extension of the dynamic concept to compressible flows and also the first test at high Reynolds number flows. The present study also revisits the issue of numerical errors near wall-region on outer-layer coarse LES mesh. The numerical results are compared with wall-resolved LES data (at low Reynolds number case) and available experimental data (at high Reynolds number case).

  12. Active Control of Flow Separation on a High-Lift System with Slotted Flap at High Reynolds Number

    NASA Technical Reports Server (NTRS)

    Khodadoust, Abdollah; Washburn, Anthony

    2007-01-01

    The NASA Energy Efficient Transport (EET) airfoil was tested at NASA Langley's Low- Turbulence Pressure Tunnel (LTPT) to assess the effectiveness of distributed Active Flow Control (AFC) concepts on a high-lift system at flight scale Reynolds numbers for a medium-sized transport. The test results indicate presence of strong Reynolds number effects on the high-lift system with the AFC operational, implying the importance of flight-scale testing for implementation of such systems during design of future flight vehicles with AFC. This paper describes the wind tunnel test results obtained at the LTPT for the EET high-lift system for various AFC concepts examined on this airfoil.

  13. Optimization of an Advanced Design Three-Element Airfoil at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Lin, John C.; Dominik, Chet J.

    1995-01-01

    New high-lift components have been designed for a three-element advanced high-lift research airfoil using a state-of-the-art computational method. The new components were designed with the aim to provide high maximum-lift values while maintaining attached flow on the single-segment flap at approach conditions. This three-element airfoil has been tested in the NASA Langley Low-Turbulence Pressure Tunnel at chord Reynolds number up to 16 million. The performance of the NASA research airfoil is compared to a reference advanced high-lift research airfoil. Effects of Reynolds number on slat and flap rigging have been studied experimentally. The performance trend of this new high-lift design is comparable to that predicted by the computational method over much of the angle of attack range. Nevertheless, the method did not accurately predict the airfoil performance or the configuration-based trends near maximum lift.

  14. SU-E-I-04: Improving CT Quality for Radiation Therapy of Patients with High Body Mass Index Using Iterative Reconstruction Algorithms

    SciTech Connect

    Noid, G; Tai, A; Li, X

    2015-06-15

    Purpose: Iterative reconstruction (IR) algorithms are developed to improve CT image quality (IQ) by reducing noise without diminishing spatial resolution or contrast. The CT IQ for patients with a high Body Mass Index (BMI) can suffer from increased noise due to photon starvation. The purpose of this study is to investigate and to quantify the IQ enhancement for high BMI patients through the application of IR algorithms. Methods: CT raw data collected for 6 radiotherapy (RT) patients with BMI, greater than or equal to 30 were retrospectively analyzed. All CT data were acquired using a CT scanner (Somaton Definition AS Open, Siemens) installed in a linac room (CT-on-rails) using standard imaging protocols. The CT data were reconstructed using the Sinogram Affirmed Iterative Reconstruction (SAFIRE) and Filtered Back Projection (FBP) methods. IQ metrics of the obtained CTs were compared and correlated with patient depth and BMI. The patient depth was defined as the largest distance from anterior to posterior along the bilateral symmetry axis. Results: IR techniques are demonstrated to preserve contrast and reduce noise in comparison to traditional FBP. Driven by the reduction in noise, the contrast to noise ratio is roughly doubled by adopting the highest SAFIRE strength. A significant correlation was observed between patient depth and IR noise reduction through Pearson’s correlation test (R = 0.9429/P = 0.0167). The mean patient depth was 30.4 cm and the average relative noise reduction for the strongest iterative reconstruction was 55%. Conclusion: The IR techniques produce a measureable enhancement to CT IQ by reducing the noise. Dramatic noise reduction is evident for the high BMI patients. The improved CT IQ enables more accurate delineation of tumors and organs at risk and more accuarte dose calculations for RT planning and delivery guidance. Supported by Siemens.

  15. Numerical and approximate solution of the high Reynolds number small separation problem

    NASA Technical Reports Server (NTRS)

    Davis, R. T.

    1976-01-01

    Several possible methods of solving the small separation problem at high Reynolds number are investigated. In addition to using analytical methods, there are several numerical approaches which are used. High Reynolds number laminar two dimensional problems are used for simplicity. A brief discussion is given of the finite difference methods since these methods are discussed in detail. Most of the emphasis is placed on developing an approximate integral method. As a model problem the supersonic compression ramp problem is chosen since several numerical solutions along with experimental data are available. The techniques discussed are modified and applied to other similar type wall geometries.

  16. Qualification of a Method to Calculate the Irrecoverable Pressure Loss in High Reynolds Number Piping Systems

    SciTech Connect

    Sigg, K. C.; Coffield, R. D.

    2002-09-01

    High Reynolds number test data has recently been reported for both single and multiple piping elbow design configurations at earlier ASME Fluid Engineering Division conferences. The data of these studies ranged up to a Reynolds number of 42 x 10[sup]6 which is significantly greater than that used to establish design correlations before the data was available. Many of the accepted design correlations, based on the lower Reynolds number data, date back as much as fifty years. The new data shows that these earlier correlations are extremely conservative for high Reynolds number applications. Based on the recent high Reynolds number information a new recommended method has been developed for calculating irrecoverable pressure loses in piping systems for design considerations such as establishing pump sizing requirements. This paper describes the recommended design approach and additional testing that has been performed as part of the qualification of the method. This qualification testing determined the irrecoverable pressure loss of a piping configuration that would typify a limiting piping section in a complicated piping network, i.e., multiple, tightly coupled, out-of-plane elbows in series under high Reynolds number flow conditions. The overall pressure loss measurements were then compared to predictions, which used the new methodology to assure that conservative estimates for the pressure loss (of the type used for pump sizing) were obtained. The recommended design methodology, the qualification testing and the comparison between the predictions and the test data are presented. A major conclusion of this study is that the recommended method for calculating irrecoverable pressure loss in piping systems is conservative yet significantly lower than predicted by early design correlations that were based on the extrapolation of low Reynolds number test data.

  17. A high order accurate finite element algorithm for high Reynolds number flow prediction

    NASA Technical Reports Server (NTRS)

    Baker, A. J.

    1978-01-01

    A Galerkin-weighted residuals formulation is employed to establish an implicit finite element solution algorithm for generally nonlinear initial-boundary value problems. Solution accuracy, and convergence rate with discretization refinement, are quantized in several error norms, by a systematic study of numerical solutions to several nonlinear parabolic and a hyperbolic partial differential equation characteristic of the equations governing fluid flows. Solutions are generated using selective linear, quadratic and cubic basis functions. Richardson extrapolation is employed to generate a higher-order accurate solution to facilitate isolation of truncation error in all norms. Extension of the mathematical theory underlying accuracy and convergence concepts for linear elliptic equations is predicted for equations characteristic of laminar and turbulent fluid flows at nonmodest Reynolds number. The nondiagonal initial-value matrix structure introduced by the finite element theory is determined intrinsic to improved solution accuracy and convergence. A factored Jacobian iteration algorithm is derived and evaluated to yield a consequential reduction in both computer storage and execution CPU requirements while retaining solution accuracy.

  18. Estimating copy numbers of alleles from population-scale high-throughput sequencing data

    PubMed Central

    2015-01-01

    Background With the recent development of microarray and high-throughput sequencing (HTS) technologies, a number of studies have revealed catalogs of copy number variants (CNVs) and their association with phenotypes and complex traits. In parallel, a number of approaches to predict CNV regions and genotypes are proposed for both microarray and HTS data. However, only a few approaches focus on haplotyping of CNV loci. Results We propose a novel approach to infer copy unit alleles and their numbers in each sample simultaneously from population-scale HTS data by variational Bayesian inference on a generative probabilistic model inspired by latent Dirichlet allocation, which is a well studied model for document classification problems. In simulation studies, we evaluated concordance between inferred and true copy unit alleles for lower-, middle-, and higher-copy number dataset, in which precision and recall were ≥ 0.9 for data with mean coverage ≥ 10× per copy unit. We also applied the approach to HTS data of 1123 samples at highly variable salivary amylase gene locus and a pseudogene locus, and confirmed consistency of the estimated alleles within samples belonging to a trio of CEPH/Utah pedigree 1463 with 11 offspring. Conclusions Our proposed approach enables detailed analysis of copy number variations, such as association study between copy unit alleles and phenotypes or biological features including human diseases. PMID:25707811

  19. High-order lattice Boltzmann models for wall-bounded flows at finite Knudsen numbers

    NASA Astrophysics Data System (ADS)

    Feuchter, C.; Schleifenbaum, W.

    2016-07-01

    We analyze a large number of high-order discrete velocity models for solving the Boltzmann-Bhatnagar-Gross-Krook equation for finite Knudsen number flows. Using the Chapman-Enskog formalism, we prove for isothermal flows a relation identifying the resolved flow regimes for low Mach numbers. Although high-order lattice Boltzmann models recover flow regimes beyond the Navier-Stokes level, we observe for several models significant deviations from reference results. We found this to be caused by their inability to recover the Maxwell boundary condition exactly. By using supplementary conditions for the gas-surface interaction it is shown how to systematically generate discrete velocity models of any order with the inherent ability to fulfill the diffuse Maxwell boundary condition accurately. Both high-order quadratures and an exact representation of the boundary condition turn out to be crucial for achieving reliable results. For Poiseuille flow, we can reproduce the mass flow and slip velocity up to the Knudsen number of 1. Moreover, for small Knudsen numbers, the Knudsen layer behavior is recovered.

  20. A Study of Hypersonic Compression-Corner Flow at High Reynolds Numbers

    NASA Astrophysics Data System (ADS)

    Vetlutsky, V. N.; Ganimedov, V. L.

    2002-07-01

    To numerically solve the problem for the ramp flow at high Reynolds number, it is justified to use the classical Prandtl model and to part the flow into an inviscid region and a thin boundary layer. This model is based on a rigorous asymptotic theory and describes the flow the more accurately, the higher the Reynolds number is. Since a flow separation in a compression corner may occur, the present work deals with unsteady boundary-layer equations. The approximation error in discretization of boundary-layer equations is always smaller than the value of viscid terms since the Reynolds number can be eliminated from the equations by a suitable substitution of variables. Besides, the requirement for the sufficient number of points in the cross-flow direction can be fulfilled in the case of middle-class computers since the solution is being built in a narrow near-wall region.

  1. A review of some Reynolds number effects related to bodies at high angles of attack

    NASA Technical Reports Server (NTRS)

    Polhamus, E. C.

    1984-01-01

    A review of some effects of Reynolds number on selected aerodynamic characteristics of two- and three-dimensional bodies of various cross sections in relation to fuselages at high angles of attack at subsonic and transonic speeds is presented. Emphasis is placed on the Reynolds number ranges above the subcritical and angles of attack where lee side vortex flow or unsteady wake type flows predominate. Lists of references, arranged in subject categories, are presented with emphasis on those which include data over a reasonable Reynolds number range. Selected Reynolds number data representative of various aerodynamic flows around bodies are presented and analyzed and some effects of these flows on fuselage aerodynamic parameters are discussed.

  2. Effect of High Shock Number on Acute Complication Development After Extracorporeal Shockwave Lithotripsy

    PubMed Central

    Hadj-Moussa, Miriam

    2013-01-01

    Abstract Purpose We assessed whether high shock number is associated with higher rates of acute complication development after extracorporeal shockwave lithotripsy (SWL). Patients and Methods A retrospective chart review of 372 patients who underwent 436 SWL procedures at 24 kV using a Medstone STS-T lithotripter (Medstone International Inc., Aliso Viejo, CA) was conducted. Complications occurred within 4 weeks of SWL. Treatments were split into three cohorts based on shock number (<2400, 2401–4000, and >4000). Postoperative sequelae of patients who were stone free and those with residual stone were studied separately. Chi-square tests were used to evaluate the relationship between shock number cohort and postoperative complication development. Results SWL treatments recorded for each cohort were 158 (37.4%), 145 (34.4%), and 119 (28.2%), respectively. The short-term complication rate when SWL was successful was 8.3% overall. Complication rate for each cohort was 9.5% (11), 7.8% (5), and 7.2% (7), respectively. When SWL was successful, statistical analysis revealed no significant difference between complication rates and shock number cohort (P=0.63). Complications in patients with a residual stone occurred after 41.4% of treatments and trended upward with shock number cohort, but did not reach statistical significance (P=0.84). Conclusions At high voltage, high shock number was not shown to cause higher rates of short-term postoperative complications, as experienced by patients, when SWL was successful or resulted in a residual stone, yet complication rates associated with residual stone burden were approximately five times as common. Forgoing a higher shock number in the presence of a residual stone may therefore increase the risks of sequelae immediately after SWL. PMID:23537270

  3. Transition Documentation on a Three-Element High-Lift Configuration at High Reynolds Numbers: Analysis

    NASA Technical Reports Server (NTRS)

    Bertelrud, Arild; Anders, J. B. (Technical Monitor)

    2002-01-01

    A 2-D high-lift system experiment was conducted in August of 1996 in the Low Turbulence Pressure Tunnel at NASA Langley Research Center, Hampton, VA. The purpose of the experiment was to obtain transition measurements on a three element high-lift system for CFD code validation studies. A transition database has been created using the data from this experiment. The present report contains the analysis of the surface hot film data in terms of the transition locations on the three elements. It also includes relevant information regarding the pressure loads and distributions and the wakes behind the model to aid in the interpretation of the transition data. For some of the configurations the current pressure data has been compared with previous wind tunnel entries of the same model. The methodology used to determine the regions of transitional flow is outlined and each configuration tested has been analyzed. A discussion of interference effects, repeatability, and three-dimensional effects on the data is included.

  4. Development of a new correlation to calculate permeability for flows with high Knudsen number

    NASA Astrophysics Data System (ADS)

    Esmaeil, Dehdashti

    2016-02-01

    Flows with high Knudsen number play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow with high Knudsen number using modified lattice Boltzmann method (LBM) through a porous medium in a channel. The effect of collision between molecules and solid walls, which is required to accurately simulate transition flow regime, is taken into account using a modified relaxation time. Slip velocity on the wall, which is another significant difficulty in simulating transition flow regime, is captured using the slip reflection boundary condition (SRBC). The geometry of porous medium is considered as in-line and staggered. The results are in good agreement with previous works. A new correlation is obtained between permeability, Knudsen number and porosity for flows in transition flow regimes.

  5. Use of CT in detection of internal damage and repair and determination of authenticity in high-quality bowed stringed instruments.

    PubMed

    Sirr, S A; Waddle, J R

    1999-01-01

    Computed tomography (CT) was used to evaluate 17 high-quality violins and cellos crafted between 1633 and 1872 by master craftsmen such as Guarneri, Amati, and Stradivari. Multiple high-resolution CT scans were obtained in each instrument, and additional scans were obtained when defects or repair was detected. Varying degrees of internal damage (eg, wormholes, air gaps, plastic deformities of wood) or repair (eg, glue lines, filler material, wooden cleats and patches) not seen at visual inspection were detected in all 17 instruments. In addition, CT allowed noninvasive identification of the internal wood grain pattern unique to each instrument, thereby facilitating verification of authenticity to help protect against loss, theft, or forgery. The information provided by CT analysis of valuable bowed stringed instruments may prove useful to prospective buyers or to insurance companies that specialize in insuring such instruments against accidental loss or damage. PMID:10336193

  6. A RAPID METHOD FOR PRODUCTION OF HIGH NUMBERS OF PURIFIED CRYPTOSPORIDIUM PARVUM OOCYSTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most procedures that have been described for purifying Cryptosporidium parvum oocysts are designed to either identify the parasites in clinical specimens or isolate oocysts from a small volume of feces from infected animals. The present study describes a rapid method for purifying high numbers of C...

  7. The George C. Marshall Space Flight Center High Reynolds Number Wind Tunnel Technical Handbook

    NASA Technical Reports Server (NTRS)

    Gwin, H. S.

    1975-01-01

    The High Reynolds Number Wind Tunnel at the George C. Marshall Space Flight Center is described. The following items are presented to illustrate the operation and capabilities of the facility: facility descriptions and specifications, operational and performance characteristics, model design criteria, instrumentation and data recording equipment, data processing and presentation, and preliminary test information required.

  8. Application of Magnetic Suspension and Balance Systems to Ultra-High Reynolds Number Facilities

    NASA Technical Reports Server (NTRS)

    Britcher, Colin P.

    1996-01-01

    The current status of wind tunnel magnetic suspension and balance system development is briefly reviewed. Technical work currently underway at NASA Langley Research Center is detailed, where it relates to the ultra-high Reynolds number application. The application itself is addressed, concluded to be quite feasible, and broad design recommendations given.

  9. Dynamics of high Weber number drops impacting on hydrophobic surfaces with closed micro-cells.

    PubMed

    Zhang, Rui; Hao, Pengfei; Zhang, Xiwen; He, Feng

    2016-06-29

    The impact dynamics and bouncing performance of high Weber number drops on hydrophobic surfaces with open and closed micro-cells are investigated. Central wetted rings are observed on both closed-cell and open-cell surfaces under high Weber number collisions, which are proposed to constitute the key element affecting the bouncing behaviour. It is found that the drops rebound on closed-cell surfaces where the central area is in the "hybrid wetting state" at high Weber numbers, while the drops adhere to the open-cell surfaces where the central region is in the Wenzel state. A theoretical model is developed to explain this interesting phenomenon, in which the liquid cannot reach the bottom of the closed-cell hydrophobic surfaces since the air stored in micro-cavities prevents the sliding motion of the liquid film and functions as a "gas spring" lifting the liquid lamella. This indicates that the hydrophobic surface with simple micro cavities can maintain the water-repellent characteristics under drop impacts at high Weber numbers. These findings are expected to be crucial to a fundamental understanding of the rapid collisions between drops and micro-structured surfaces, as well as a valuable strategy to guide the fabrication of novel super water-repellant and anti-icing surfaces. PMID:27306824

  10. Turbulence Model Comparisons and Reynolds Number Effects Over a High-Speed Aircraft at Transonic Speeds

    NASA Technical Reports Server (NTRS)

    Rivers, Melissa B.; Wahls, Richard A.

    1999-01-01

    This paper gives the results of a grid study, a turbulence model study, and a Reynolds number effect study for transonic flows over a high-speed aircraft using the thin-layer, upwind, Navier-Stokes CFL3D code. The four turbulence models evaluated are the algebraic Baldwin-Lomax model with the Degani-Schiff modifications, the one-equation Baldwin-Barth model, the one-equation Spalart-Allmaras model, and Menter's two-equation Shear-Stress-Transport (SST) model. The flow conditions, which correspond to tests performed in the NASA Langley National Transonic Facility (NTF), are a Mach number of 0.90 and a Reynolds number of 30 million based on chord for a range of angle-of-attacks (1 degree to 10 degrees). For the Reynolds number effect study, Reynolds numbers of 10 and 80 million based on chord were also evaluated. Computed forces and surface pressures compare reasonably well with the experimental data for all four of the turbulence models. The Baldwin-Lomax model with the Degani-Schiff modifications and the one-equation Baldwin-Barth model show the best agreement with experiment overall. The Reynolds number effects are evaluated using the Baldwin-Lomax with the Degani-Schiff modifications and the Baldwin-Barth turbulence models. Five angles-of-attack were evaluated for the Reynolds number effect study at three different Reynolds numbers. More work is needed to determine the ability of CFL3D to accurately predict Reynolds number effects.

  11. CT Scans

    MedlinePlus

    ... cross-sectional pictures of your body. Doctors use CT scans to look for Broken bones Cancers Blood clots Signs of heart disease Internal bleeding During a CT scan, you lie still on a table. The table ...

  12. Focus on new perspectives in high-Rayleigh-number turbulent convection Focus on new perspectives in high-Rayleigh-number turbulent convection

    NASA Astrophysics Data System (ADS)

    Schumacher, Jörg; Bodenschatz, Eberhard

    2012-09-01

    Thermal convection in a gravitational field is the source of most large-scale flows on Earth, planets and stars. It is also used to heat houses or to cool passively with metal vanes, as for example in most electronic equipment. The driving force for thermal convection is buoyancy. When a fluid is heated it expands, i.e., it changes its mass density. If the fluid in a gravitational field and heating is applied in such a way that cold, dense fluid is on top of that which is warmer and lighter, the warm fluid will rise when the driving forces of buoyancy overcome viscous drag and thermal diffusion. The experimentally best defined and most studied example is Rayleigh-Bénard convection (RBC), where a horizontal fluid layer is heated from below and cooled from above. For an incompressible fluid and Boussinesq conditions, where due to modest temperature gradients only the linear temperature dependence of density governs the physics, two dimensionless parameters describe the physics. One is the Rayleigh number, Ra, which is proportional to the temperature difference across the fluid layer of thickness, d, and to d3, implying that high Ra can be achieved experimentally at modest temperature differences only with a large d. The other parameter is the Prandtl number, Pr, which describes the relative importance of the convective nonlinearities in the momentum and heat equations. The geometry and thermal boundary conditions of the experimental apparatus are other important factors. Experiments usually strive to realize the theoretically most easily studied boundary conditions, i.e. perfectly conducting top and bottom plates and insulating sidewalls. As mentioned above, situations with large Ra require large cell heights. In experiments, typical geometries chosen are mostly cylindrical, with aspect ratios Γ = diameter/height between 1/4 and 2. For RBC, the onset of convection in an infinitely extended layer between no-slip walls is independent of the Prandtl number and occurs

  13. Dose management in CT facility

    PubMed Central

    Tsapaki, V; Rehani, M

    2007-01-01

    Computed Tomography (CT) examinations have rapidly increased in number over the last few years due to recent advances such as the spiral, multidetector-row, CT fluoroscopy and Positron Emission Tomography (PET)-CT technology. This has resulted in a large increase in collective radiation dose as reported by many international organisations. It is also stated that frequently, image quality in CT exceeds the level required for confident diagnosis. This inevitably results in patient radiation doses that are higher than actually required, as also stressed by the US Food and Drug Administration (FDA) regarding the CT exposure of paediatric and small adult patients. However, the wide range in exposure parameters reported, as well as the different CT applications reveal the difficulty in standardising CT procedures. The purpose of this paper is to review the basic CT principles, outline the recent technological advances and their impact in patient radiation dose and finally suggest methods of radiation dose optimisation. PMID:21614279

  14. Object-constrained meshless deformable algorithm for high speed 3D nonrigid registration between CT and CBCT

    SciTech Connect

    Chen Ting; Kim, Sung; Goyal, Sharad; Jabbour, Salma; Zhou Jinghao; Rajagopal, Gunaretnum; Haffty, Bruce; Yue Ning

    2010-01-15

    Purpose: High-speed nonrigid registration between the planning CT and the treatment CBCT data is critical for real time image guided radiotherapy (IGRT) to improve the dose distribution and to reduce the toxicity to adjacent organs. The authors propose a new fully automatic 3D registration framework that integrates object-based global and seed constraints with the grayscale-based ''demons'' algorithm. Methods: Clinical objects were segmented on the planning CT images and were utilized as meshless deformable models during the nonrigid registration process. The meshless models reinforced a global constraint in addition to the grayscale difference between CT and CBCT in order to maintain the shape and the volume of geometrically complex 3D objects during the registration. To expedite the registration process, the framework was stratified into hierarchies, and the authors used a frequency domain formulation to diffuse the displacement between the reference and the target in each hierarchy. Also during the registration of pelvis images, they replaced the air region inside the rectum with estimated pixel values from the surrounding rectal wall and introduced an additional seed constraint to robustly track and match the seeds implanted into the prostate. The proposed registration framework and algorithm were evaluated on 15 real prostate cancer patients. For each patient, prostate gland, seminal vesicle, bladder, and rectum were first segmented by a radiation oncologist on planning CT images for radiotherapy planning purpose. The same radiation oncologist also manually delineated the tumor volumes and critical anatomical structures in the corresponding CBCT images acquired at treatment. These delineated structures on the CBCT were only used as the ground truth for the quantitative validation, while structures on the planning CT were used both as the input to the registration method and the ground truth in validation. By registering the planning CT to the CBCT, a

  15. Segmenting the papillary muscles and the trabeculae from high resolution cardiac CT through restoration of topological handles.

    PubMed

    Gao, Mingchen; Chen, Chao; Zhang, Shaoting; Qian, Zhen; Metaxas, Dimitris; Axel, Leon

    2013-01-01

    We introduce a novel algorithm for segmenting the high resolution CT images of the left ventricle (LV), particularly the papillary muscles and the trabeculae. High quality segmentations of these structures are necessary in order to better understand the anatomical function and geometrical properties of LV. These fine structures, however, are extremely challenging to capture due to their delicate and complex nature in both geometry and topology. Our algorithm computes the potential missing topological structures of a given initial segmentation. Using techniques from computational topology, e.g. persistent homology, our algorithm find topological handles which are likely to be the true signal. To further increase accuracy, these proposals are measured by the saliency and confidence from a trained classifier. Handles with high scores are restored in the final segmentation, leading to high quality segmentation results of the complex structures. PMID:24683968

  16. SPECT/CT Imaging of High-Risk Atherosclerotic Plaques using Integrin-Binding RGD Dimer Peptides

    PubMed Central

    Sun Yoo, Jung; Lee, Jonghwan; Ho Jung, Jae; Seok Moon, Byung; Kim, Soonhag; Chul Lee, Byung; Eun Kim, Sang

    2015-01-01

    Vulnerable atherosclerotic plaques with unique biological signatures are responsible for most major cardiovascular events including acute myocardial infarction and stroke. However, current clinical diagnostic approaches for atherosclerosis focus on anatomical measurements such as the degree of luminal stenosis and wall thickness. An abundance of neovessels with elevated expression of integrin αvβ3 is closely associated with an increased risk of plaque rupture. Herein we evaluated the potential of an αvβ3 integrin-targeting radiotracer, 99mTc-IDA-D-[c(RGDfK)]2, for SPECT/CT imaging of high-risk plaque in murine atherosclerosis models. In vivo uptake of 99mTc-IDA-D-[c(RGDfK)]2 was significantly higher in atherosclerotic aortas than in relatively normal aortas. Comparison with the negative-control peptide, 99mTc-IDA-D-[c(RADfK)]2, proved specific binding of 99mTc-IDA-D-[c(RGDfK)]2 for plaque lesions in in vivo SPECT/CT and ex vivo autoradiographic imaging. Histopathological characterization revealed that a prominent SPECT signal of 99mTc-IDA-D-[c(RGDfK)]2 corresponded to the presence of high-risk plaques with a large necrotic core, a thin fibrous cap, and vibrant neoangiogenic events. Notably, the RGD dimer based 99mTc-IDA-D-[c(RGDfK)]2 showed better imaging performance in comparison with the common monomeric RGD peptide probe 123I-c(RGDyV) and fluorescence tissue assay corroborated this. Our preclinical data demonstrated that 99mTc-IDA-D-[c(RGDfK)]2 SPECT/CT is a sensitive tool to noninvasively gauge atherosclerosis beyond vascular anatomy by assessing culprit plaque neovascularization. PMID:26123253

  17. CT based three dimensional dose-volume evaluations for high-dose rate intracavitary brachytherapy for cervical cancer

    PubMed Central

    2014-01-01

    Background In this study, high risk clinical target volumes (HR-CTVs) according to GEC-ESTRO guideline were contoured retrospectively based on CT images taken at the time of high-dose rate intracavitary brachytherapy (HDR-ICBT) and correlation between clinical outcome and dose of HR-CTV were analyzed. Methods Our study population consists of 51 patients with cervical cancer (Stages IB-IVA) treated with 50 Gy external beam radiotherapy (EBRT) using central shield combined with 2–5 times of 6 Gy HDR-ICBT with or without weekly cisplatin. Dose calculation was based on Manchester system and prescribed dose of 6 Gy were delivered for point A. CT images taken at the time of each HDR-ICBT were reviewed and HR-CTVs were contoured. Doses were converted to the equivalent dose in 2 Gy (EQD2) by applying the linear quadratic model (α/β = 10 Gy). Results Three-year overall survival, Progression-free survival, and local control rate was 82.4%, 85.3% and 91.7%, respectively. Median cumulative dose of HR-CTV D90 was 65.0 Gy (52.7-101.7 Gy). Median length from tandem to the most lateral edge of HR-CTV at the first ICBT was 29.2 mm (range, 18.0-51.9 mm). On univariate analysis, both LCR and PFS was significantly favorable in those patients D90 for HR-CTV was 60 Gy or greater (p = 0.001 and 0.03, respectively). PFS was significantly favorable in those patients maximum length from tandem to edge of HR-CTV at first ICBT was shorter than 3.5 cm (p = 0.042). Conclusion Volume-dose showed a relationship to the clinical outcome in CT based brachytherapy for cervical carcinoma. PMID:24938757

  18. The 2-micron plasmid as a nonselectable, stable, high copy number yeast vector

    NASA Technical Reports Server (NTRS)

    Ludwig, D. L.; Bruschi, C. V.

    1991-01-01

    The endogenous 2-microns plasmid of Saccharomyces cerevisiae has been used extensively for the construction of yeast cloning and expression plasmids because it is a native yeast plasmid that is able to be maintained stably in cells at high copy number. Almost invariably, these plasmid constructs, containing some or all 2-microns sequences, exhibit copy number levels lower than 2-microns and are maintained stably only under selective conditions. We were interested in determining if there was a means by which 2-microns could be utilized for vector construction, without forfeiting either copy number or nonselective stability. We identified sites in the 2-microns plasmid that could be used for the insertion of genetic sequences without disrupting 2-microns coding elements and then assessed subsequent plasmid constructs for stability and copy number in vivo. We demonstrate the utility of a previously described 2-microns recombination chimera, pBH-2L, for the manipulation and transformation of 2-microns as a pure yeast plasmid vector. We show that the HpaI site near the STB element in the 2-microns plasmid can be utilized to clone yeast DNA of at least 3.9 kb with no loss of plasmid stability. Additionally, the copy number of these constructs is as high as levels reported for the endogenous 2-microns.

  19. Large scale dynamics in a turbulent compressible rotor/stator cavity flow at high Reynolds number

    NASA Astrophysics Data System (ADS)

    Lachize, C.; Verhille, G.; Le Gal, P.

    2016-08-01

    This paper reports an experimental investigation of a turbulent flow confined within a rotor/stator cavity of aspect ratio close to unity at high Reynolds number. The experiments have been driven by changing both the rotation rate of the disk and the thermodynamical properties of the working fluid. This fluid is sulfur hexafluoride (SF6) whose physical properties are adjusted by imposing the operating temperature and the absolute pressure in a pressurized vessel, especially near the critical point of SF6 reached for T c = 45.58 ◦C, P c = 37.55 bar. This original set-up allows to obtain Reynolds numbers as high as 2 × 107 together with compressibility effects as the Mach number can reach 0.5. Pressure measurements reveal that the resulting fully turbulent flow shows both a direct and an inverse cascade as observed in rotating turbulence and in accordance with Kraichnan conjecture for 2D-turbulence. The spectra are however dominated by low-frequency peaks, which are subharmonics of the rotating disk frequency, involving large scale structures at small azimuthal wavenumbers. These modes appear for a Reynolds number around 105 and experience a transition at a critical Reynolds number Re c ≈ 106. Moreover they show an unexpected nonlinear behavior that we understand with the help of a low dimensional amplitude equations.

  20. Design and installation of a high Reynolds number recirculating water tunnel

    NASA Astrophysics Data System (ADS)

    Daniel, Libin

    The High-Reynolds Number Fluid Mechanics Laboratory has recently been established at Oklahoma State University (OSU). The three primary components of the laboratory are 1) a recirculating water tunnel, 2) a multiphase pipe flow facility, and 3) a multi-scale flow visualization system. This thesis focuses on the design and fabrication of the water tunnel, which will be used for high-Reynolds number turbulent boundary layer research. Two main design criteria for the water tunnel were to achieve a momentum thickness based Reynolds number in excess of 104 and to have high optical access to the flow surfaces in the test section. This is being achieved with a 1 m. long test section and a maximum flow speed of 10 m/s. This Reynolds number was targeted to bridge the gap between typical university water tunnels (103) and the world's largest water tunnel facilities (105). The water tunnel is powered by a 150 hp motor and a 4500 gpm capacity centrifugal pump. The water tunnel is designed for a maximum operating pressure of 40 psi. This will make the facility a low cost option to perform high-Reynolds number aerodynamic and hydrodynamic tests. Improved flow imaging capability is a major advantage to liquid based fluid facilities because of the increased density for seeding and reduced field-of-view for equivalent Reynolds number. The laboratory's state-of-the-art flow visualization system can be used for time-resolved and phase averaged stereo- particle-image-velocimetry (sPIV), laser-induced-fluorescence, and high-speed imaging. Design provisions are also made to allow a multi-phase loop to share the pump and motor configuration of this water tunnel facility. The major design decisions that went into the design of the water tunnel facility are discussed. The design considerations that were taken into account for the test section, flow conditioning sections and the entire flow loop are discussed in greater detail. The final configuration and the technical drawings of the water

  1. Instability of magnetized and differentially rotating stellar radiation zones with high magnetic Mach number

    NASA Astrophysics Data System (ADS)

    Rüdiger, G.; Schultz, M.; Kitchatinov, L. L.

    2016-03-01

    With applications to inner solar-type radiative zones, a linear theory is used to analyse the instability of a toroidal background field of dipolar parity, in the presence of density stratification, differential rotation and realistically small Prandtl numbers. The physical parameters are the Alfvén frequency ΩA, the global rotation rate Ω and the buoyancy frequency N with ΩA < Ω < N. Only the solutions for the wavelengths with the maximal growth rates are considered. If these scales are combined to estimate radial velocities, one finds that it hardly depends on the latitudinal shear and the magnetic Mach number. In the formulation of Schatzman the radial mixing of chemicals can be estimated as Re* = O(100) which indeed is necessary to dissipate the lithium in the solar tachocline with a time-scale of 1 Gyr. The calculated growth rates indicate a destabilization of the system for growing latitudinal shear except for small Mach numbers and antisolar shear. The ratio ε of the magnetic and the kinetic energy of the instability pattern only slightly depends on the shear but a strong dependence on the magnetic Mach number exists with ε ∝ Mm2. The effective magnetic Prandtl number reaches values O(103) so that for the stars with high magnetic Mach number the differential rotation decays much faster than the toroidal background field.

  2. Analysis of gas turbine engines using water and oxygen injection to achieve high Mach numbers and high thrust

    NASA Technical Reports Server (NTRS)

    Henneberry, Hugh M.; Snyder, Christopher A.

    1993-01-01

    An analysis of gas turbine engines using water and oxygen injection to enhance performance by increasing Mach number capability and by increasing thrust is described. The liquids are injected, either separately or together, into the subsonic diffuser ahead of the engine compressor. A turbojet engine and a mixed-flow turbofan engine (MFTF) are examined, and in pursuit of maximum thrust, both engines are fitted with afterburners. The results indicate that water injection alone can extend the performance envelope of both engine types by one and one-half Mach numbers at which point water-air ratios reach 17 or 18 percent and liquid specific impulse is reduced to some 390 to 470 seconds, a level about equal to the impulse of a high energy rocket engine. The envelope can be further extended, but only with increasing sacrifices in liquid specific impulse. Oxygen-airflow ratios as high as 15 percent were investigated for increasing thrust. Using 15 percent oxygen in combination with water injection at high supersonic Mach numbers resulted in thrust augmentation as high as 76 percent without any significant decrease in liquid specific impulse. The stoichiometric afterburner exit temperature increased with increasing oxygen flow, reaching 4822 deg R in the turbojet engine at a Mach number of 3.5. At the transonic Mach number of 0.95 where no water injection is needed, an oxygen-air ratio of 15 percent increased thrust by some 55 percent in both engines, along with a decrease in liquid specific impulse of 62 percent. Afterburner temperature was approximately 4700 deg R at this high thrust condition. Water and/or oxygen injection are simple and straightforward strategies to improve engine performance and they will add little to engine weight. However, if large Mach number and thrust increases are required, liquid flows become significant, so that operation at these conditions will necessarily be of short duration.

  3. Design and Predictions for High-Altitude (Low Reynolds Number) Aerodynamic Flight Experiment

    NASA Technical Reports Server (NTRS)

    Greer, Donald; Harmory, Phil; Krake, Keith; Drela, Mark

    2000-01-01

    A sailplane being developed at NASA Dryden Flight Research Center will support a high-altitude flight experiment. The experiment will measure the performance parameters or an airfoil at high altitudes (70,000 - 100,000 ft), low Reynolds numbers (2 x 10(exp 5) - 7 x 10(exp 5)), and high subsonic Mach numbers (0.5 and 0.65). The airfoil section lift and drag are determined from pilot and static pressure measurements. The locations of the separation bubble, Tollmien-Schlichting boundary-layer instability frequencies, and vortex shedding are measured from a hot-film strip. The details of the planned flight experiment are presented as well as several predictions of the airfoil performance.

  4. Design and Predictions for a High-Altitude (Low-Reynolds-Number) Aerodynamic Flight Experiment

    NASA Technical Reports Server (NTRS)

    Greer, Donald; Hamory, Phil; Krake, Keith; Drela, Mark

    1999-01-01

    A sailplane being developed at NASA Dryden Flight Research Center will support a high-altitude flight experiment. The experiment will measure the performance parameters of an airfoil at high altitudes (70,000 to 100,000 ft), low Reynolds numbers (200,000 to 700,000), and high subsonic Mach numbers (0.5 and 0.65). The airfoil section lift and drag are determined from pitot and static pressure measurements. The locations of the separation bubble, Tollmien-Schlichting boundary layer instability frequencies, and vortex shedding are measured from a hot-film strip. The details of the planned flight experiment are presented. Several predictions of the airfoil performance are also presented. Mark Drela from the Massachusetts Institute of Technology designed the APEX-16 airfoil, using the MSES code. Two-dimensional Navier-Stokes analyses were performed by Mahidhar Tatineni and Xiaolin Zhong from the University of California, Los Angeles, and by the authors at NASA Dryden.

  5. Porcine oocyte mtDNA copy number is high or low depending on the donor.

    PubMed

    Pedersen, Hanne Skovsgaard; Løvendahl, Peter; Larsen, Knud; Madsen, Lone Bruhn; Callesen, Henrik

    2016-08-01

    Oocyte capacity is relevant in understanding decreasing female fertility and in the use of assisted reproductive technologies in human and farm animals. Mitochondria are important to the development of a functionally good oocyte and the oocyte mtDNA copy number has been introduced as a useful parameter for prediction of oocyte competence. The aim of this study was to investigate: (i) if the oocyte donor has an influence on its oocyte's mtDNA copy number; and (ii) the relation between oocyte size and mtDNA copy number using pre- and postpubertal pig oocytes. Cumulus-oocyte complexes were collected from individual donor pigs. The oocytes were allocated into different size-groups, snap-frozen and single-oocyte mtDNA copy number was estimated by quantitative real-time PCR using the genes ND1 and COX1. Results showed that mean mtDNA copy number in oocytes from any individual donor could be categorized as either 'high' (≥100,000) or 'low' (<100,000) with no difference in threshold between pre- and postpubertal oocytes. No linear correlation was detected between oocyte size and mtDNA copy number within pre- and postpubertal oocytes. This study demonstrates the importance of the oocyte donor in relation to oocyte mtDNA copy number, irrespectively of the donor's puberty status and the oocyte's growth stage. Observations from this study facilitate both further investigations of the importance of mtDNA copy number and the unravelling of relations between different mitochondrial parameters and oocyte competence. PMID:26679989

  6. An experimental study of high Reynolds number turbulence in the atmosphere

    NASA Astrophysics Data System (ADS)

    Dhruva, Brindesh R.

    2000-11-01

    High Reynolds number turbulence in the atmospheric boundary layer has been investigated using constant temperature hot-wire anemometry. The Taylor microscale Reynolds numbers (Rλ) were typically between 5 × 103 at 2 meters in the salt flats of Western Utah and 2 × 104 at 35 meters on the meterological tower of Brookhaven National Laboratory in Long Island. The measurements were used to study the statistical properties of inertial range quantities, Reynolds stress and wind direction. The identification of possible self- similar behavior in the inertial range is a primary goal in turbulence research. To motivate the need for high Reynolds number measurements we demonstrate the Reynolds number effect on the existence and extent of the inertial range. We find that the inertial range is non-existent at typical laboratory Reynolds numbers. We thus turn to high Reynolds numbers and analyze the asymmetry in the probability distribution function (pdf) of the longitudinal velocity increment. We compute the scaling exponents of the positive and negative structure functions and find that the negative exponents are more anomalous than the positive ones. Furthermore, we quantify the contribution to the asymmetry-or the skewness-from different regions of the pdf. We find that the core region of the pdf is more or less symmetric and the skewness comes primarily from the rare large amplitude events contained in the tails of the pdf. We discuss this result in the context of the down-scale cascade of energy. Next it is shown that even at Rλ ~ 20,000 the structure functions do not scale unambiguously-although the situation is far better than that at low Reynolds numbers. By applying various filtering techniques and conditional sampling it is shown that this lack of strict scaling even at very high Reynolds numbers is due to large scale ``corrupting effects'' on the inertial range. We propose a plausible scheme to remove the large scale effects. Next, we characterize the

  7. Magnus effects at high angles of attack and critical Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Seginer, A.; Ringel, M.

    1983-01-01

    The Magnus force and moment experienced by a yawed, spinning cylinder were studied experimentally in low speed and subsonic flows at high angles of attack and critical Reynolds numbers. Flow-field visualization aided in describing a flow model that divides the Magnus phenomenon into a subcritical region, where reverse Magnus loads are experienced, and a supercritical region where these loads are not encountered. The roles of the spin rate, angle of attack, and crossflow Reynolds number in determining the boundaries of the subcritical region and the variations of the Magnus loads were studied.

  8. An experimental documentation of trailing-edge flows at high Reynolds number

    NASA Technical Reports Server (NTRS)

    Viswanath, P. R.; Cleary, J. W.; Seegmiller, H. L.

    1983-01-01

    Experiments documenting attached trailing-edge and near-wake flows at high Reynolds numbers are described. A long, airfoil-like model was tested at subsonic and low transonic Mach numbers, and both symmetrical and asymmetrical flows with pressure gradients upstream of the trailing edge were investigated. Model surface pressures and detailed mean and turbulence flow qualities were measured in the vicinity of the trailing edge and in the near-wake. The data obtained are of sufficient quality and detail to be useful as test cases in assessing turbulence models and calculation methods.

  9. The small-scale dynamo: breaking universality at high Mach numbers

    NASA Astrophysics Data System (ADS)

    Schleicher, Dominik R. G.; Schober, Jennifer; Federrath, Christoph; Bovino, Stefano; Schmidt, Wolfram

    2013-02-01

    The small-scale dynamo plays a substantial role in magnetizing the Universe under a large range of conditions, including subsonic turbulence at low Mach numbers, highly supersonic turbulence at high Mach numbers and a large range of magnetic Prandtl numbers Pm, i.e. the ratio of kinetic viscosity to magnetic resistivity. Low Mach numbers may, in particular, lead to the well-known, incompressible Kolmogorov turbulence, while for high Mach numbers, we are in the highly compressible regime, thus close to Burgers turbulence. In this paper, we explore whether in this large range of conditions, universal behavior can be expected. Our starting point is previous investigations in the kinematic regime. Here, analytic studies based on the Kazantsev model have shown that the behavior of the dynamo depends significantly on Pm and the type of turbulence, and numerical simulations indicate a strong dependence of the growth rate on the Mach number of the flow. Once the magnetic field saturates on the current amplification scale, backreactions occur and the growth is shifted to the next-larger scale. We employ a Fokker-Planck model to calculate the magnetic field amplification during the nonlinear regime, and find a resulting power-law growth that depends on the type of turbulence invoked. For Kolmogorov turbulence, we confirm previous results suggesting a linear growth of magnetic energy. For more general turbulent spectra, where the turbulent velocity scales with the characteristic length scale as uℓ∝ℓϑ, we find that the magnetic energy grows as (t/Ted)2ϑ/(1-ϑ), with t being the time coordinate and Ted the eddy-turnover time on the forcing scale of turbulence. For Burgers turbulence, ϑ = 1/2, quadratic rather than linear growth may thus be expected, as the spectral energy increases from smaller to larger scales more rapidly. The quadratic growth is due to the initially smaller growth rates obtained for Burgers turbulence. Similarly, we show that the characteristic

  10. Numerical simulations of high Knudsen number gas flows and microchannel electrokinetic liquid flows

    NASA Astrophysics Data System (ADS)

    Yan, Fang

    Low pressure and microchannel gas flows are characterized by high Knudsen numbers. Liquid flows in microchannels are characterized by non-conventional driving potentials like electrokinetic forces. The main thrust of the dissertation is to investigate these two different kinds of flows in gases and liquids respectively. High Knudsen number (Kn) gas flows were characterized by 'rarified' or 'microscale' behavior. Because of significant non-continuum effect, traditional CFD techniques are often inaccurate for analyzing high Kn number gas flows. The direct simulation Monte Carlo (DSMC) method offers an alternative to traditional CFD which retains its validity in slip and transition flow regimes. To validate the DSMC code, comparisons of simulation results with theoretical analysis and experimental data are made. The DSMC method was first applied to compute low pressure, high Kn flow fields in partially heated two dimensional channels. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nusselt number, Nu) were examined. The DSMC method was employed to explore mixing gas flows in two dimensional microchannels. Mixing of two gas streams (H2 and O2) was considered within a microchannel. The effect of the inlet-outlet pressure difference, the pressure ratio of the incoming streams and the accommodation coefficient of the solid wall on mixing length were all examined. Parallelization of a three-dimensional DSMC code was implemented using OpenMP procedure on a shared memory multi-processor computer. The parallel code was used to simulate 3D high Kn number Couette flow and the flow characteristics are found to be very different from their continuum counterparts. A mathematical model describing electrokinetically driven mass transport phenomena in microfabricated chip devices will also be presented. The model accounts for the principal physical phenomena affecting

  11. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results.

    PubMed

    Manhart, Michael T; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K; Hornegger, Joachim; Doerfler, Arnd

    2014-08-21

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved. PMID:25069101

  12. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results

    NASA Astrophysics Data System (ADS)

    Manhart, Michael T.; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K.; Hornegger, Joachim; Doerfler, Arnd

    2014-08-01

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved.

  13. Measurements of the wall-normal velocity component in very high Reynolds number pipe flow

    NASA Astrophysics Data System (ADS)

    Vallikivi, Margit; Hultmark, Marcus; Smits, Alexander J.

    2012-11-01

    Nano-Scale Thermal Anemometry Probes (NSTAPs) have recently been developed and used to study the scaling of the streamwise component of turbulence in pipe flow over a very large range of Reynolds numbers. This probe has an order of magnitude higher spatial and temporal resolution than regular hot wires, allowing it to resolve small scale motions at very high Reynolds numbers. Here use a single inclined NSTAP probe to study the scaling of the wall normal component of velocity fluctuations in the same flow. These new probes are calibrated using a method that is based on the use of the linear stress region of a fully developed pipe flow. Results on the behavior of the wall-normal component of velocity for Reynolds numbers up to 2 million are reported. Supported under NR Grant N00014-09-1-0263 (program manager Ron Joslin) and NSF Grant CBET-1064257 (program manager Henning Winter).

  14. Operating characteristics of the Langley Mach 10 high Reynolds number helium tunnel

    NASA Technical Reports Server (NTRS)

    Watson, R. D.; Morris, D. J.; Fischer, M. C.

    1974-01-01

    Operating characteristics of the Langley Mach 10 high Reynolds number helium tunnel are presented for stagnation pressures from 138 N/sq cm to 1655 N/sq cm. The characteristics include detailed Mach number surveys in the test section from which usable core size and regions of disturbed flow were determined, preliminary blockage test results, and maximum run time to be expected at various stagnation pressures. Important tunnel dimensions including details of the model mounting apparatus are given. Measurements show the variation in average core Mach number in the test section to be between 9.4 and 10 for the present range of test conditions. The core radius is from 23 cm to 31.5 cm, depending on stagnation pressure and axial location in the test section.

  15. Noise-free high-efficiency photon-number-resolving detectors

    SciTech Connect

    Rosenberg, Danna; Lita, Adriana E.; Miller, Aaron J.; Nam, Sae Woo

    2005-06-15

    High-efficiency optical detectors that can determine the number of photons in a pulse of monochromatic light have applications in a variety of physics studies, including post-selection-based entanglement protocols for linear optics quantum computing and experiments that simultaneously close the detection and communication loopholes of Bell's inequalities. Here we report on our demonstration of fiber-coupled, noise-free, photon-number-resolving transition-edge sensors with 88% efficiency at 1550 nm. The efficiency of these sensors could be made even higher at any wavelength in the visible and near-infrared spectrum without resulting in a higher dark-count rate or degraded photon-number resolution.

  16. Frontline Science: Splenic progenitors aid in maintaining high neutrophil numbers at sites of sterile chronic inflammation.

    PubMed

    Jhunjhunwala, Siddharth; Alvarez, David; Aresta-DaSilva, Stephanie; Tang, Katherine; Tang, Benjamin C; Greiner, Dale L; Newburger, Peter E; von Andrian, Ulrich H; Langer, Robert; Anderson, Daniel G

    2016-08-01

    Neutrophils are constantly generated from hematopoietic stem and progenitor cells in the bone marrow to maintain high numbers in circulation. A considerable number of neutrophils and their progenitors have been shown to be present in the spleen too; however, their exact role in this organ remains unclear. Herein, we sought to study the function of splenic neutrophils and their progenitors using a mouse model for sterile, peritoneal inflammation. In this microcapsule device implantation model, we show chronic neutrophil presence at implant sites, with recruitment from circulation as the primary mechanism for their prevalence in the peritoneal exudate. Furthermore, we demonstrate that progenitor populations in the spleen play a key role in maintaining elevated neutrophil numbers. Our results provide new insight into the role for splenic neutrophils and their progenitors and establish a model to study neutrophil function during sterile inflammation. PMID:26965635

  17. Optimal image reconstruction phase at low and high heart rates in dual-source CT coronary angiography.

    PubMed

    Araoz, Philip A; Kirsch, Jacobo; Primak, Andrew N; Braun, Natalie N; Saba, Osama; Williamson, Eric E; Harmsen, W Scott; Mandrekar, Jayawant N; McCollough, Cynthia H

    2009-12-01

    The purpose of this study was to determine the cardiac phase having the highest coronary sharpness for low and high heart rate patients scanned with dual source CT (DSCT) and to compare coronary image sharpness over different cardiac phases. DSCT coronary CT scans for 30 low heart rate (< or =70 beats per minute- bpm) and 30 high heart rate (>70 bpm) patients were reconstructed into different cardiac phases, starting at 30% and increasing at 5% increments until 70%. A blinded observer graded image sharpness per coronary segment, from which sharpness scores were produced for the right (RCA), left main (LM), left anterior descending (LAD), and circumflex (Cx) coronary arteries. For each coronary artery, the phase with maximal image sharpness was identified with repeated measures analysis of variance. Comparison of coronary sharpness between low and high heart rate patients was made using generalized estimating equations. For low heart rates the highest sharpness scores for all four vessels (RCA, LM, LAD, and Cx) were at the 65 or 70% phase, which are end-diastolic cardiac phases. For high heart rates the highest sharpness scores were between the 35 and 45% phases, which are end-systolic phases. Low heart rate patients had higher coronary sharpness at most cardiac phases; however, patients with high heart rates had higher coronary sharpness in the 45% phase for all four vessels (P < 0.0001). Using DSCT scanning, optimal image sharpness is obtained in end-diastole at low heart rates and in end-systole in high heart rates. PMID:19669664

  18. Optimal image reconstruction phase at low and high heart rates in dual-source CT coronary angiography

    PubMed Central

    Kirsch, Jacobo; Primak, Andrew N.; Braun, Natalie N.; Saba, Osama; Williamson, Eric E.; Harmsen, W. Scott; Mandrekar, Jayawant N.; McCollough, Cynthia H.

    2009-01-01

    The purpose of this study was to determine the cardiac phase having the highest coronary sharpness for low and high heart rate patients scanned with dual source CT (DSCT) and to compare coronary image sharpness over different cardiac phases. DSCT coronary CT scans for 30 low heart rate (≤ 70 beats per minute- bpm) and 30 high heart rate (>70 bpm) patients were reconstructed into different cardiac phases, starting at 30% and increasing at 5% increments until 70%. A blinded observer graded image sharpness per coronary segment, from which sharpness scores were produced for the right (RCA), left main (LM), left anterior descending (LAD), and circumflex (Cx) coronary arteries. For each coronary artery, the phase with maximal image sharpness was identified with repeated measures analysis of variance. Comparison of coronary sharpness between low and high heart rate patients was made using generalized estimating equations. For low heart rates the highest sharpness scores for all four vessels (RCA, LM, LAD, and Cx) were at the 65 or 70% phase, which are end-diastolic cardiac phases. For high heart rates the highest sharpness scores were between the 35 and 45% phases, which are end-systolic phases. Low heart rate patients had higher coronary sharpness at most cardiac phases; however, patients with high heart rates had higher coronary sharpness in the 45% phase for all four vessels (P < 0.0001). Using DSCT scanning, optimal image sharpness is obtained in end-diastole at low heart rates and in end-systole in high heart rates. PMID:19669664

  19. Measurements of Molecular Mixing in a High Schmidt Number Rayleigh-Taylor Mixing Layer

    SciTech Connect

    Mueschke, N J; Schilling, O; Youngs, D L; Andrews, M

    2007-12-03

    Molecular mixing measurements are performed for a high Schmidt number (Sc {approx} 10{sup 3}), small Atwood number (A {approx} 7.5 x 10{sup -4}) buoyancy-driven turbulent Rayleigh-Taylor mixing layer in a water channel facility. Salt was added to the top stream to create the desired density difference. The degree of molecular mixing was measured as a function of time by monitoring a diffusion-limited chemical reaction between the two fluid streams. The pH of each stream was modified by the addition of acid or alkali such that a local neutralization reaction occurred as the two fluids molecularly mixed. The progress of this neutralization reaction was tracked by the addition of phenolphthalein - a pH-sensitive chemical indicator - to the acidic stream. Accurately calibrated backlit optical techniques were used to measure the average concentration of the colored chemical indicator. Comparisons of chemical product formation for pre-transitional buoyancy- and shear-driven mixing layers are given. It is also shown that experiments performed at different equivalence ratios (acid/alkali concentration) can be combined to obtain a mathematical relationship between the colored product formed and the density variance. This relationship was used to obtain high-fidelity, quantitative measures of the degree of molecular mixing which are independent of probe resolution constraints. The dependence of such mixing parameters on the Schmidt and Reynolds numbers is examined by comparing the current Sc {approx} 10{sup 3} measurements with Sc = 0.7 gas-phase and Pr = 7 liquid-phase measurements. This comparison indicates that the Schmidt number has a large effect on the bulk quantity of mixed fluid at small Reynolds numbers Re{sub h} < 10{sup 3}. At late times, all mixing parameters indicated a greater degree of molecular mixing and a decreased Schmidt number dependence. Implications for the development and quantitative assessment of turbulent transport and mixing models appropriate for

  20. A highly efficient bead extraction technique with low bead number for digital microfluidic immunoassay.

    PubMed

    Huang, Cheng-Yeh; Tsai, Po-Yen; Lee, I-Chin; Hsu, Hsin-Yun; Huang, Hong-Yuan; Fan, Shih-Kang; Yao, Da-Jeng; Liu, Cheng-Hsien; Hsu, Wensyang

    2016-01-01

    Here, we describe a technique to manipulate a low number of beads to achieve high washing efficiency with zero bead loss in the washing process of a digital microfluidic (DMF) immunoassay. Previously, two magnetic bead extraction methods were reported in the DMF platform: (1) single-side electrowetting method and (2) double-side electrowetting method. The first approach could provide high washing efficiency, but it required a large number of beads. The second approach could reduce the required number of beads, but it was inefficient where multiple washes were required. More importantly, bead loss during the washing process was unavoidable in both methods. Here, an improved double-side electrowetting method is proposed for bead extraction by utilizing a series of unequal electrodes. It is shown that, with proper electrode size ratio, only one wash step is required to achieve 98% washing rate without any bead loss at bead number less than 100 in a droplet. It allows using only about 25 magnetic beads in DMF immunoassay to increase the number of captured analytes on each bead effectively. In our human soluble tumor necrosis factor receptor I (sTNF-RI) model immunoassay, the experimental results show that, comparing to our previous results without using the proposed bead extraction technique, the immunoassay with low bead number significantly enhances the fluorescence signal to provide a better limit of detection (3.14 pg/ml) with smaller reagent volumes (200 nl) and shorter analysis time (<1 h). This improved bead extraction technique not only can be used in the DMF immunoassay but also has great potential to be used in any other bead-based DMF systems for different applications. PMID:26858807

  1. Two-dimensional temperature distribution measurement of flames by absorption CT employing CO{sub 2} (Experimental study on the wave number employed and the accuracy of measurement)

    SciTech Connect

    Wakai, Kazunori; Moroto, Masakazu; Takahashi, Shuhei; Bhattacharjee, S.

    1999-07-01

    The authors have developed the algorithm of infrared two-band absorption CT (computed tomography) not only for short optical path where Lambert-Beer law is applicable but also for long optical path where some band model should be applied. The authors have also shown employing CO{sub 2} as an absorption medium, statistical model as a band model and Curtis-Godson model to treat non-uniform temperature fields that when optical path is long and spectrum has steep change, there are suitable wavelengths and widths to keep good accuracy. However, it was done only by computer simulation, and in this report, those results are discussed experimentally. The flat burner was used to compare temperature measured by above method with the temperature measured by sodium D-line reversal method. The results showed good correspondence and it means that the predicted suitable wavelengths and widths are experimentally confirmed. The accuracy, namely, standard deviation of the temperature, at the best wavelength conditions was lower than 20K. Temperature distributions around non-uniform temperature distribution on the flat disk burner and domestic boiler were also measured as applications and the results show that this method is applicable for the measurement of rather complicated two-dimensional temperature distributions.

  2. NASA High-Reynolds Number Circulation Control Research - Overview of CFD and Planned Experiments

    NASA Technical Reports Server (NTRS)

    Milholen, W. E., II; Jones, Greg S.; Cagle, Christopher M.

    2010-01-01

    A new capability to test active flow control concepts and propulsion simulations at high Reynolds numbers in the National Transonic Facility at the NASA Langley Research Center is being developed. This technique is focused on the use of semi-span models due to their increased model size and relative ease of routing high-pressure air to the model. A new dual flow-path high-pressure air delivery station has been designed, along with a new high performance transonic sem -si pan wing model. The modular wind tunnel model is designed for testing circulation control concepts at both transonic cruise and low-speed high-lift conditions. The ability of the model to test other active flow control techniques will be highlighted. In addition, a new higher capacity semi-span force and moment wind tunnel balance has been completed and calibrated to enable testing at transonic conditions.

  3. High-performance C-arm cone-beam CT guidance of thoracic surgery

    NASA Astrophysics Data System (ADS)

    Schafer, Sebastian; Otake, Yoshito; Uneri, Ali; Mirota, Daniel J.; Nithiananthan, Sajendra; Stayman, J. W.; Zbijewski, Wojciech; Kleinszig, Gerhard; Graumann, Rainer; Sussman, Marc; Siewerdsen, Jeffrey H.

    2012-02-01

    Localizing sub-palpable nodules in minimally invasive video-assisted thoracic surgery (VATS) presents a significant challenge. To overcome inherent problems of preoperative nodule tagging using CT fluoroscopic guidance, an intraoperative C-arm cone-beam CT (CBCT) image-guidance system has been developed for direct localization of subpalpable tumors in the OR, including real-time tracking of surgical tools (including thoracoscope), and video-CBCT registration for augmentation of the thoracoscopic scene. Acquisition protocols for nodule visibility in the inflated and deflated lung were delineated in phantom and animal/cadaver studies. Motion compensated reconstruction was implemented to account for motion induced by the ventilated contralateral lung. Experience in CBCT-guided targeting of simulated lung nodules included phantoms, porcine models, and cadavers. Phantom studies defined low-dose acquisition protocols providing contrast-to-noise ratio sufficient for lung nodule visualization, confirmed in porcine specimens with simulated nodules (3-6mm diameter PE spheres, ~100-150HU contrast, 2.1mGy). Nodule visibility in CBCT of the collapsed lung, with reduced contrast according to air volume retention, was more challenging, but initial studies confirmed visibility using scan protocols at slightly increased dose (~4.6-11.1mGy). Motion compensated reconstruction employing a 4D deformation map in the backprojection process reduced artifacts associated with motion blur. Augmentation of thoracoscopic video with renderings of the target and critical structures (e.g., pulmonary artery) showed geometric accuracy consistent with camera calibration and the tracking system (2.4mm registration error). Initial results suggest a potentially valuable role for CBCT guidance in VATS, improving precision in minimally invasive, lungconserving surgeries, avoid critical structures, obviate the burdens of preoperative localization, and improve patient safety.

  4. How are Strouhal number, drag, and efficiency adjusted in high level underwater monofin-swimming?

    PubMed

    Nicolas, Guillaume; Bideau, Benoit; Colobert, Briac; Berton, Eric

    2007-06-01

    Strouhal number (St) corresponds to a wake parameter based on the tail kinematics of swimming animals according to St=A.f/U, where f is the stroke frequency, A is the fin-beat peak-to-peak amplitude, and U is the forward speed. St number is a trade-off between amplitude and frequency that generates a forward velocity. This parameter may therefore be affected by swimming technique, which can be evaluated through active drag (AD) and Froude efficiency (eta(F)). The aim of our study was therefore to (1) investigate the range of AD and eta(F) values for high level monofin-swimmers, (2) explore the range of St numbers, and (3) examine to what extent this latter non-dimensional parameter may affect AD and eta(F). To this end, experiments have been conducted on 12 international level monofin-swimmers. St number, eta(F) (calculated according to the elongated-body theory), and AD (computed with velocity perturbation method) were calculated at the same time for an underwater fin-swimming trial, at maximal speed. Lowest values of St numbers (St=0.34) corresponded to fin-swimmers with highest velocities (R=-.77, p<.05), highest efficiencies (R=-.86, p<.001), and lowest active drag (R=.91, p<.001). On the one hand, AD was increased with vertical motion of the fin (R=.84, p<.001), which increased cross-sectional area (R=.78, p<.05). On the other hand, efficiencies showed a tendency to peak at eta(F)=0.82 in a narrow range of St numbers close to 0.4. This St range corresponded to the upper limit of the 0.25-0.4 range usually claimed for maximum efficiency of marine and flying animals. Such results suggest that increasing efficiency and reducing drag improves performance per se (regardless how these parameters are related with St number). PMID:17509711

  5. On the instabilities of supersonic mixing layers - A high-Mach-number asymptotic theory

    NASA Technical Reports Server (NTRS)

    Balsa, Thomas F.; Goldstein, M. E.

    1990-01-01

    The stability of a family of tanh mixing layers is studied at large Mach numbers using perturbation methods. It is found that the eigenfunction develops a multilayered structure, and the eigenvalue is obtained by solving a simplified version of the Rayleigh equation (with homogeneous boundary conditions) in one of these layers which lies in either of the external streams. This analysis leads to a simple hypersonic similarity law which explains how spatial and temporal phase speeds and growth rates scale with Mach number and temperature ratio. Comparisons are made with numerical results, and it is found that this similarity law provides a good qualitative guide for the behavior of the instability at high Mach numbers. In addition to this asymptotic theory, some fully numerical results are also presented (with no limitation on the Mach number) in order to explain the origin of the hypersonic modes (through mode splitting) and to discuss the role of oblique modes over a very wide range of Mach number and temperature ratio.

  6. The response of hot wires in high Reynolds-number turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Li, J. D.; McKeon, B. J.; Jiang, W.; Morrison, J. F.; Smits, A. J.

    2004-05-01

    Issues concerning the accuracy of hot-wire measurements in turbulent pipe flow are addressed for pipe Reynolds numbers up to 6 × 106 and hot-wire Reynolds numbers up to Rew ap 250. These include the optimization of spatial and temporal resolution and the associated feature of signal-to-noise ratio. Very high wire Reynolds numbers enable the use of wires with reduced length-to-diameter ratios compared to those typical of atmospheric conditions owing to increased wire Nusselt numbers. Simulation of the steady-state heat balance for the wire and the unetched portion of wire are used to assess static end-conduction effects: they are used to calculate wire Biot numbers, \\sqrt{c_0}l , and fractional end-conduction losses, sgr, which confirm the 'conduction-only' theory described by Corrsin. They show that, at Rew ap 250, the wire length-to-diameter ratio can be reduced to about 50, while keeping \\sqrt{c_0}l\\gt3 and sgr < 7% in common with accepted limits at Rew ap 3. It is shown that these limits depend additionally on the choice of wire material and the length of unetched wire. The dynamic effects of end-cooling are also assessed using the conduction-only theory.

  7. Nonlocal interactions in hydrodynamic turbulence at high Reynolds numbers: the slow emergence of scaling laws.

    PubMed

    Mininni, P D; Alexakis, A; Pouquet, A

    2008-03-01

    We analyze the data stemming from a forced incompressible hydrodynamic simulation on a grid of 2048(3) regularly spaced points, with a Taylor Reynolds number of R(lambda) ~ 1300. The forcing is given by the Taylor-Green vortex, which shares similarities with the von Kàrmàn flow used in several laboratory experiments; the computation is run for ten turnover times in the turbulent steady state. At this Reynolds number the anisotropic large scale flow pattern, the inertial range, the bottleneck, and the dissipative range are clearly visible, thus providing a good test case for the study of turbulence as it appears in nature. Triadic interactions, the locality of energy fluxes, and longitudinal structure functions of the velocity increments are computed. A comparison with runs at lower Reynolds numbers is performed and shows the emergence of scaling laws for the relative amplitude of local and nonlocal interactions in spectral space. Furthermore, the scaling of the Kolmogorov constant, and of skewness and flatness of velocity increments is consistent with previous experimental results. The accumulation of energy in the small scales associated with the bottleneck seems to occur on a span of wave numbers that is independent of the Reynolds number, possibly ruling out an inertial range explanation for it. Finally, intermittency exponents seem to depart from standard models at high R(lambda), leaving the interpretation of intermittency an open problem. PMID:18517510

  8. Assessment of microcalcifications with limited number of high-precision macrobiopsies.

    PubMed

    Harries, Richard; Lawson, Sarah; Bruckers, Liesbeth

    2010-09-01

    Stereotactic biopsy assessment of microcalcification clusters with direct and frontal macrobiopsies was performed in a population of 46 women screened for breast cancer. The only clinical finding in these women was microcalcification. Sensitivity of the procedure was 98% and calcifications were detected in 107 out of 148 tissue specimens (73%). This is the highest reported ratio so far. Interestingly, the total number of cores was inversely correlated with the success rate, suggesting that the accuracy of the direct and frontal approach is high. Four out of 46 women underwent surgery for malignancy indicating that 41 women escaped intervention with a mean follow-up of at least 1 year. Patient satisfaction is high, in particular regarding reported pain, fear and overall appreciation. No complications were seen. The data suggest that a lower number of macrobiopsies for microcalcifications could be acceptable with direct and frontal biopsy methods without reducing sensitivity. Lowering the number of biopsies can optimize the interpretation of surgical margin and reduce the number of biopsy-related mastectomies. PMID:20495463

  9. The use of small fraction numbers in high dose-rate gynaecological afterloading: some radiobiological considerations.

    PubMed

    Dale, R G

    1990-04-01

    Using commonly assumed alpha/beta ratios for tumours and late-reacting tissues, the linear-quadratic (LQ) model has been used to compare low dose-rate (LDR) gynaecological treatment with high dose-rate (HDR) techniques given in small fraction numbers. Even in the absence of relatively favourable tissue recovery constants (mu values) it is shown that, provided a modest extra amount of geometrical sparing of critical tissues is available (by means of spacing or shielding), HDR treatment in a small number of fractions may be used in place of an LDR regime without loss of therapeutic ratio. This general result, although not universally true, does indicate that HDR treatment delivered in a small number of fractions may be more feasible than is sometimes thought. These findings do not contradict currently accepted radiobiological philosophy, which cautions against the use of small numbers of high-dose fractions. Primarily they serve to emphasize the importance of the recommendations of the ICRU (1985), which stress the need to consider the complete time-dose pattern of radiation delivery to all the critical tissues in an intracavitary treatment. PMID:2346867

  10. On the high Mach number shock structure singularity caused by overreach of Maxwellian molecules

    SciTech Connect

    Myong, R. S.

    2014-05-15

    The high Mach number shock structure singularity arising in moment equations of the Boltzmann equation was investigated. The source of the singularity is shown to be the unbalanced treatment between two high order kinematic and dissipation terms caused by the overreach of Maxwellian molecule assumption. In compressive gaseous flow, the high order stress-strain coupling term of quadratic nature will grow far faster than the strain term, resulting in an imbalance with the linear dissipation term and eventually a blow-up singularity in high thermal nonequilibrium. On the other hand, the singularity arising from unbalanced treatment does not occur in the case of velocity shear and expansion flows, since the high order effects are cancelled under the constraint of the free-molecular asymptotic behavior. As an alternative method to achieve the balanced treatment, Eu's generalized hydrodynamics, consistent with the second law of thermodynamics, was revisited. After introducing the canonical distribution function in exponential form and applying the cumulant expansion to the explicit calculation of the dissipation term, a natural platform suitable for the balanced treatment was derived. The resulting constitutive equation with the nonlinear factor was then shown to be well-posed for all regimes, effectively removing the high Mach number shock structure singularity.

  11. On the Design of Lifting Airfoils with High Critical Mach Number Using Full Potential Theory

    NASA Astrophysics Data System (ADS)

    Kropinski, M. C. A.

    We wish to construct airfoils that have the highest free-stream Mach number for a given set of geometric constraints for which the flow is nowhere supersonic. Nonlifting airfoils that maximize the critical Mach number for a given cross-sectional area are known to possess long sonic segments at their critical speed. To construct lifting airfoils, we proceed under the conjecture that an airfoil with a high value of has the longest possible arc length of sonic velocity over its upper and lower surface. In Kropinski etal. (1995) the lifting problem was tackled in transonic small-disturbance theory. In this paper we numerically construct lifting airfoils with high using the full potential theory and we show that these airfoils have significantly higher than some standard airfoils. We also construct airfoils with higher values of the lift coefficient, by relaxing the speed constraint on the lower surface of the airfoil to have a value less than sonic.

  12. A multilocus variable number tandem repeat analysis assay provides high discrimination for genotyping Leptospira santarosai strains

    PubMed Central

    Hamond, Camila; Pinna, Melissa; Medeiros, Marco Alberto; Bourhy, Pascale; Lilenbaum, Walter

    2015-01-01

    Considering the prevalence of Leptospira santarosai infections in the Americas and the scarce information about the species, we aimed to apply a multilocus variable number tandem repeat (VNTR) analysis (MLVA) for the molecular typing of L. santarosai isolates from various sources. Amplification of three VNTR loci selected from L. santarosai genome sequences resulted in a wide range of sizes for the amplified products amongst the 21 L. santarosai strains analysed. This suggested a variation in tandem repeat copy numbers in the VNTR loci. secY sequencing also showed a high nucleotide diversity, confirming the MLVA data. In conclusion, this novel MLVA provided a high level of discrimination between L. santarosai isolates, and this new typing tool could be used to investigate leptospirosis in regions where L. santarosai predominates. PMID:25721051

  13. A third-order-accurate upwind scheme for Navier-Stokes solutions at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Agarwal, R. K.

    1981-01-01

    A third-order-accurate upwind scheme is presented for solution of the steady two-dimensional Navier-Stokes equations in stream-function/vorticity form. The scheme is found to be accurate and stable at high Reynolds numbers. A series of test computations is performed on flows with large recirculating regions. In particular, highly accurate solutions are obtained for flow in a driven square cavity up to Reynolds numbers of 10,000. These computations are used to critically evaluate the accuracy of other existing first- and second-order-accurate upwind schemes. In addition, computations are carried out for flow in a channel with symmetric sudden expansion, flow in a channel with a symmetrically placed blunt base, and the flowfield of an impinging jet. Good agreement is obtained with the computations of other investigators as well as with the available experimental data.

  14. Detached eddy simulation of high-Reynolds-number turbulent flows using the immersed boundary method

    NASA Astrophysics Data System (ADS)

    Bernardini, Matteo; Pirozzoli, Sergio; Orlandi, Paolo

    2015-11-01

    Detached Eddy Simulation based on the Spalart-Allmaras turbulence model is applied in conjunction with the immersed boundary method to simulate high-Reynolds number turbulent flows in complex geometries. A fourth-order, finite-difference solver capable of discretely preserving the kinetic energy in the limit of inviscid flow is adopted to solve the compressible Navier-Stokes equations and model-consistent, adaptive wall functions are employed to provide the proper numerical boundary conditions at the fluid/solid interface. Numerical tests, performed for several configurations involving massively separated flows, demonstrate that computations at high-Reynolds number, as typically occurring in flows of industrial relevance, can be successfully carried out using the immersed boundary strategy, providing predictions whose accuracy is comparable to that of standard, body-fitted, structured or unstructured flow solvers.

  15. Technical Note: Skin thickness measurements using high-resolution flat-panel cone-beam dedicated breast CT

    SciTech Connect

    Shi Linxi; Vedantham, Srinivasan; Karellas, Andrew; O'Connell, Avice M.

    2013-03-15

    Purpose: To determine the mean and range of location-averaged breast skin thickness using high-resolution dedicated breast CT for use in Monte Carlo-based estimation of normalized glandular dose coefficients. Methods: This study retrospectively analyzed image data from a clinical study investigating dedicated breast CT. An algorithm similar to that described by Huang et al.['The effect of skin thickness determined using breast CT on mammographic dosimetry,' Med. Phys. 35(4), 1199-1206 (2008)] was used to determine the skin thickness in 137 dedicated breast CT volumes from 136 women. The location-averaged mean breast skin thickness for each breast was estimated and the study population mean and range were determined. Pathology results were available for 132 women, and were used to investigate if the distribution of location-averaged mean breast skin thickness varied with pathology. The effect of surface fitting to account for breast curvature was also studied. Results: The study mean ({+-} interbreast SD) for breast skin thickness was 1.44 {+-} 0.25 mm (range: 0.87-2.34 mm), which was in excellent agreement with Huang et al. Based on pathology, pair-wise statistical analysis (Mann-Whitney test) indicated that at the 0.05 significance level, there were no significant difference in the location-averaged mean breast skin thickness distributions between the groups: benign vs malignant (p= 0.223), benign vs hyperplasia (p= 0.651), hyperplasia vs malignant (p= 0.229), and malignant vs nonmalignant (p= 0.172). Conclusions: Considering this study used a different clinical prototype system, and the study participants were from a different geographical location, the observed agreement between the two studies suggests that the choice of 1.45 mm thick skin layer comprising the epidermis and the dermis for breast dosimetry is appropriate. While some benign and malignant conditions could cause skin thickening, in this study cohort the location-averaged mean breast skin thickness

  16. PUFKEY: a high-security and high-throughput hardware true random number generator for sensor networks.

    PubMed

    Li, Dongfang; Lu, Zhaojun; Zou, Xuecheng; Liu, Zhenglin

    2015-01-01

    Random number generators (RNG) play an important role in many sensor network systems and applications, such as those requiring secure and robust communications. In this paper, we develop a high-security and high-throughput hardware true random number generator, called PUFKEY, which consists of two kinds of physical unclonable function (PUF) elements. Combined with a conditioning algorithm, true random seeds are extracted from the noise on the start-up pattern of SRAM memories. These true random seeds contain full entropy. Then, the true random seeds are used as the input for a non-deterministic hardware RNG to generate a stream of true random bits with a throughput as high as 803 Mbps. The experimental results show that the bitstream generated by the proposed PUFKEY can pass all standard national institute of standards and technology (NIST) randomness tests and is resilient to a wide range of security attacks. PMID:26501283

  17. PUFKEY: A High-Security and High-Throughput Hardware True Random Number Generator for Sensor Networks

    PubMed Central

    Li, Dongfang; Lu, Zhaojun; Zou, Xuecheng; Liu, Zhenglin

    2015-01-01

    Random number generators (RNG) play an important role in many sensor network systems and applications, such as those requiring secure and robust communications. In this paper, we develop a high-security and high-throughput hardware true random number generator, called PUFKEY, which consists of two kinds of physical unclonable function (PUF) elements. Combined with a conditioning algorithm, true random seeds are extracted from the noise on the start-up pattern of SRAM memories. These true random seeds contain full entropy. Then, the true random seeds are used as the input for a non-deterministic hardware RNG to generate a stream of true random bits with a throughput as high as 803 Mbps. The experimental results show that the bitstream generated by the proposed PUFKEY can pass all standard national institute of standards and technology (NIST) randomness tests and is resilient to a wide range of security attacks. PMID:26501283

  18. Electron heating in a Monte Carlo model of a high Mach number, supercritical, collisionless shock

    NASA Technical Reports Server (NTRS)

    Ellison, Donald C.; Jones, Frank C.

    1987-01-01

    Preliminary work in the investigation of electron injection and acceleration at parallel shocks is presented. A simple model of electron heating that is derived from a unified shock model which includes the effects of an electrostatic potential jump is described. The unified shock model provides a kinetic description of the injection and acceleration of ions and a fluid description of electron heating at high Mach number, supercritical, and parallel shocks.

  19. Simulation of transient flow in a shock tunnel and a high Mach number nozzle

    NASA Technical Reports Server (NTRS)

    Jacobs, P. A.

    1991-01-01

    A finite volume Navier-Stokes code was used to simulate the shock reflection and nozzle starting processes in an axisymmetric shock tube and a high Mach number nozzle. The simulated nozzle starting processes were found to match the classical quasi-1-D theory and some features of the experimental measurements. The shock reflection simulation illustrated a new mechanism for the driver gas contamination of the stagnated test gas.

  20. Heat transfer for falling film evaporation of industrially relevant fluids up to very high Prandtl numbers

    NASA Astrophysics Data System (ADS)

    Gourdon, Mathias; Karlsson, Erik; Innings, Fredrik; Jongsma, Alfred; Vamling, Lennart

    2016-02-01

    In many industrial applications, falling film evaporation is an attractive technique for solvent removal due to high heat transfer and low residence times. Examples are the powder production in the dairy industry and in kraft pulp production process to remove water from so called black liquor. Common for both applications is that the fluids exhibit high viscosities in industrial practice. In this paper, results from experimental studies on both black liquor and a dairy product are reported for Prandtl numbers up to 800. The results are compared with several existing correlation in literature, and the need for a modified correlation is recognized especially to cover higher Prandtl-numbers. The following correlation for the turbulent flow region with 3 < Pr < 800 was derived from the data: {Nu}t = 0.0085 \\cdot Re^{0.2} \\cdot {Pr^{0.65}} The correlation has been compared to literature data from one additional study on two other fluids (propylene glycol and cyclohexanol) with fairly high Prandtl-numbers, from 40 to 58 and from 45 to 155 respectively and the agreement was within ±40 %.

  1. Evaluation of Computational Method of High Reynolds Number Slurry Flow for Caverns Backfilling

    SciTech Connect

    Bettin, Giorgia

    2015-05-01

    The abandonment of salt caverns used for brining or product storage poses a significant environmental and economic risk. Risk mitigation can in part be address ed by the process of backfilling which can improve the cavern geomechanical stability and reduce the risk o f fluid loss to the environment. This study evaluate s a currently available computational tool , Barracuda, to simulate such process es as slurry flow at high Reynolds number with high particle loading . Using Barracuda software, a parametric sequence of simu lations evaluated slurry flow at Re ynolds number up to 15000 and loading up to 25%. Li mitations come into the long time required to run these simulation s due in particular to the mesh size requirement at the jet nozzle. This study has found that slurry - jet width and centerline velocities are functions of Re ynold s number and volume fractio n The solid phase was found to spread less than the water - phase with a spreading rate smaller than 1 , dependent on the volume fraction. Particle size distribution does seem to have a large influence on the jet flow development. This study constitutes a first step to understand the behavior of highly loaded slurries and their ultimate application to cavern backfilling.

  2. In vitro and in vivo CT imaging using bismuth sulfide modified with a highly biocompatible Pluronic F127

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Yang, Xiao-Quan; Meng, Yuan-Zheng; Huang, Huan-Huan; Qin, Meng-Yao; Yan, Dong-Mei; Zhao, Yuan-Di; Ma, Zhi-Ya

    2014-07-01

    Probe bismuth sulfide modified with Pluronic F127 (Bi2S3-PF127), which has high biocompatibility and dispersibility, is synthesized using triblock copolymer Pluronic F127 to modify hydrophobic Bi2S3 nanoparticles that are prepared by a hot injection method. TEM results show that most of the probe has a length of about 14.85 ± 1.70 nm and a breadth of about 4.79 ± 0.63 nm. After injected into the tail vein of a mouse, the probe has obvious CT contrast enhancement capability from x-ray CT imaging results. Meanwhile, the probe’s in vivo toxicity is also studied. It is found that hematoxylin and eosin stains of major organs have no change. A biochemical analysis (alanine aminotransferase and aspartate aminotransferase) prove the probe has no adverse effects. The results of a blood analysis (white blood cell count, red blood cell count, hemoglobin, and platelet count) are also normal. The biological distribution of Bi by ICP-AES shows that most of nanoparticles are cleaned out after injection 48 h, and the circulation half-life of the probe is 5.0 h, suggesting that Bi2S3-PF127 has a long circulation and indicating that the Bi2S3-PF127 probe has good biocompatibility and safety.

  3. Unstructured and adaptive mesh generation for high Reynolds number viscous flows

    NASA Technical Reports Server (NTRS)

    Mavriplis, Dimitri J.

    1991-01-01

    A method for generating and adaptively refining a highly stretched unstructured mesh suitable for the computation of high-Reynolds-number viscous flows about arbitrary two-dimensional geometries was developed. The method is based on the Delaunay triangulation of a predetermined set of points and employs a local mapping in order to achieve the high stretching rates required in the boundary-layer and wake regions. The initial mesh-point distribution is determined in a geometry-adaptive manner which clusters points in regions of high curvature and sharp corners. Adaptive mesh refinement is achieved by adding new points in regions of large flow gradients, and locally retriangulating; thus, obviating the need for global mesh regeneration. Initial and adapted meshes about complex multi-element airfoil geometries are shown and compressible flow solutions are computed on these meshes.

  4. Sweep and Compressibility Effects on Active Separation Control at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Seifert, Avi; Pack, LaTunia G.

    2000-01-01

    This paper explores the effects of compressibility, sweep and excitation location on active separation control at high Reynolds numbers. The model, which was tested in a cryogenic pressurized wind tunnel, simulates the upper surface of a 20% thick Glauert Goldschmied type airfoil at zero angle of attack. The flow is fully turbulent since the tunnel sidewall boundary layer flows over the model. Without control, the flow separates at the highly convex area and a large turbulent separation bubble is formed. Periodic excitation is applied to gradually eliminate the separation bubble. Two alternative blowing slot locations as well as the effect of compressibility, sweep and steady suction or blowing were studied. During the test the Reynolds numbers ranged from 2 to 40 million and Mach numbers ranged from 0.2 to 0.7. Sweep angles were 0 and 30 deg. It was found that excitation must be introduced slightly upstream of the separation region regardless of the sweep angle at low Mach number. Introduction of excitation upstream of the shock wave is more effective than at its foot. Compressibility reduces the ability of steady mass transfer and periodic excitation to control the separation bubble but excitation has an effect on the integral parameters, which is similar to that observed in low Mach numbers. The conventional swept flow scaling is valid for fully and even partially attached flow, but different scaling is required for the separated 3D flow. The effectiveness of the active control is not reduced by sweep. Detailed flow field dynamics are described in the accompanying paper.

  5. Urban Town and Gown: Increasing Minority Participation in the Geosciences Through a College-High School Partnership in Hartford, CT

    NASA Astrophysics Data System (ADS)

    OConnell, S.; OConnell, S.; OConnell, S.; Osborn, J. L.; Osborn, J. L.

    2001-12-01

    Urban public schools are often poor and have a tremendous need for educational assistance. In many cities the population is dominated by ethnic minorities. Hartford, CT, is one of these cities. Only about 50% of the students entering high school graduate and approximately 50% of those go on to higher education. Of those students taking the SAT's the average verbal and math scores are below 400. Despite these statistics, many students do succeed and therein lies an opportunity for earth scientists. As individuals and as institutions we can partner with schools and students to involve them in and excite them about the earth sciences. In 1995 Trinity College, located in Hartford, CT, undertook a \\$175 m.d. neighborhood revitalization project with funds from the college, neighboring institutions, foundations, and city, state and federal governments. Central to the revitalization is the "Learning Corridor," an educational complex that includes a magnet Montessori School, a Math and Science Middle School, and a Math and Science Magnet High School (GHAMAS). GHAMAS has a three-fold mission: teaching math and science to high school students, professional development for all math and science teachers from participating school districts, and community outreach. The Learning Corridor is adjacent to the Trinity College campus and Trinity faculty work with GHAMAS faculty to fulfill all three missions. Trinity faculty teach several high school classes. During the summer 3 Trinity and 1 GHAMAS faculty participated as a group in a week long-long NSF-sponsored Environmental Science workshop. This fall over ten teacher workshops were co-taught by Trinity and GHAMAS faculty. Recent NSF funding will allow us to develop a collaborative education and research program focused on the Connecticut River.

  6. Head CT scan

    MedlinePlus

    Brain CT; Cranial CT; CT scan - skull; CT scan - head; CT scan - orbits; CT scan - sinuses; Computed tomography - cranial ... or other growth (mass) Cerebral atrophy (loss of brain tissue) ... with the hearing nerve Stroke or transient ischemic attack (TIA)

  7. Prohibitin Expression Deregulation in Gastric Cancer Is Associated with the 3′ Untranslated Region 1630 C>T Polymorphism and Copy Number Variation

    PubMed Central

    Leal, Mariana Ferreira; Cirilo, Priscila Daniele Ramos; Mazzotti, Tatiane Katsue Furuya; Calcagno, Danielle Queiroz; Wisnieski, Fernanda; Demachki, Samia; Martinez, Margarita Cortes; Assumpção, Paulo Pimentel; Chammas, Roger; Burbano, Rommel Rodríguez; Smith, Marília Cardoso

    2014-01-01

    PHB is a reported oncogene and tumor suppressor in gastric cancer. Here, we evaluated whether the PHB copy number and the rs6917 polymorphism affect its expression in gastric cancer. Down-regulation and up-regulation of PHB were observed in the evaluated tumors. Reduced expression was associated with tumor dedifferentiation and cancer initiation. The T allele of the rs6917 polymorphism was associated with reduced PHB mRNA levels. Moreover, the up-regulation of PHB appeared to be regulated by the gain of additional gene copies. Thus, PHB copy number variation and differential expression of the rs6917 polymorphism may play a role in PHB transcriptional regulation. PMID:24879411

  8. Prohibitin expression deregulation in gastric cancer is associated with the 3' untranslated region 1630 C>T polymorphism and copy number variation.

    PubMed

    Leal, Mariana Ferreira; Cirilo, Priscila Daniele Ramos; Mazzotti, Tatiane Katsue Furuya; Calcagno, Danielle Queiroz; Wisnieski, Fernanda; Demachki, Samia; Martinez, Margarita Cortes; Assumpção, Paulo Pimentel; Chammas, Roger; Burbano, Rommel Rodríguez; Smith, Marília Cardoso

    2014-01-01

    PHB is a reported oncogene and tumor suppressor in gastric cancer. Here, we evaluated whether the PHB copy number and the rs6917 polymorphism affect its expression in gastric cancer. Down-regulation and up-regulation of PHB were observed in the evaluated tumors. Reduced expression was associated with tumor dedifferentiation and cancer initiation. The T allele of the rs6917 polymorphism was associated with reduced PHB mRNA levels. Moreover, the up-regulation of PHB appeared to be regulated by the gain of additional gene copies. Thus, PHB copy number variation and differential expression of the rs6917 polymorphism may play a role in PHB transcriptional regulation. PMID:24879411

  9. Time dependent heat transfer rates in high Reynolds number hypersonic flowfields

    NASA Technical Reports Server (NTRS)

    Flanagan, Michael J.

    1992-01-01

    Time dependent heat transfer rates have been calculated from time dependent temperature measurements in the vicinity of shock-wave boundary-layer interactions due to conical compression ramps on an axisymmetric body. The basic model is a cylindrical body with a 10 degree conical nose. Four conical ramps, 20, 25, 30, and 35 degrees serve as shock wave generators. Flowfield surveys have been made in the vicinity of the conical ramp vertex, the separation point, and the reattachment point. A significant effort was made to characterize the natural frequencies and relative powers of the resulting fluctuations in heat transfer rates. This research effort, sponsored jointly by NASA and the Air Force, was conducted in the Air Force Flight Dynamics Directorate High Reynolds Facility. The nominal freestream Mach number was 6, and the freestream Reynolds numbers ranged from 2.2 million/ft to 30.0 million/ft. Experimental results quantify temperature response and the resulting heat transfer rates as a function of ramp angle and Reynolds number. The temperature response within the flowfield appears to be steady-state for all compression ramp angles and all Reynolds numbers, and hence, the heat transfer rates appear to be steady-state.

  10. Accurate and reliable high-throughput detection of copy number variation in the human genome

    PubMed Central

    Fiegler, Heike; Redon, Richard; Andrews, Dan; Scott, Carol; Andrews, Robert; Carder, Carol; Clark, Richard; Dovey, Oliver; Ellis, Peter; Feuk, Lars; French, Lisa; Hunt, Paul; Kalaitzopoulos, Dimitrios; Larkin, James; Montgomery, Lyndal; Perry, George H.; Plumb, Bob W.; Porter, Keith; Rigby, Rachel E.; Rigler, Diane; Valsesia, Armand; Langford, Cordelia; Humphray, Sean J.; Scherer, Stephen W.; Lee, Charles; Hurles, Matthew E.; Carter, Nigel P.

    2006-01-01

    This study describes a new tool for accurate and reliable high-throughput detection of copy number variation in the human genome. We have constructed a large-insert clone DNA microarray covering the entire human genome in tiling path resolution that we have used to identify copy number variation in human populations. Crucial to this study has been the development of a robust array platform and analytic process for the automated identification of copy number variants (CNVs). The array consists of 26,574 clones covering 93.7% of euchromatic regions. Clones were selected primarily from the published “Golden Path,” and mapping was confirmed by fingerprinting and BAC-end sequencing. Array performance was extensively tested by a series of validation assays. These included determining the hybridization characteristics of each individual clone on the array by chromosome-specific add-in experiments. Estimation of data reproducibility and false-positive/negative rates was carried out using self–self hybridizations, replicate experiments, and independent validations of CNVs. Based on these studies, we developed a variance-based automatic copy number detection analysis process (CNVfinder) and have demonstrated its robustness by comparison with the SW-ARRAY method. PMID:17122085

  11. Reduced numbers of switched memory B cells with high terminal differentiation potential in Down syndrome

    PubMed Central

    Carsetti, Rita; Valentini, Diletta; Marcellini, Valentina; Scarsella, Marco; Marasco, Emiliano; Giustini, Ferruccio; Bartuli, Andrea; Villani, Alberto; Ugazio, Alberto G

    2015-01-01

    Children with Down syndrome (DS) have increased susceptibility to infections and a high frequency of leukemia and autoimmune disorders, suggesting that immunodeficiency and immune dysfunction are integral parts of the syndrome. A reduction in B-cell numbers has been reported, associated with moderate immunodeficiency and normal immunoglobulin levels. Here, we compared B-cell populations of 19 children with DS with those in healthy age-matched controls. We found that all steps of peripheral B-cell development are altered in DS, with a more severe defect during the later stages of B-cell development. Transitional and mature-naïve B-cell numbers are reduced by 50% whereas switched memory B cells represent 10–15% of the numbers in age-matched controls. Serum IgM levels were slightly reduced, but all other immunoglobulin isotypes were in the normal range. The frequency of switched memory B cells specific for vaccine antigens was significantly lower in affected children than in their equivalently vaccinated siblings. In vitro switched memory B cells of patients with DS have an increased ability to differentiate into antibody-forming cells in response to TLR9 signals. Tailored vaccination schedules increasing the number of switched memory B cells may improve protection and reduce the risk of death from infection in DS. PMID:25472482

  12. High-Reynolds Number Circulation Control Testing in the National Transonic Facility

    NASA Technical Reports Server (NTRS)

    Milholen, William E., II; Jones, Gregory S.; Chan, David T.; Goodliff, Scott L.

    2012-01-01

    A new capability to test active flow control concepts and propulsion simulations at high Reynolds numbers in the National Transonic Facility at the NASA Langley Research Center is being developed. The first active flow control experiment was completed using the new FAST-MAC semi-span model to study Reynolds number scaling effects for several circulation control concepts. Testing was conducted over a wide range of Mach numbers, up to chord Reynolds numbers of 30 million. The model was equipped with four onboard flow control valves allowing independent control of the circulation control plenums, which were directed over a 15% chord simple-hinged flap. Preliminary analysis of the uncorrected lift data showed that the circulation control increased the low-speed maximum lift coefficient by 33%. At transonic speeds, the circulation control was capable of positively altering the shockwave pattern on the upper wing surface and reducing flow separation. Furthermore, application of the technique to only the outboard portion of the wing demonstrated the feasibility of a pneumatic based roll control capability.

  13. A study of high-lift airfoils at high Reynolds numbers in the Langley low-turbulence pressure tunnel

    NASA Technical Reports Server (NTRS)

    Morgan, Harry L., Jr.; Ferris, James C.; Mcghee, Robert J.

    1987-01-01

    An experimental study was conducted in the Langley Low Turbulence Pressure Tunnel to determine the effects of Reynolds number and Mach number on the two-dimensional aerodynamic performance of two supercritical type airfoils, one equipped with a conventional flap system and the other with an advanced high lift flap system. The conventional flap system consisted of a leading edge slat and a double slotted, trailing edge flap with a small chord vane and a large chord aft flap. The advanced flap system consisted of a leading edge slat and a double slotted, trailing edge flap with a large chord vane and a small chord aft flap. Both models were tested with all elements nested to form the cruise airfoil and with the leading edge slat and with a single or double slotted, trailing edge flap deflected to form the high lift airfoils. The experimental tests were conducted through a Reynolds number range from 2.8 to 20.9 x 1,000,000 and a Mach number range from 0.10 to 0.35. Lift and pitching moment data were obtained. Summaries of the test results obtained are presented and comparisons are made between the observed aerodynamic performance trends for both models. The results showing the effect of leading edge frost and glaze ice formation is given.

  14. Low-dose coronary-CT angiography using step and shoot at any heart rate: comparison of image quality at systole for high heart rate and diastole for low heart rate with a 128-slice dual-source machine.

    PubMed

    Paul, Jean-François; Amato, Aude; Rohnean, Adela

    2013-03-01

    To compare image quality of coronary CT angiography in step-and-shoot mode at the diastolic phase at low heart rates (<70 bpm) and systolic phase at high heart rates (≥70 bpm). We prospectively included 96 consecutive patients then excluded 5 patients with arrhythmia. Coronary CT-angiography was performed using a dual-source 128-slice CT machine, at the diastolic phase in the 55 patients with heart rates <70 bpm (group D) and at the systolic phase in the 36 patients with heart rates ≥70 (group S). Image quality was scored on a 5 point-scale (1, not interpretable; 2, insufficient for diagnosis; 3, fair, sufficient for diagnosis; 4, good; 5, excellent). In addition, we compared the number of stair-step artifacts in the two groups. Mean image quality score was 4 (0.78) in group D and 4.1 (0.34) in group S (NS), with an unequal distribution (p = 0.01). Step artifacts were seen in 44 % of group D and 18 % of group S patients (p = 0.02). In 3 group D patients and no group S patients, the image score was <3 due to artifacts, requiring repeat CT-angiography. When performing dual-source 128-slice CT-angiography, step-and-shoot acquisition provides comparable mean image quality in systole, with less variability and fewer stair-step artifacts, compared to diastole. This method may be feasible at any heart rate in most patients in sinus rhythm, allowing low-dose prospective acquisition without beta-blocker premedication. PMID:22918571

  15. Fast response temperature and humidity sensors for measurements in high Reynolds number flows

    NASA Astrophysics Data System (ADS)

    Fan, Yuyang; Arwatz, Gilad; Vallikivi, Margit; Hultmark, Marcus

    2013-11-01

    Conventional hot/cold wires have been widely used in measuring velocity and temperature in turbulent flows due to their fine resolutions and fast response. However, for very high Reynolds number flows, limitations on the resolution appear. A very high Reynolds number flow is the atmospheric boundary layer. In order to accurately predict the energy balance at the Earth's surface, one needs information about the different turbulent scalar fields, mainly temperature and humidity, which together with velocity, contribute to the turbulent fluxes away from the surface. The nano-scaled thermal anemometry probe (NSTAP) was previously developed at Princeton and has proven to have much higher spatial and temporal resolution than the regular hot wires. Here we introduce new fast-response temperature and humidity sensors that have been developed and tested. These sensors are made in-house using standard MEMS manufacturing techniques, leaving high flexibility in the process for optimization to different conditions. The small dimensions of these novel sensors enable very high spatial resolution while the small thermal mass allows significant improvements in the frequency response. These sensors have shown promising results in acquiring un-biased data of turbulent scalar and vector fields. Supported under ONR Grants N00014-12-1-0875 and N00014-12-1-0962 (program manager Ki-Han Kim).

  16. Universality of spectrum of passive scalar variance at very high Schmidt number in isotropic steady turbulence

    NASA Astrophysics Data System (ADS)

    Gotoh, Toshiyuki

    2012-11-01

    Spectrum of passive scalar variance at very high Schmidt number up to 1000 in isotropic steady turbulence has been studied by using very high resolution DNS. Gaussian random force and scalar source which are isotropic and white in time are applied at low wavenumber band. Since the Schmidt number is very large, the system was integrated for 72 large eddy turn over time for the system to forgot the initial state. It is found that the scalar spectrum attains the asymptotic k-1 spectrum in the viscous-convective range and the constant CB is found to be 5.7 which is larger than 4.9 obtained by DNS under the uniform mean scalar gradient. Reasons for the difference are inferred as the Reynolds number effect, anisotropy, difference in the scalar injection, duration of time average, and the universality of the constant is discussed. The constant CB is also compared with the prediction by the Lagrangian statistical theory for the passive scalar. The scalar spectrum in the far diffusive range is found to be exponential, which is consistent with the Kraichnan's spectrum. However, the Kraichnan spectrum was derived under the assumption that the velocity field is white in time, therefore theoretical explanation of the agreement needs to be explored. Grant-in-Aid for Scientific Research No. 21360082, Ministry of Education, Culture, Sports, Science and Technology of Japan.

  17. High-Resolution Micro-CT for Morphologic and Quantitative Assessment of the Sinusoid in Human Cavernous Hemangioma of the Liver

    PubMed Central

    Duan, Jinghao; Hu, Chunhong; Chen, Hua

    2013-01-01

    Hepatic sinusoid plays a vital role in human cavernous hemangioma of the liver (CHL), and its morphologic investigation facilitates the understanding of microcirculation mechanism and pathological change of CHL. However, precise anatomical view of the hepatic sinusoid has been limited by the resolution and contrast available from existing imaging techniques. While liver biopsy has traditionally been the reliable method for the assessment of hepatic sinusoids, the invasiveness and sampling error are its inherent limitations. In this study, imaging of CHL samples was performed using in-line phase-contrast imaging (ILPCI) technique with synchrotron radiation. ILPCI allowed clear visualization of soft tissues and revealed structural details that were invisible to conventional radiography. Combining the computed tomography (CT) technique, ILPCI-CT was used to acquire the high-resolution micro-CT images of CHL, and three dimensional (3D) microstructures of hepatic sinusoids were provided for the morphologic depiction and quantitative assessment. Our study demonstrated that ILPCI-CT could substantially improve the radiographic contrast of CHL tissues in vitro with no contrast agent. ILPCI-CT yielded high-resolution micro-CT image of CHL sample at the micron scale, corresponding to information on actual structures revealed at histological section. The 3D visualization provided an excellent view of the hepatic sinusoid. The accurate view of individual hepatic sinusoid was achieved. The valuable morphological parameters of hepatic sinusoids, such as thrombi, diameters, surface areas and volumes, were measured. These parameters were of great importance in the evaluation of CHL, and they provided quantitative descriptors that characterized anatomical properties and pathological features of hepatic sinusoids. The results highlight the high degree of sensitivity of the ILPCI-CT technique and demonstrate the feasibility of accurate visualization of hepatic sinusoids. Moreover

  18. Soft tissue visualization using a highly efficient megavoltage cone beam CT imaging system

    NASA Astrophysics Data System (ADS)

    Ghelmansarai, Farhad A.; Bani-Hashemi, Ali; Pouliot, Jean; Calderon, Ed; Hernandez, Paco; Mitschke, Matthias; Aubin, Michelle; Bucci, Kara

    2005-04-01

    Recent developments in two-dimensional x-ray detector technology have made volumetric Cone Beam CT (CBCT) a feasible approach for integration with conventional medical linear accelerators. The requirements of a robust image guidance system for radiation therapy include the challenging combination of soft tissue sensitivity with clinically reasonable doses. The low contrast objects may not be perceptible with MV energies due to the relatively poor signal to noise ratio (SNR) performance. We have developed an imaging system that is optimized for MV and can acquire Megavoltage CBCT images containing soft tissue contrast using a 6MV x-ray beam. This system is capable of resolving relative electron density as low as 1% with clinically acceptable radiation doses. There are many factors such as image noise, x-ray scatter, improper calibration and acquisitions that have a profound effect on the imaging performance of CBCT and in this study attempts were made to optimize these factors in order to maximize the SNR. A QC-3V phantom was used to determine the contrast to noise ratio (CNR) and f50 of a single 2-D projection. The computed f50 was 0.43 lp/mm and the CNR for a radiation dose of 0.02cGy was 43. Clinical Megavoltage CBCT images acquired with this system demonstrate that anatomical structures such as the prostate in a relatively large size patient are visible using radiation doses in range of 6 to 8cGy.

  19. High-speed quantum-random number generation by continuous measurement of arrival time of photons

    SciTech Connect

    Yan, Qiurong; Zhao, Baosheng; Hua, Zhang; Liao, Qinghong; Yang, Hao

    2015-07-15

    We demonstrate a novel high speed and multi-bit optical quantum random number generator by continuously measuring arrival time of photons with a common starting point. To obtain the unbiased and post-processing free random bits, the measured photon arrival time is converted into the sum of integral multiple of a fixed period and a phase time. Theoretical and experimental results show that the phase time is an independent and uniform random variable. A random bit extraction method by encoding the phase time is proposed. An experimental setup has been built and the unbiased random bit generation rate could reach 128 Mb/s, with random bit generation efficiency of 8 bits per detected photon. The random numbers passed all tests in the statistical test suite.

  20. High-speed quantum-random number generation by continuous measurement of arrival time of photons.

    PubMed

    Yan, Qiurong; Zhao, Baosheng; Hua, Zhang; Liao, Qinghong; Yang, Hao

    2015-07-01

    We demonstrate a novel high speed and multi-bit optical quantum random number generator by continuously measuring arrival time of photons with a common starting point. To obtain the unbiased and post-processing free random bits, the measured photon arrival time is converted into the sum of integral multiple of a fixed period and a phase time. Theoretical and experimental results show that the phase time is an independent and uniform random variable. A random bit extraction method by encoding the phase time is proposed. An experimental setup has been built and the unbiased random bit generation rate could reach 128 Mb/s, with random bit generation efficiency of 8 bits per detected photon. The random numbers passed all tests in the statistical test suite. PMID:26233362

  1. Large-scale magnetic fields at high Reynolds numbers in magnetohydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Hotta, H.; Rempel, M.; Yokoyama, T.

    2016-03-01

    The 11-year solar magnetic cycle shows a high degree of coherence in spite of the turbulent nature of the solar convection zone. It has been found in recent high-resolution magnetohydrodynamics simulations that the maintenance of a large-scale coherent magnetic field is difficult with small viscosity and magnetic diffusivity (≲1012square centimenters per second). We reproduced previous findings that indicate a reduction of the energy in the large-scale magnetic field for lower diffusivities and demonstrate the recovery of the global-scale magnetic field using unprecedentedly high resolution. We found an efficient small-scale dynamo that suppresses small-scale flows, which mimics the properties of large diffusivity. As a result, the global-scale magnetic field is maintained even in the regime of small diffusivities—that is, large Reynolds numbers.

  2. Large-scale magnetic fields at high Reynolds numbers in magnetohydrodynamic simulations.

    PubMed

    Hotta, H; Rempel, M; Yokoyama, T

    2016-03-25

    The 11-year solar magnetic cycle shows a high degree of coherence in spite of the turbulent nature of the solar convection zone. It has been found in recent high-resolution magnetohydrodynamics simulations that the maintenance of a large-scale coherent magnetic field is difficult with small viscosity and magnetic diffusivity (≲10 (12) square centimenters per second). We reproduced previous findings that indicate a reduction of the energy in the large-scale magnetic field for lower diffusivities and demonstrate the recovery of the global-scale magnetic field using unprecedentedly high resolution. We found an efficient small-scale dynamo that suppresses small-scale flows, which mimics the properties of large diffusivity. As a result, the global-scale magnetic field is maintained even in the regime of small diffusivities-that is, large Reynolds numbers. PMID:27013727

  3. Boundary layer Reynolds stress composition at high and low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Priyadarshana, Paththage; Klewicki, Joseph

    2003-11-01

    Properties of the motions contributing to the Reynolds stresses (-\\overlineuv) in high and low Reynolds number (R_θ) turbulent boundary layers are studied through physical experiments. The low R_θ measurements (R_θ = 2870) were acquired in a laboratory wind tunnel, while the high R_θ data (R_θ ≃ 5 × 10^6) were acquired at the SLTEST site, Utah. At each R_θ, comparisons are made at yp / 2 and 2y_p, where yp is the peak position of -\\overlineuv. Scale separation effects associated with increasing R_θ are analyzed via spectra, and by using high and low-pass filtering. The predominant motions underlying the stress undergo a significant shift from large to intermediate scales as R_θ becomes large. Specifically, the peak in the u-v cospectrum is close to the peak in the u power spectrum at low R_θ but shifts to near the peak in the v power spectrum at high R_θ. The low R_θ fractional quadrant -\\overlineuv contributions agree well with published results. High R_θ effects are observed in the fractional contributions through an increase in their magnitudes in each quadrant. Near the wall, an increase in outward interactions is observed at high R_θ. Overall, the contributions to -\\overlineuv are shown to undergo significant variations at comparable wall normal locations (relative to y_p) at the two Reynolds numbers. This work was supported by the Office of Naval Research, grant monitor R. Joslin.

  4. SU-D-207-06: Clinical Validations of Shading Correction for Cone-Beam CT Using Planning CT as a Prior

    SciTech Connect

    Tsui, T; Zhu, L; Wei, J

    2015-06-15

    Purpose: Current cone-beam CT (CBCT) images contain severe shading artifacts mainly due to scatter, hindering their quantitative use in current radiation therapy. We have previously proposed an effective shading correction method for CBCT using planning CT (pCT) as prior knowledge. In this work, we investigate the method robustness via statistical analyses on studies of a large patient group and compare the performance with that of a state-of-the-art method implemented on the current commercial radiation therapy machine -- the Varian Truebeam system. Methods: Since radiotherapy patients routinely undergo multiple-detector CT (MDCT) scans in the planning procedure, we use the high-quality pCT as “free” prior knowledge for CBCT image improvement. The CBCT image with no correction is first spatially registered with the pCT. Primary CBCT projections are estimated via forward projections of the registered image. The low frequency errors in the projections, which stem from mainly scatter, are estimated by filtering the difference between original line integral and the estimated scatter projections. The corrected CBCT image is then reconstructed from the scatter corrected projections. The proposed method is evaluated on 40 cancer patients. Results: On all patient images, we compare errors on CT number, spatial non-uniformity (SNU) and image contrast, using pCT as the ground truth. T-tests show that our algorithm improves over the Varian method on CBCT accuracies of CT number and SNU with 90% confident. The average CT number error is reduced from 54.8 HU on the Varian method to 40.9 HU, and the SNU error is reduced from 7.7% to 3.8%. There is no obvious improvement on image contrast. Conclusion: Large-group patient studies show that the proposed pCT-based algorithm outperforms the Varian method of the Truebeam system on CBCT shading correction, by providing CBCT images with higher CT number accuracy and greater image uniformity.

  5. Turbulent mixing due to Holmboe wave instability in stratified shear flows at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Salehipour, Hesam; Caulfield, Colm-Cille; Peltier, W. Richard

    2015-11-01

    We consider numerically the transition to turbulence and associated mixing in parallel stratified shear flows with hyperbolic tangent initial velocity and density distributions. When the characteristic length scale of density variation is sufficiently sharper than that of the velocity variation, this flow is primarily susceptible to Holmboe wave instability (HWI) which perturbs the interface to exhibit characteristic cusped interfacial waves. Unlike previous low- Re experimental and numerical studies, in the high- Re regime in which our DNS analyses are performed, the primary HWI triggers a vigorous yet markedly more long-lived turbulent event compared to its better known relative, the Kelvin-Helmholtz instability (KHI). HWI `scours' the primary density interface, leading to substantial irreversible mixing and vertical transport of density displaced above and below the (robust) primary density interface which is comparable in both absolute terms and relative efficiency to the mixing associated with an equivalent KHI. Our results establish categorically that, provided the Reynolds number is high enough, shear layers with sharp density interfaces and associated locally high values of the gradient Richardson number are sites of substantial and efficient irreversible mixing. H.S. is grateful to the David Crighton Fellowship from DAMTP, University of Cambridge.

  6. Aerosol formation from high-velocity uranium drops: Comparison of number and mass distributions. Final report

    SciTech Connect

    Rader, D.J.; Benson, D.A.

    1995-05-01

    This report presents the results of an experimental study of the aerosol produced by the combustion of high-velocity molten-uranium droplets produced by the simultaneous heating and electromagnetic launch of uranium wires. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. As reported earlier, the resulting aerosol consists mainly of web-like chain agglomerates. A condensation nucleus counter was used to investigate the decay of the total particle concentration due to coagulation and losses. Number size distributions based on mobility equivalent diameter obtained soon after launch with a Differential Mobility Particle Sizer showed lognormal distributions with an initial count median diameter (CMD) of 0.3 {mu}m and a geometric standard deviation, {sigma}{sub g} of about 2; the CMD was found to increase and {sigma}{sub g} decrease with time due to coagulation. Mass size distributions based on aerodynamic diameter were obtained for the first time with a Microorifice Uniform Deposit Impactor, which showed lognormal distributions with mass median aerodynamic diameters of about 0.5 {mu}m and an aerodynamic geometric standard deviation of about 2. Approximate methods for converting between number and mass distributions and between mobility and aerodynamic equivalent diameters are presented.

  7. Experimental investigation of acoustic streaming in a cylindrical wave guide up to high streaming Reynolds numbers.

    PubMed

    Reyt, Ida; Bailliet, Hélène; Valière, Jean-Christophe

    2014-01-01

    Measurements of streaming velocity are performed by means of Laser Doppler Velocimetry and Particle Image Velociimetry in an experimental apparatus consisting of a cylindrical waveguide having one loudspeaker at each end for high intensity sound levels. The case of high nonlinear Reynolds number ReNL is particularly investigated. The variation of axial streaming velocity with respect to the axial and to the transverse coordinates are compared to available Rayleigh streaming theory. As expected, the measured streaming velocity agrees well with the Rayleigh streaming theory for small ReNL but deviates significantly from such predictions for high ReNL. When the nonlinear Reynolds number is increased, the outer centerline axial streaming velocity gets distorted towards the acoustic velocity nodes until counter-rotating additional vortices are generated near the acoustic velocity antinodes. This kind of behavior is followed by outer streaming cells only and measurements in the near wall region show that inner streaming vortices are less affected by this substantial evolution of fast streaming pattern. Measurements of the transient evolution of streaming velocity provide an additional insight into the evolution of fast streaming. PMID:24437742

  8. Rayleigh-Bénard convection at high Prandtl numbers in circular and square geometry

    NASA Astrophysics Data System (ADS)

    Johnston, Stephen R.; Fonda, Enrico; Sreenivasan, Katepalli R.; Ranjan, Devesh

    2015-11-01

    Experiments using water and simulations have shown that flow structures and turbulent fluctuations in Rayleigh-Bénard convection are affected by the shape of the container. We study the effect of the geometry in both square and cylindrical test cells of aspect ratio of order unity in high Prandtl fluids (up to 104). Flow visualization using a photochromic dye seeded throughout the fluid allows us to uninvasively study the evolution of the large scale structures. We discuss the observations in the two geometries and compare them with previous observations at low Prandtl numbers.

  9. A high-Reynolds-number seal test facility: Facility description and preliminary test data

    NASA Technical Reports Server (NTRS)

    Childs, D. W.; Nelson, C.; Noyes, T.; Dressman, J. B.

    1982-01-01

    A facility has been developed for testing the leakage and rotordynamic characteristics of interstage-seal configurations for the HPFTP (High Pressure Fuel Turbopump) of the SSME (Space Shuttle Main Engine). Axial Reynolds numbers on the order of 400,000 are realized in the test facility by using a Dupont freon fluid called Halon (CBrF3). The kinematic viscosity of Halon is of the same order as the liquid hydrogen used in the HPFTP. Initial testing has focused on the current flight configurations (a three-segment, stepped unit) and a convergent-taper candidate.

  10. A parameter identification method for the rotordynamic coefficients of a high Reynolds number hydrostatic bearing

    NASA Technical Reports Server (NTRS)

    Rouvas, C.; Childs, D. W.

    1993-01-01

    In identifying the rotordynamic coefficients of a high-Reynolds-number hydrostatic bearing, fluid-flow induced forces present a unique problem, in that they provide an unmeasureable and uncontrollable excitation to the bearing. An analysis method is developed that effectively eliminates the effects of fluid-flow induced excitation on the estimation of the bearing rotordynamic coefficients, by using power spectral densities. In addition to the theoretical development, the method is verified experimentally by single-frequency testing, and repeatability tests. Results obtained for a bearing are the twelve rotordynamic coefficients (stiffness, damping, and inertia coefficients) as functions of eccentricity ratio, speed, and supply pressure.

  11. A high-copy-number CACTA family transposon in temperate grasses and cereals.

    PubMed Central

    Langdon, Tim; Jenkins, Glyn; Hasterok, Robert; Jones, R Neil; King, Ian P

    2003-01-01

    A lineage of CACTA family transposons has been identified in temperate grasses and cereals, and a full-length representative of the subfamily from Lolium perenne has been sequenced. Both the size and internal organization of the L. perenne element are typical of other CACTA family elements but its high copy number and strong conservation are unexpected. Comparison with homologs in other species suggests that this lineage has adopted a distinct and novel evolutionary strategy, which has allowed it to maintain its presence in genomes over long periods of time. PMID:12663547

  12. The role of early 18F-FDG PET/CT in therapeutic management and ongoing risk stratification of high/intermediate-risk thyroid carcinoma.

    PubMed

    Triviño Ibáñez, E M; Muros, M A; Torres Vela, E; Llamas Elvira, J M

    2016-03-01

    Little is known about the role in ongoing risk stratification of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) performed early after radioactive iodine (RAI) ablation in differentiated thyroid carcinoma (DTC). The aim of the study is to investigate whether 18F-FDG PET/CT performed early after RAI ablation is useful to detect disease and to influence therapy and ongoing risk stratification. Patients with high/intermediate risk of recurrent DTC were included. 18F-FDG PET/CT scan was performed within 6 months after RAI ablation. We confirmed results with other imaging techniques, pathology reports, or follow-up. We classified the patient response as excellent, acceptable, or incomplete. Modified Hicks criteria were used to evaluate clinical impact. We included 81 patients with high/intermediate risk of recurrent DTC. Forty-one (50.6 %) had positive uptake in 18F-FDG PET/CT, with negative (131)I whole-body scan ((131)I WBS). Sensitivity, specificity, and diagnostic accuracy of 18F-FDG PET/CT were 92.5, 90.2, and 91.4 %, respectively. 18F-FDG PET/CT results had an impact on therapy in 38.3 % of patients. One year after initial therapy, 45.7 % showed excellent response, 8.6 % acceptable response, and 45.7 % incomplete response. A statistically significant relationship was found between negative 18F-FDG PET/CT and excellent response (80 vs. 12.2 %, p < 0.001; OR 52.8). 18F-FDG PET/CT scan performed early in surveillance of patients with high/intermediate-risk thyroid carcinoma provides important additional information not available with conventional follow-up methods and had a high impact on therapy. A negative 18F-FDG PET/CT predicts an excellent response to therapy in the new ongoing risk stratification. PMID:26224589

  13. Characterization of a high-resolution hybrid DOI detector for a dedicated breast PET/CT scanner.

    PubMed

    Godinez, Felipe; Chaudhari, Abhijit J; Yang, Yongfeng; Farrell, Richard; Badawi, Ramsey D

    2012-06-01

    The aim of this study is to design and test a new high-resolution hybrid depth of interaction (DOI) detector for a dedicated breast PET/CT scanner. Two detectors have been designed and built. The completed detectors are based on a 14 × 14 array of 1.5 × 1.5 × 20 mm(3) unpolished lutetium orthosilicate scintillation crystals, with each element coated in a 50 μm layer of reflective material. The detector is read out from both ends using a position-sensitive photomultiplier tube (PSPMT) and a large active area (20 × 20 mm(2)) avalanche photodiode (APD) to enable acquisition of DOI information. Nuclear instrumentation modules were used to characterize the detectors' performances in terms of timing, intrinsic spatial resolution (ISR) and energy resolution, as well as DOI resolution with a dual-ended readout configuration. Measurements with the APD were performed at a temperature of 10 °C. All crystals were identified at all depths, even though the signal amplitude from the PSPMT decreases with depth away from it. We measured a timing resolution of 2.4 ns, and an average energy resolution of 19%. The mean ISR was measured to be 1.2 mm for crystals in the central row of the array for detectors in the face-to-face position. Two off-center positions were measured corresponding to 26° and 51° oblique photon incidence, and the mean ISR at these positions was 1.5 and 1.7 mm, respectively. The average DOI resolution across all crystals and depths was measured to be 2.9 mm (including the beam width of 0.6 mm). This detector design shows good promise as a high-resolution detector for a dedicated breast PET/CT scanner. PMID:22581109

  14. High quantum-efficiency photon-number-resolving detector for photonic on-chip information processing.

    PubMed

    Calkins, Brice; Mennea, Paolo L; Lita, Adriana E; Metcalf, Benjamin J; Kolthammer, W Steven; Lamas-Linares, Antia; Spring, Justin B; Humphreys, Peter C; Mirin, Richard P; Gates, James C; Smith, Peter G R; Walmsley, Ian A; Gerrits, Thomas; Nam, Sae Woo

    2013-09-23

    The integrated optical circuit is a promising architecture for the realization of complex quantum optical states and information networks. One element that is required for many of these applications is a high-efficiency photon detector capable of photon-number discrimination. We present an integrated photonic system in the telecom band at 1550 nm based on UV-written silica-on-silicon waveguides and modified transition-edge sensors capable of number resolution and over 40 % efficiency. Exploiting the mode transmission failure of these devices, we multiplex three detectors in series to demonstrate a combined 79 % ± 2 % detection efficiency with a single pass, and 88 % ± 3 % at the operating wavelength of an on-chip terminal reflection grating. Furthermore, our optical measurements clearly demonstrate no significant unexplained loss in this system due to scattering or reflections. This waveguide and detector design therefore allows the placement of number-resolving single-photon detectors of predictable efficiency at arbitrary locations within a photonic circuit - a capability that offers great potential for many quantum optical applications. PMID:24104153

  15. Development of a high-frequency electronic integrator for photon-number resolving detectors

    NASA Astrophysics Data System (ADS)

    Meier, Kristina; Wayne, Michael; Kwiat, Paul

    2016-05-01

    Efficient photon-number-resolving single-photon detectors are a critical resource for optical quantum information processing, e.g., for realizing deterministic single-photon production. Previously, we have developed Visible Light Photon Counters (VLPCs) that can detect single photons with high quantum efficiency. The detector configuration allows photons to initiate multiple electron avalanches simultaneously, creating a signal with a charge proportional to the number of photons detected. One current obstacle is the extraction of the total charge of each pulse at frequencies ranging from 200 MHz to 20 GHz. The charge of each pulse is proportional to the area under the input signal and so we are currently developing an electronic integrator that, with appropriate signal amplification, will produce an output signal of pulses with heights equal to the integral of the VLPC pulse, thereby fully realizing the photon-number resolving capabilities of these detectors. Finally, we are also studying the use of optical annealing to reduce the detector's dark counts.

  16. Instability of thermocapillary convection in long liquid bridges of high Prandtl number fluids in microgravity

    NASA Astrophysics Data System (ADS)

    Nishino, Koichi; Yano, Taishi; Kawamura, Hiroshi; Matsumoto, Satoshi; Ueno, Ichiro; Ermakov, Michael K.

    2015-06-01

    This paper reports experimental results on the instability of thermocapillary convection in long half-zone liquid bridges of high Prandtl number fluids (Pr=67, 112 and 207 for 5, 10 and 20 cSt silicone oils, respectively). The experiments were carried out in microgravity on the International Space Station, which allowed sufficiently long waiting period for the development of instability. Critical temperature differences were measured for liquid bridges of 30 and 50 mm diameters and up to 62.5 mm length. The resultant critical Marangoni numbers (Mac) were obtained for a wide range of aspect ratio (=height/diameter), AR, up to AR=2.0. Linear stability analyses for Pr=67 were also carried out to obtain numerical data for comparison. The present experimental results for Pr=67 indicate 5.0×1031.25) and they are in good agreement with the present linear stability analysis result. In contrast, the present results are considerably smaller than the previous data (Pr=74) taken in the Space Shuttle experiments. It is shown that this difference is due to the effect of heating rate of the liquid bridge. The data for oscillation frequency and azimuthal mode number are also presented. The non-dimensional oscillation frequencies as well as Mac for Pr=67 have shown a sudden decrease at around AR=1.25, suggesting the bifurcation of neutral stability curves.

  17. DNS/LES Simulations of Separated Flows at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Balakumar, P.

    2015-01-01

    Direct numerical simulations (DNS) and large-eddy simulations (LES) simulations of flow through a periodic channel with a constriction are performed using the dynamic Smagorinsky model at two Reynolds numbers of 2800 and 10595. The LES equations are solved using higher order compact schemes. DNS are performed for the lower Reynolds number case using a fine grid and the data are used to validate the LES results obtained with a coarse and a medium size grid. LES simulations are also performed for the higher Reynolds number case using a coarse and a medium size grid. The results are compared with an existing reference data set. The DNS and LES results agreed well with the reference data. Reynolds stresses, sub-grid eddy viscosity, and the budgets for the turbulent kinetic energy are also presented. It is found that the turbulent fluctuations in the normal and spanwise directions have the same magnitude. The turbulent kinetic energy budget shows that the production peaks near the separation point region and the production to dissipation ratio is very high on the order of five in this region. It is also observed that the production is balanced by the advection, diffusion, and dissipation in the shear layer region. The dominant term is the turbulent diffusion that is about two times the molecular dissipation.

  18. Measurement of High Reynolds Number Near-Field Turbulent Sphere Wakes under Stratified Conditions

    NASA Astrophysics Data System (ADS)

    Kalumuck, Kenneth; Brandt, Alan; Decker, Kirk; Shipley, Kara

    2015-11-01

    To characterize the near-field of a stratified wake at Reynolds numbers, Re = 2 x 105 - 106, experiments were conducted with a large diameter (0.5 m) sphere towed through a thermally stratified fresh water lake. Stratification produced BV frequencies, N, up to 0.07/s (42 cph) resulting in Froude numbers F = U/ND >= 15. The submerged sphere and associated instrumentation including two Acoustic Doppler Velocimeters (ADVs) and an array of fast response thermistors were affixed to a common frame towed over a range of speeds. Three components of the instantaneous wake velocities were obtained simultaneously at two cross-wake locations with the ADVs while density fluctuations were inferred from temperature measurements made by the thermistors. These measurements were used to determine the mean, rms, and spectra of all three components of the turbulent velocity field and density fluctuations at multiple locations. The turbulence power spectra follow the expected -5/3 slope with wavenumber. Existing stratified near-field wake data for spheres are for Re =104 and less, and only a very limited set of data under unstratified conditions exists at these large values of Re. Those data are primarily measurements of the sphere drag, surface pressure distribution, and separation rather than in wake turbulence. Advances in CFD modeling have enabled simulations at these high Reynolds numbers without quantitative data available for validation. Sponsored by ONR Turbulence and Wakes program.

  19. Exponential high-order compact scheme on nonuniform grids for the steady MHD duct flow problems with high Hartmann numbers

    NASA Astrophysics Data System (ADS)

    Zhou, K.; Ni, S. H.; Tian, Z. F.

    2015-11-01

    In this article, we establish an exponential high-order compact (EHOC) difference scheme on non-uniform grids for the solution of the coupled equations representing the steady incompressible, viscous magnetohydrodynamic (MHD) flow through a straight channel of rectangular section. A main advantage of the non-uniform grids-based EHOC scheme is that it could use coarser mesh to capture the details within the computational domain for the MHD flow problems with high Hartmann numbers. Numerical experiments are carried out to validate the performance of the currently proposed scheme. Computation results of the MHD flow in the 2D square-channel problems are presented for Hartmann numbers ranging from 10 to 106. The numerical solutions obtained with the newly developed EHOC scheme are also compared with analytic solutions and numerical results by other available methods in the literature. All of these numerical results demonstrate that the currently proposed scheme is accurate, efficient and robust for the wide range of Hartmann numbers 10 to 106.

  20. (18)F-DOPA PET/CT for assessment of response to induction chemotherapy in a child with high-risk neuroblastoma.

    PubMed

    Piccardo, Arnoldo; Lopci, Egesta; Foppiani, Luca; Morana, Giovanni; Conte, Massimo

    2014-03-01

    Functional imaging plays a crucial role in the assessment of neuroblastoma. The evaluation of response to induction chemotherapy is a cornerstone in scheduling proper treatment management in patients affected by high-risk neuroblastoma. (123)I-metaiodobenzylguanidine has been recognized as the radiopharmaceutical of choice in neuroblastoma assessment. To date, the clinical role of PET/CT in pediatric malignancy is not well established.(18)F-DOPA-PET/CT has been recently used in neuroblastoma, and compared with (123)I-MIBG-scan. Scant new data are available about the role of this tool in the evaluation of treatment response after induction chemotherapy. We investigate the role of (18)F-DOPA-PET/CT in characterizing the response to induction chemotherapy in a child affected by high-risk-neuroblastoma, in whom the rare association of (123)I-MIBG-negative primary tumor and MIBG-positive bone marrow metastases was observed. PMID:24247818

  1. [CrF(O2 C(t) Bu)2 ]9 : Synthesis and Characterization of a Regular Homometallic Ring with an Odd Number of Metal Centers and Electrons.

    PubMed

    Woolfson, Robert J; Timco, Grigore A; Chiesa, Alessandro; Vitorica-Yrezabal, Inigo J; Tuna, Floriana; Guidi, Tatiana; Pavarini, Eva; Santini, Paolo; Carretta, Stefano; Winpenny, Richard E P

    2016-07-25

    The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine-templated self-assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of S=1/2 spin states separated by only 0.1 meV (0.8 cm(-1) ). PMID:27294807

  2. High-fidelity simulations of moving and flexible airfoils at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Visbal, Miguel R.; Gordnier, Raymond E.; Galbraith, Marshall C.

    2009-05-01

    The present paper highlights results derived from the application of a high-fidelity simulation technique to the analysis of low-Reynolds-number transitional flows over moving and flexible canonical configurations motivated by small natural and man-made flyers. This effort addresses three separate fluid dynamic phenomena relevant to small fliers, including: laminar separation and transition over a stationary airfoil, transition effects on the dynamic stall vortex generated by a plunging airfoil, and the effect of flexibility on the flow structure above a membrane airfoil. The specific cases were also selected to permit comparison with available experimental measurements. First, the process of transition on a stationary SD7003 airfoil section over a range of Reynolds numbers and angles of attack is considered. Prior to stall, the flow exhibits a separated shear layer which rolls up into spanwise vortices. These vortices subsequently undergo spanwise instabilities, and ultimately breakdown into fine-scale turbulent structures as the boundary layer reattaches to the airfoil surface. In a time-averaged sense, the flow displays a closed laminar separation bubble which moves upstream and contracts in size with increasing angle of attack for a fixed Reynolds number. For a fixed angle of attack, as the Reynolds number decreases, the laminar separation bubble grows in vertical extent producing a significant increase in drag. For the lowest Reynolds number considered ( Re c = 104), transition does not occur over the airfoil at moderate angles of attack prior to stall. Next, the impact of a prescribed high-frequency small-amplitude plunging motion on the transitional flow over the SD7003 airfoil is investigated. The motion-induced high angle of attack results in unsteady separation in the leading edge and in the formation of dynamic-stall-like vortices which convect downstream close to the airfoil. At the lowest value of Reynolds number ( Re c = 104), transition effects are

  3. High-fidelity simulations of moving and flexible airfoils at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Visbal, Miguel R.; Gordnier, Raymond E.; Galbraith, Marshall C.

    The present paper highlights results derived from the application of a high-fidelity simulation technique to the analysis of low-Reynolds-number transitional flows over moving and flexible canonical configurations motivated by small natural and man-made flyers. This effort addresses three separate fluid dynamic phenomena relevant to small fliers, including: laminar separation and transition over a stationary airfoil, transition effects on the dynamic stall vortex generated by a plunging airfoil, and the effect of flexibility on the flow structure above a membrane airfoil. The specific cases were also selected to permit comparison with available experimental measurements. First, the process of transition on a stationary SD7003 airfoil section over a range of Reynolds numbers and angles of attack is considered. Prior to stall, the flow exhibits a separated shear layer which rolls up into spanwise vortices. These vortices subsequently undergo spanwise instabilities, and ultimately breakdown into fine-scale turbulent structures as the boundary layer reattaches to the airfoil surface. In a timeaveraged sense, the flow displays a closed laminar separation bubble which moves upstream and contracts in size with increasing angle of attack for a fixed Reynolds number. For a fixed angle of attack, as the Reynolds number decreases, the laminar separation bubble grows in vertical extent producing a significant increase in drag. For the lowest Reynolds number considered (Re_c = 10^4), transition does not occur over the airfoil at moderate angles of attack prior to stall. Next, the impact of a prescribed high-frequency small-amplitude plunging motion on the transitional flow over the SD7003 airfoil is investigated. The motioninduced high angle of attack results in unsteady separation in the leading edge and in the formation of dynamic-stalllike vortices which convect downstream close to the airfoil. At the lowest value of Reynolds number (Re_c = 10^4), transition effects are

  4. Stark broadening of high-principal-quantum-number n-alpha lines of hydrogen.

    NASA Technical Reports Server (NTRS)

    Lasalle, T. R.; Nee, T.-J.; Griem, H. R.

    1973-01-01

    High n-alpha lines (transitions n + 1 to n) with quantum numbers n between 50 and 250 have been observed emanating from galactic H II regions where the electron density and temperature are about 1000/cu cm and 1 eV, respectively. High n-alpha lines have not previously been seen in the laboratory where fairly homogeneous plasmas may be produced and relatively precise measurements of electron densities and temperatures can be made. The present work describes experiments where the first members of the hydrogen line series with lower states n = 10, 11, 12, and 13 have been detected in a laboratory plasma. The width of the 12-alpha line at 88.7 microns could be measured and was consistent with calculated broadening from elastic electron collisions and quasi-static ion effects.

  5. On large-scale dynamo action at high magnetic Reynolds number

    SciTech Connect

    Cattaneo, F.; Tobias, S. M.

    2014-07-01

    We consider the generation of magnetic activity—dynamo waves—in the astrophysical limit of very large magnetic Reynolds number. We consider kinematic dynamo action for a system consisting of helical flow and large-scale shear. We demonstrate that large-scale dynamo waves persist at high Rm if the helical flow is characterized by a narrow band of spatial scales and the shear is large enough. However, for a wide band of scales the dynamo becomes small scale with a further increase of Rm, with dynamo waves re-emerging only if the shear is then increased. We show that at high Rm, the key effect of the shear is to suppress small-scale dynamo action, allowing large-scale dynamo action to be observed. We conjecture that this supports a general 'suppression principle'—large-scale dynamo action can only be observed if there is a mechanism that suppresses the small-scale fluctuations.

  6. High Reynolds Number Hybrid Laminar Flow Control (HLFC) Flight Experiment. Report 2; Aerodynamic Design

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This document describes the aerodynamic design of an experimental hybrid laminar flow control (HLFC) wing panel intended for use on a Boeing 757 airplane to provide a facility for flight research on high Reynolds number HLFC and to demonstrate practical HLFC operation on a full-scale commercial transport airplane. The design consists of revised wing leading edge contour designed to produce a pressure distribution favorable to laminar flow, definition of suction flow requirements to laminarize the boundary layer, provisions at the inboard end of the test panel to prevent attachment-line boundary layer transition, and a Krueger leading edge flap that serves both as a high lift device and as a shield to prevent insect accretion on the leading edge when the airplane is taking off or landing.

  7. Opposing shear-induced forces dominate inertial focusing in curved channels and high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Keinan, Eliezer; Ezra, Elishai; Nahmias, Yaakov

    2015-11-01

    Inertial focusing is the migration of particles in fluid toward equilibrium, where current theory predicts that shear-induced and wall-induced lift forces are balanced. First reported in 1961, this Segre-Silberberg effect is particularly useful for microfluidic isolation of cells and particles. Interestingly, recent work demonstrated particle focusing at high Reynolds numbers that cannot be explained by current theory. In this work, we show that non-monotonous velocity profiles, such as those developed in curved channels, create peripheral velocity maxima in which opposing shear-induced forces dominate over wall effects. Similarly, entry effects amplified in high Reynolds flow produce an equivalent trapping mechanism in short, straight channels. This focusing mechanism in the developing flow regime enables a 10-fold miniaturization of inertial focusing devices, while our model corrects long-standing misconceptions about the nature of mechanical forces governing inertial focusing in curved channels.

  8. Simulation study of magnetic reconnection in high magnetic Reynolds number plasmas

    NASA Astrophysics Data System (ADS)

    Nakabo, T.; Kusano, K.; Miyoshi, T.; Vekstein, G.

    2013-12-01

    Magnetic reconnection is an important process for dynamics in space and laboratory plasmas. Magnetic reconnection is basically dominated by magnetic diffusion at thin current sheet as proposed by Sweet (1958) and Parker (1963). According to their theory, the reconnection rate must be inversely proportional to the square root of the magnetic Reynolds number (S). In magnetosphere and the solar corona, however, in spite of high magnetic Reynolds number (>10^12), reconnection rate is measured to be about 10^-2 that is much higher than the Sweet and Parker's prediction. Although Petschek proposed that the slow mode shock may accelerate reconnection, numerical simulations suggested that the Petschek's type reconnection cannot be sustained with uniform resistivity. On the other hand, it is pointed out that in high magnetic Reynolds number, the thin current sheet becomes unstable to the so-called secondary tearing instability, which generates many plasmoids and drives a sort of fast reconnection. Although Baty (2012) recently investigated the possibility of Petschek-like structure in relatively high-S (~10^4) regime, it is still unclear whether and how the magnetic reconnection is able to be accelerated in higher-S regime (S>10^5). In this paper, we developed the high-resolution magnetohydrodynamics (MHD) simulation of magnetic reconnection for very high-S (S~10^4-10^6) aiming at revealing the acceleration mechanism of magnetic reconnection. We applied the HLLD Riemann solver, which was developed by Miyoshi and Kusano (2005), to the high resolution two-dimensional MHD simulation of current sheet dynamics. In our model, the initial state is given by the Harris sheet equilibrium plus perturbation. As a result, in the case for S=10^5, multiple X-line reconnection appears as a result of the secondary tearing instability and magnetic reconnection is accelerated through the formation of multiple magnetic islands as pointed out by the previous studies. Furthermore, we found that

  9. High Reynolds Number Effects on Multi-Hole Probes and Hot Wire Anemometers

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Smith, A.; Gerry, G.; Kauffman, W.

    1995-01-01

    The paper reports on the results from an experimental investigation of the response of multi-hole and hot wire probes at high flow Reynolds numbers (Re approx. 10(exp 6)). The limited results available in literature for 5-hole probes are restricted to Re approx. 10(exp 4). The experiment aims to investigate the probe response (in terms of dimensionless pressure ratios, characterizing pitch, and yaw angles and the total and static pressures) at high Re values and to gauge their effect on the calculated velocity vector. Hot wire calibrations were also undertaken with a parametric variation of the flow pressure, velocity and temperature. Different correction and calibration schemes are sought to be tested against the acquired data set. The data is in the analysis stage at the present time. The test provided good benchmark quality data that can be used to test future calibration and testing methods.

  10. High-Schmidt-number scalar transfer in regular and fractal grid turbulence

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroki; Nagata, Kouji; Sakai, Yasuhiko; Ukai, Ryota

    2010-12-01

    Turbulent mixing of high-Schmidt-number passive scalars in regular and fractal grid turbulence is experimentally investigated using a water channel. A turbulence-generating grid is installed at the entrance of the test section, which is 1.5 m in length and 0.1 m×0.1 m in cross section. Two types of grids are used: one is a regular grid consisting of square-mesh and biplane constructions, and the other is a square-type fractal grid, which was first investigated by Hurst and Vassilicos (2007 Phys. Fluids 19 035103) and Seoud and Vassilicos (2007 Phys. Fluids 19 105108). The two grids have the same solidity of 0.36. The Reynolds number based on the mesh size, ReM=U0Meff/ν, is 2500 in both flows, where U0 is the cross-sectionally averaged mean velocity, Meff is the effective mesh size and ν is the kinematic viscosity. A fluorescent dye (rhodamine B) is homogeneously premixed only in the lower stream and therefore the scalar mixing layers with an initial step profile develop downstream of the grids. The Schmidt number of the dye is O(103). The time-resolved particle image velocimetry and the planar laser-induced fluorescence techniques are used to measure the velocity and concentration fields. The results show that the turbulent mixing in fractal grid turbulence is more strongly enhanced than that in regular grid turbulence for the same mesh Reynolds number ReM. The profile of instantaneous scalar dissipation shows that scalar dissipation takes place locally even in the far downstream region at x/Meff=120 in fractal grid turbulence.

  11. GPU implementation for three-dimensional mantle convection at high Rayleigh number

    NASA Astrophysics Data System (ADS)

    Barnett, G. A.; Wright, G. B.; Yuen, D. A.

    2009-12-01

    The last decade has seen the strong influence exerted by the gaming industry on high-performance scientific computing since the landmark year of 2003 when the speed of floating point operations for GPUs surpassed that of CPUs. Since then, the progress of GPUs has been astounding because of the development of faster components with many flow processing units (cores) and larger memories (240 cores and 4 Gbytes with the NVIDIA Tesla 1060). It is feasible with GPUs to have the potential computing power of around one Teraflop in your office environment for around $5000. In this study we demonstrate the enormous capabilities GPUs offers for certain geophysical fluid dynamics applications. We focus our attention on high Rayleigh number three dimensional mantle convection (ie. Rayleigh-Bénard convection in the infinite Prandtl number limit) in a rectangular box. The model equations are taken from Larsen et al (1997), where a constant viscosity has been assumed, which allows the momentum equations to be decomposed into two coupled Poisson equations involving a scalar potential for computing the velocity. These equations together with the spatial derivatives in the energy equation are approximated with second order finite differences. The whole system is advanced forward in time with an explicit, third order accurate Runge-Kutta scheme, which allows for variable time-stepping. We discuss the method with specific attention given to the solution of the two Poisson equations, which are solved directly with a Fourier transform-based algorithm, eg. Hockney (1965). We compare the implementations of this algorithm and its variations on the GPU vs the CPU and demonstrate how the choice depends on the architecture. We report the results from 3D mantle convection simulations run on a single GPU with Rayleigh number up to 10**7 and grids of size up to 512X512X256 (see figure below). A comparison of the computational time for the GPU code shows a speed up of more than 10 times over the

  12. PET/CT imaging artifacts.

    PubMed

    Sureshbabu, Waheeda; Mawlawi, Osama

    2005-09-01

    The purpose of this paper is to introduce the principles of PET/CT imaging and describe the artifacts associated with it. PET/CT is a new imaging modality that integrates functional (PET) and structural (CT) information into a single scanning session, allowing excellent fusion of the PET and CT images and thus improving lesion localization and interpretation accuracy. Moreover, the CT data can also be used for attenuation correction, ultimately leading to high patient throughput. These combined advantages have rendered PET/CT a preferred imaging modality over dedicated PET. Although PET/CT imaging offers many advantages, this dual-modality imaging also poses some challenges. CT-based attenuation correction can induce artifacts and quantitative errors that can affect the PET emission images. For instance, the use of contrast medium and the presence of metallic implants can be associated with focal radiotracer uptake. Furthermore, the patient's breathing can introduce mismatches between the CT attenuation map and the PET emission data, and the discrepancy between the CT and PET fields of view can lead to truncation artifacts. After reading this article, the technologist should be able to describe the principles of PET/CT imaging, identify at least 3 types of image artifacts, and describe the differences between PET/CT artifacts of different causes: metallic implants, respiratory motion, contrast medium, and truncation. PMID:16145223

  13. HDRMC, an accelerated Monte Carlo dose calculator for high dose rate brachytherapy with CT-compatible applicators

    SciTech Connect

    Chibani, Omar C-M Ma, Charlie

    2014-05-15

    Purpose: To present a new accelerated Monte Carlo code for CT-based dose calculations in high dose rate (HDR) brachytherapy. The new code (HDRMC) accounts for both tissue and nontissue heterogeneities (applicator and contrast medium). Methods: HDRMC uses a fast ray-tracing technique and detailed physics algorithms to transport photons through a 3D mesh of voxels representing the patient anatomy with applicator and contrast medium included. A precalculated phase space file for the{sup 192}Ir source is used as source term. HDRM is calibrated to calculated absolute dose for real plans. A postprocessing technique is used to include the exact density and composition of nontissue heterogeneities in the 3D phantom. Dwell positions and angular orientations of the source are reconstructed using data from the treatment planning system (TPS). Structure contours are also imported from the TPS to recalculate dose-volume histograms. Results: HDRMC was first benchmarked against the MCNP5 code for a single source in homogenous water and for a loaded gynecologic applicator in water. The accuracy of the voxel-based applicator model used in HDRMC was also verified by comparing 3D dose distributions and dose-volume parameters obtained using 1-mm{sup 3} versus 2-mm{sup 3} phantom resolutions. HDRMC can calculate the 3D dose distribution for a typical HDR cervix case with 2-mm resolution in 5 min on a single CPU. Examples of heterogeneity effects for two clinical cases (cervix and esophagus) were demonstrated using HDRMC. The neglect of tissue heterogeneity for the esophageal case leads to the overestimate of CTV D90, CTV D100, and spinal cord maximum dose by 3.2%, 3.9%, and 3.6%, respectively. Conclusions: A fast Monte Carlo code for CT-based dose calculations which does not require a prebuilt applicator model is developed for those HDR brachytherapy treatments that use CT-compatible applicators. Tissue and nontissue heterogeneities should be taken into account in modern HDR

  14. Cone Beam CT-Based Three-Dimensional Planning in High-Dose-Rate Brachytherapy for Cervical Cancer

    SciTech Connect

    Al-Halabi, Hani; Portelance, Lorraine; Duclos, Marie; Reniers, Brigitte; Bahoric, Boris; Souhami, Luis

    2010-07-15

    Purpose: To evaluate dose-volume histograms (DVHs) of bladder and rectum from the use of cone beam CT (CBCT)-based three-dimensional (3D) treatment planning in intracavitary high-dose-rate brachytherapy (HDRB) for cervical cancer patients and to compare these parameters with International Commission on Radiation Units and Measurements (ICRU) of rectal and bladder reference point dose measurements. Methods and Materials: Thirteen patients with cervical cancer underwent HDRB insertions. CT-compatible tandem and ovoid applicators were used to obtain intraoperative CBCT images. The use of a rectal tube and injection of bladder contrast before scanning facilitated contouring the rectum and bladder. All patients underwent intraoperative orthogonal x-ray filming, and treatments were prescribed using standard two-dimensional planning and dosimetry. DVHs for the bladder and rectum were constructed for each treatment. The minimum dose in the most irradiated 2.0-cm{sup 3} volume of bladder (B{sub D2V}) and rectum (R{sub D2V}) were determined from DVHs and compared to ICRU reference point estimates of bladder (B{sub ICRU}) and rectum (R{sub ICRU}) doses. Results: Twenty-six CBCT-based plans were evaluated. The median B{sub ICRU} dose (347 cGy; range, 164-601 cGy) was significantly lower (p < 0.001) than the median B{sub D2V} (594 cGy; range, 260-969 cGy). The median R{sub ICRU} dose (405 cGy; range, 189-700 cGy) was also significantly lower (p = 0.037) than the median R{sub D2V} (488 cGy; range, 227-786 cGy). Conclusions: CBCT-based 3D planning can be used in HDRB for cervical cancer and is a convenient alternative to CT-based planning, with the advantage of minimizing applicator motion. Correlation with late effects will further define the role of CBCT-based 3D dosimetry in HDRB planning.

  15. High-performance computer aided detection system for polyp detection in CT colonography with fluid and fecal tagging

    NASA Astrophysics Data System (ADS)

    Liu, Jiamin; Wang, Shijun; Kabadi, Suraj; Summers, Ronald M.

    2009-02-01

    CT colonography (CTC) is a feasible and minimally invasive method for the detection of colorectal polyps and cancer screening. Computer-aided detection (CAD) of polyps has improved consistency and sensitivity of virtual colonoscopy interpretation and reduced interpretation burden. A CAD system typically consists of four stages: (1) image preprocessing including colon segmentation; (2) initial detection generation; (3) feature selection; and (4) detection classification. In our experience, three existing problems limit the performance of our current CAD system. First, highdensity orally administered contrast agents in fecal-tagging CTC have scatter effects on neighboring tissues. The scattering manifests itself as an artificial elevation in the observed CT attenuation values of the neighboring tissues. This pseudo-enhancement phenomenon presents a problem for the application of computer-aided polyp detection, especially when polyps are submerged in the contrast agents. Second, general kernel approach for surface curvature computation in the second stage of our CAD system could yield erroneous results for thin structures such as small (6-9 mm) polyps and for touching structures such as polyps that lie on haustral folds. Those erroneous curvatures will reduce the sensitivity of polyp detection. The third problem is that more than 150 features are selected from each polyp candidate in the third stage of our CAD system. These high dimensional features make it difficult to learn a good decision boundary for detection classification and reduce the accuracy of predictions. Therefore, an improved CAD system for polyp detection in CTC data is proposed by introducing three new techniques. First, a scale-based scatter correction algorithm is applied to reduce pseudo-enhancement effects in the image pre-processing stage. Second, a cubic spline interpolation method is utilized to accurately estimate curvatures for initial detection generation. Third, a new dimensionality

  16. Flying and swimming animals cruise at a Strouhal number tuned for high power efficiency

    NASA Astrophysics Data System (ADS)

    Taylor, Graham K.; Nudds, Robert L.; Thomas, Adrian L. R.

    2003-10-01

    Dimensionless numbers are important in biomechanics because their constancy can imply dynamic similarity between systems, despite possible differences in medium or scale. A dimensionless parameter that describes the tail or wing kinematics of swimming and flying animals is the Strouhal number, St = fA/U, which divides stroke frequency (f) and amplitude (A) by forward speed (U). St is known to govern a well-defined series of vortex growth and shedding regimes for airfoils undergoing pitching and heaving motions. Propulsive efficiency is high over a narrow range of St and usually peaks within the interval 0.2 < St < 0.4 (refs 3-8). Because natural selection is likely to tune animals for high propulsive efficiency, we expect it to constrain the range of St that animals use. This seems to be true for dolphins, sharks and bony fish, which swim at 0.2 < St < 0.4. Here we show that birds, bats and insects also converge on the same narrow range of St, but only when cruising. Tuning cruise kinematics to optimize St therefore seems to be a general principle of oscillatory lift-based propulsion.

  17. A Monolithic Algorithm for High Reynolds Number Fluid-Structure Interaction Simulations

    NASA Astrophysics Data System (ADS)

    Lieberknecht, Erika; Sheldon, Jason; Pitt, Jonathan

    2013-11-01

    Simulations of fluid-structure interaction problems with high Reynolds number flows are typically approached with partitioned algorithms that leverage the robustness of traditional finite volume method based CFD techniques for flows of this nature. However, such partitioned algorithms are subject to many sub-iterations per simulation time-step, which substantially increases the computational cost when a tightly coupled solution is desired. To address this issue, we present a finite element method based monolithic algorithm for fluid-structure interaction problems with high Reynolds number flow. The use of a monolithic algorithm will potentially reduce the computational cost during each time-step, but requires that all of the governing equations be simultaneously cast in a single Arbitrary Lagrangian-Eulerian (ALE) frame of reference and subjected to the same discretization strategy. The formulation for the fluid solution is stabilized by implementing a Streamline Upwind Galerkin (SUPG) method, and a projection method for equal order interpolation of all of the solution unknowns; numerical and programming details are discussed. Preliminary convergence studies and numerical investigations are presented, to demonstrate the algorithm's robustness and performance. The authors acknowledge support for this project from the Applied Research Laboratory Eric Walker Graduate Fellowship Program.

  18. An Experimental Simulation of Flap Flow on Multielement Airfoils at High Reynolds Number

    NASA Technical Reports Server (NTRS)

    Schneider, S.; Campbell, B.; Bucci, G.; Sullivan, J.

    1994-01-01

    The design of the high lift system has a major impact on the performance of an aircraft yet our understanding of the physics of this flow is still weak. Flow features include interactions between the wakes shed from the upstream elements and the pressure gradients and boundary layers of the downstream elements. Interaction of the turbulent wake of the main element and the flap can cause (1) separation of the flap boundary layer or (2) 'bursting' of the main airfoil wake. Although the first factor is at least partially understood, even the qualitative aspects of (2) remain to be determined. In order to study these phenomena at Reynolds numbers approaching those of flight, a thick high Reynolds number wake is created using a 24 foot flat plate in the long rectangular test section of a 4 ft. by 6 ft subsonic wind tunnel. The design and construction of this test section, plate, and accompanying flap is described. Results obtained in a quarter-scale model were used for design purposes and are also described. Construction of the full scale facility is complete and preliminary results are presented.

  19. Flying and swimming animals cruise at a Strouhal number tuned for high power efficiency.

    PubMed

    Taylor, Graham K; Nudds, Robert L; Thomas, Adrian L R

    2003-10-16

    Dimensionless numbers are important in biomechanics because their constancy can imply dynamic similarity between systems, despite possible differences in medium or scale. A dimensionless parameter that describes the tail or wing kinematics of swimming and flying animals is the Strouhal number, St = fA/U, which divides stroke frequency (f) and amplitude (A) by forward speed (U). St is known to govern a well-defined series of vortex growth and shedding regimes for airfoils undergoing pitching and heaving motions. Propulsive efficiency is high over a narrow range of St and usually peaks within the interval 0.2 < St < 0.4 (refs 3-8). Because natural selection is likely to tune animals for high propulsive efficiency, we expect it to constrain the range of St that animals use. This seems to be true for dolphins, sharks and bony fish, which swim at 0.2 < St < 0.4. Here we show that birds, bats and insects also converge on the same narrow range of St, but only when cruising. Tuning cruise kinematics to optimize St therefore seems to be a general principle of oscillatory lift-based propulsion. PMID:14562101

  20. A high-resolution imaging technique using a whole-body, research photon counting detector CT system

    NASA Astrophysics Data System (ADS)

    Leng, S.; Yu, Z.; Halaweish, A.; Kappler, S.; Hahn, K.; Henning, A.; Li, Z.; Lane, J.; Levin, D. L.; Jorgensen, S.; Ritman, E.; McCollough, C.

    2016-03-01

    A high-resolution (HR) data collection mode has been introduced to a whole-body, research photon-counting-detector CT system installed in our laboratory. In this mode, 64 rows of 0.45 mm x 0.45 mm detector pixels were used, which corresponded to a pixel size of 0.25 mm x 0.25 mm at the iso-center. Spatial resolution of this HR mode was quantified by measuring the MTF from a scan of a 50 micron wire phantom. An anthropomorphic lung phantom, cadaveric swine lung, temporal bone and heart specimens were scanned using the HR mode, and image quality was subjectively assessed by two experienced radiologists. High spatial resolution of the HR mode was evidenced by the MTF measurement, with 15 lp/cm and 20 lp/cm at 10% and 2% modulation. Images from anthropomorphic phantom and cadaveric specimens showed clear delineation of small structures, such as lung vessels, lung nodules, temporal bone structures, and coronary arteries. Temporal bone images showed critical anatomy (i.e. stapes superstructure) that was clearly visible in the PCD system. These results demonstrated the potential application of this imaging mode in lung, temporal bone, and vascular imaging. Other clinical applications that require high spatial resolution, such as musculoskeletal imaging, may also benefit from this high resolution mode.

  1. A High-Resolution Imaging Technique using a Whole-body, Research Photon Counting Detector CT System

    PubMed Central

    Leng, S.; Yu, Z.; Halaweish, A.; Kappler, S.; Hahn, K.; Henning, A.; Li, Z.; Lane, J.; Levin, D. L.; Jorgensen, S.; Ritman, E.; McCollough, C.

    2016-01-01

    A high-resolution (HR) data collection mode has been introduced to the whole-body, research photon-counting-detector CT system installed in our laboratory. In this mode, 64 rows of 0.45 mm × 0.45 mm detectors pixels were used, which corresponded to a pixel size of 0.225 mm × 0.225 mm at the iso-center. Spatial resolution of this HR mode was quantified by measuring the MTF from a scan of a 50 micron wire phantom. An anthropomorphic lung phantom, cadaveric swine lung, temporal bone and heart specimens were scanned using the HR mode, and image quality was subjectively assessed by two experienced radiologists. Comparison of the HR mode images against their energy integrating system (EID) equivalents using comb filters was also performed. High spatial resolution of the HR mode was evidenced by the MTF measurement, with 15 lp/cm and 20 lp/cm at 10% and 2% MTF. Images from anthropomorphic phantom and cadaveric specimens showed clear delineation of small structures, such as lung vessels, lung nodules, temporal bone structures, and coronary arteries. Temporal bone images showed critical anatomy (i.e. stapes superstructure) that was clearly visible in the PCD system but hardly visible with the EID system. These results demonstrated the potential application of this imaging mode in lung, temporal bone, and vascular imaging. Other clinical applications that require high spatial resolution, such as musculoskeletal imaging, may also benefit from this high resolution mode. PMID:27330238

  2. Time-averaged flow over a hydrofoil at high Reynolds number

    NASA Astrophysics Data System (ADS)

    Bourgoyne, Dwayne A.; Hamel, Joshua M.; Ceccio, Steven L.; Dowling, David R.

    2003-12-01

    At high Reynolds number, the flow of an incompressible viscous fluid over a lifting surface is a rich blend of fluid dynamic phenomena. Here, boundary layers formed at the leading edge develop over both the suction and pressure sides of the lifting surface, transition to turbulence, separate near the foil's trailing edge, combine in the near wake, and eventually form a turbulent far-field wake. The individual elements of this process have been the subject of much prior work. However, controlled experimental investigations of these flow phenomena and their interaction on a lifting surface at Reynolds numbers typical of heavy-lift aircraft wings or full-size ship propellers (chord-based Reynolds numbers, Re_C {˜} 10(7{-}10^8) ) are largely unavilable. This paper presents results from an experimental effort to identify and measure the dominant features of the flow over a two-dimensional hydrofoil at nominal Re_C values from near one million to more than 50 million. The experiments were conducted in the US Navy's William B. Morgan Large Cavitation Channel with a solid-bronze hydrofoil (2.1 m chord, 3.0 m span, 17 cm maximum thickness) at flow speeds from 0.25 to 18.3 m s(-1) . The foil section, a modified NACA 16 with a pressure side that is nearly flat and a suction side that terminates in a blunt trailing-edge bevel, approximates the cross-section of a generic naval propeller blade. Time-averaged flow-field measurements drawn from laser-Doppler velocimetry, particle-imaging velocimetry, and static pressure taps were made for two trailing-edge bevel angles (44 (°) and 56 (°) ). These velocity and pressure measurements were concentrated in the trailing-edge and near-wake regions, but also include flow conditions upstream and far downstream of the foil, as well as static pressure distributions on the foil surface and test section walls. Observed Reynolds-number variations in the time-averaged flow over the foil are traced to changes in suction-side boundary

  3. Medipix-based Spectral Micro-CT

    PubMed Central

    Xu, Qiong; He, Peng; Bennett, James; Amir, Raja; Dobbs, Bruce; Mou, Xuanqin; Wei, Biao; Butler, Anthony; Butler, Phillip; Wang, Ge

    2013-01-01

    Since Hounsfield's Nobel Prize winning breakthrough decades ago, X-ray CT has been widely applied in the clinical and preclinical applications - producing a huge number of tomographic gray-scale images. However, these images are often insufficient to distinguish crucial differences needed for diagnosis. They have poor soft tissue contrast due to inherent photon-count issues, involving high radiation dose. By physics, the X-ray spectrum is polychromatic, and it is now feasible to obtain multi-energy, spectral, or true-color, CT images. Such spectral images promise powerful new diagnostic information. The emerging Medipix technology promises energy-sensitive, high-resolution, accurate and rapid X-ray detection. In this paper, we will review the recent progress of Medipix-based spectral micro-CT with the emphasis on the results obtained by our team. It includes the state- of-the-art Medipix detector, the system and method of a commercial MARS (Medipix All Resolution System) spectral micro-CT, and the design and color diffusion of a hybrid spectral micro-CT. PMID:24194631

  4. Medipix-based Spectral Micro-CT.

    PubMed

    Yu, Hengyong; Xu, Qiong; He, Peng; Bennett, James; Amir, Raja; Dobbs, Bruce; Mou, Xuanqin; Wei, Biao; Butler, Anthony; Butler, Phillip; Wang, Ge

    2012-12-01

    Since Hounsfield's Nobel Prize winning breakthrough decades ago, X-ray CT has been widely applied in the clinical and preclinical applications - producing a huge number of tomographic gray-scale images. However, these images are often insufficient to distinguish crucial differences needed for diagnosis. They have poor soft tissue contrast due to inherent photon-count issues, involving high radiation dose. By physics, the X-ray spectrum is polychromatic, and it is now feasible to obtain multi-energy, spectral, or true-color, CT images. Such spectral images promise powerful new diagnostic information. The emerging Medipix technology promises energy-sensitive, high-resolution, accurate and rapid X-ray detection. In this paper, we will review the recent progress of Medipix-based spectral micro-CT with the emphasis on the results obtained by our team. It includes the state- of-the-art Medipix detector, the system and method of a commercial MARS (Medipix All Resolution System) spectral micro-CT, and the design and color diffusion of a hybrid spectral micro-CT. PMID:24194631

  5. Clinical application of in vivo treatment delivery verification based on PET/CT imaging of positron activity induced at high energy photon therapy

    NASA Astrophysics Data System (ADS)

    Janek Strååt, Sara; Andreassen, Björn; Jonsson, Cathrine; Noz, Marilyn E.; Maguire, Gerald Q., Jr.; Näfstadius, Peder; Näslund, Ingemar; Schoenahl, Frederic; Brahme, Anders

    2013-08-01

    The purpose of this study was to investigate in vivo verification of radiation treatment with high energy photon beams using PET/CT to image the induced positron activity. The measurements of the positron activation induced in a preoperative rectal cancer patient and a prostate cancer patient following 50 MV photon treatments are presented. A total dose of 5 and 8 Gy, respectively, were delivered to the tumors. Imaging was performed with a 64-slice PET/CT scanner for 30 min, starting 7 min after the end of the treatment. The CT volume from the PET/CT and the treatment planning CT were coregistered by matching anatomical reference points in the patient. The treatment delivery was imaged in vivo based on the distribution of the induced positron emitters produced by photonuclear reactions in tissue mapped on to the associated dose distribution of the treatment plan. The results showed that spatial distribution of induced activity in both patients agreed well with the delivered beam portals of the treatment plans in the entrance subcutaneous fat regions but less so in blood and oxygen rich soft tissues. For the preoperative rectal cancer patient however, a 2 ± (0.5) cm misalignment was observed in the cranial-caudal direction of the patient between the induced activity distribution and treatment plan, indicating a beam patient setup error. No misalignment of this kind was seen in the prostate cancer patient. However, due to a fast patient setup error in the PET/CT scanner a slight mis-position of the patient in the PET/CT was observed in all three planes, resulting in a deformed activity distribution compared to the treatment plan. The present study indicates that the induced positron emitters by high energy photon beams can be measured quite accurately using PET imaging of subcutaneous fat to allow portal verification of the delivered treatment beams. Measurement of the induced activity in the patient 7 min after receiving 5 Gy involved count rates which were about

  6. Clinical application of in vivo treatment delivery verification based on PET/CT imaging of positron activity induced at high energy photon therapy.

    PubMed

    Janek Strååt, Sara; Andreassen, Björn; Jonsson, Cathrine; Noz, Marilyn E; Maguire, Gerald Q; Näfstadius, Peder; Näslund, Ingemar; Schoenahl, Frederic; Brahme, Anders

    2013-08-21

    The purpose of this study was to investigate in vivo verification of radiation treatment with high energy photon beams using PET/CT to image the induced positron activity. The measurements of the positron activation induced in a preoperative rectal cancer patient and a prostate cancer patient following 50 MV photon treatments are presented. A total dose of 5 and 8 Gy, respectively, were delivered to the tumors. Imaging was performed with a 64-slice PET/CT scanner for 30 min, starting 7 min after the end of the treatment. The CT volume from the PET/CT and the treatment planning CT were coregistered by matching anatomical reference points in the patient. The treatment delivery was imaged in vivo based on the distribution of the induced positron emitters produced by photonuclear reactions in tissue mapped on to the associated dose distribution of the treatment plan. The results showed that spatial distribution of induced activity in both patients agreed well with the delivered beam portals of the treatment plans in the entrance subcutaneous fat regions but less so in blood and oxygen rich soft tissues. For the preoperative rectal cancer patient however, a 2 ± (0.5) cm misalignment was observed in the cranial-caudal direction of the patient between the induced activity distribution and treatment plan, indicating a beam patient setup error. No misalignment of this kind was seen in the prostate cancer patient. However, due to a fast patient setup error in the PET/CT scanner a slight mis-position of the patient in the PET/CT was observed in all three planes, resulting in a deformed activity distribution compared to the treatment plan. The present study indicates that the induced positron emitters by high energy photon beams can be measured quite accurately using PET imaging of subcutaneous fat to allow portal verification of the delivered treatment beams. Measurement of the induced activity in the patient 7 min after receiving 5 Gy involved count rates which were about

  7. High night temperatures during grain number determination reduce wheat and barley grain yield: a field study.

    PubMed

    García, Guillermo A; Dreccer, M Fernanda; Miralles, Daniel J; Serrago, Román A

    2015-11-01

    Warm nights are a widespread predicted feature of climate change. This study investigated the impact of high night temperatures during the critical period for grain yield determination in wheat and barley crops under field conditions, assessing the effects on development, growth and partitioning crop-level processes driving grain number per unit area (GN). Experiments combined: (i) two contrasting radiation and temperature environments: late sowing in 2011 and early sowing in 2013, (ii) two well-adapted crops with similar phenology: bread wheat and two-row malting barley and (iii) two temperature regimes: ambient and high night temperatures. The night temperature increase (ca. 3.9 °C in both crops and growing seasons) was achieved using purpose-built heating chambers placed on the crop at 19:000 hours and removed at 7:00 hours every day from the third detectable stem node to 10 days post-flowering. Across growing seasons and crops, the average minimum temperature during the critical period ranged from 11.2 to 17.2 °C. Wheat and barley grain yield were similarly reduced under warm nights (ca. 7% °C(-1) ), due to GN reductions (ca. 6% °C(-1) ) linked to a lower number of spikes per m(2) . An accelerated development under high night temperatures led to a shorter critical period duration, reducing solar radiation capture with negative consequences for biomass production, GN and therefore, grain yield. The information generated could be used as a starting point to design management and/or breeding strategies to improve crop adaptation facing climate change. PMID:26111197

  8. Application of Gaseous Laser Targets and Optical Diagnostics to Study High Mach Number Unstable Plasma Flows

    SciTech Connect

    Edwards, J; MacKinnon, A; Robey, H

    2001-04-01

    The information that can be obtained from current laser driven high Mach number (compressible) hydrodynamics experiments using solid targets and foams is limited by the need to use X-ray diagnostics. These do well at providing the shape of gross 2D structures which we model well, but are a long way from being able to reveal detailed information at the smaller spatial scales, or in 3D turbulent flows, where most of the modeling uncertainties exist. Remedying this is, and will continue to be, an ongoing research effort. An alternative approach that is not being considered is to use gaseous targets coupled with optical diagnostics. The lower density of gases compared to solids or foams means we can use much larger targets for a given laser energy. This should significantly improve spatial resolution, and the dynamic range of scales that are resolvable. In addition, it may be possible to adapt powerful techniques, such as LIF, used by the low Mach number (incompressible) fluid/gas community so that they work in the high Mach number plasma regime. This would provide much more detailed information on turbulent flows than could be achieved with current X-ray diagnostics. We propose a small research effort to use established techniques such as optical interferometry (absolute electron density), and Schlieren photography (electron density gradient), to study compressible hydrodynamic instabilities. We also propose to explore whether techniques such as LIF may be adapted to the plasma regime, thus providing detailed information, particularly about turbulent flows, that is not currently obtainable in plasmas using X-ray diagnostics. The setting will be radiating blast waves, which avoids costly target fabrication, while promising a high physics payoff to the astrophysics community just from using the established diagnostics alone. We propose to conduct the work in collaboration with Dr Todd Ditmire at the University of Texas at Austin, principally on the Janus laser, and

  9. Investigating the limits of PET/CT imaging at very low true count rates and high random fractions in ion-beam therapy monitoring

    SciTech Connect

    Kurz, Christopher Bauer, Julia; Conti, Maurizio; Guérin, Laura; Eriksson, Lars; Parodi, Katia

    2015-07-15

    Purpose: External beam radiotherapy with protons and heavier ions enables a tighter conformation of the applied dose to arbitrarily shaped tumor volumes with respect to photons, but is more sensitive to uncertainties in the radiotherapeutic treatment chain. Consequently, an independent verification of the applied treatment is highly desirable. For this purpose, the irradiation-induced β{sup +}-emitter distribution within the patient is detected shortly after irradiation by a commercial full-ring positron emission tomography/x-ray computed tomography (PET/CT) scanner installed next to the treatment rooms at the Heidelberg Ion-Beam Therapy Center (HIT). A major challenge to this approach is posed by the small number of detected coincidences. This contribution aims at characterizing the performance of the used PET/CT device and identifying the best-performing reconstruction algorithm under the particular statistical conditions of PET-based treatment monitoring. Moreover, this study addresses the impact of radiation background from the intrinsically radioactive lutetium-oxyorthosilicate (LSO)-based detectors at low counts. Methods: The authors have acquired 30 subsequent PET scans of a cylindrical phantom emulating a patientlike activity pattern and spanning the entire patient counting regime in terms of true coincidences and random fractions (RFs). Accuracy and precision of activity quantification, image noise, and geometrical fidelity of the scanner have been investigated for various reconstruction algorithms and settings in order to identify a practical, well-suited reconstruction scheme for PET-based treatment verification. Truncated listmode data have been utilized for separating the effects of small true count numbers and high RFs on the reconstructed images. A corresponding simulation study enabled extending the results to an even wider range of counting statistics and to additionally investigate the impact of scatter coincidences. Eventually, the recommended

  10. An improved high order texture features extraction method with application to pathological diagnosis of colon lesions for CT colonography

    NASA Astrophysics Data System (ADS)

    Song, Bowen; Zhang, Guopeng; Lu, Hongbing; Wang, Huafeng; Han, Fangfang; Zhu, Wei; Liang, Zhengrong

    2014-03-01

    Differentiation of colon lesions according to underlying pathology, e.g., neoplastic and non-neoplastic, is of fundamental importance for patient management. Image intensity based textural features have been recognized as a useful biomarker for the differentiation task. In this paper, we introduce high order texture features, beyond the intensity, such as gradient and curvature, for that task. Based on the Haralick texture analysis method, we introduce a virtual pathological method to explore the utility of texture features from high order differentiations, i.e., gradient and curvature, of the image intensity distribution. The texture features were validated on database consisting of 148 colon lesions, of which 35 are non-neoplastic lesions, using the random forest classifier and the merit of area under the curve (AUC) of the receiver operating characteristics. The results show that after applying the high order features, the AUC was improved from 0.8069 to 0.8544 in differentiating non-neoplastic lesion from neoplastic ones, e.g., hyperplastic polyps from tubular adenomas, tubulovillous adenomas and adenocarcinomas. The experimental results demonstrated that texture features from the higher order images can significantly improve the classification accuracy in pathological differentiation of colorectal lesions. The gain in differentiation capability shall increase the potential of computed tomography (CT) colonography for colorectal cancer screening by not only detecting polyps but also classifying them from optimal polyp management for the best outcome in personalized medicine.

  11. Metabarcoding analysis of home composts reveals distinctive fungal communities with a high number of unassigned sequences.

    PubMed

    Langarica-Fuentes, Adrian; Fox, Graeme; Robson, Geoffrey D

    2015-10-01

    Home composting has been strongly advocated in the UK, Europe and North America to divert organic waste away from conventional waste processing. Despite this, little attention has been given to microbial communities and their diversity in these systems. In this study, we examined the diversity of fungal species in 10 different domestic composts by 454 tag-encoded pyrosequencing. We report the recovery of 478 different molecular operational taxonomic units (MOTUs) from the 10 composts with a mean of 176.7 ± 19.6 MOTUs per compost and a mean of 12.9 ± 3.8 unique MOTUs per sample. Microascales (17.21 %), Hypocreales (16.76 %), Sordariales (14.89 %), Eurotiales (11.25 %) and Mortierellales (7.38 %) were the dominant orders in the community, with Pseudallescheria (9.52 %), Penicillium (8.43 %), Mortierella (3.60 %) and Fusarium (3.31 %) being the most abundant genera. Fungal communities in home composts were substantially different to large-scale commercial composts, with thermophilic and thermotolerant fungi present in much lower numbers. Significantly, 46.2 % of all sequences were identified as uncultured fungi or could not be assigned above the family level, suggesting there are a high number of new genera and species in these environments still to be described. PMID:26243286

  12. Optimizing sparse sequencing of single cells for highly multiplex copy number profiling

    PubMed Central

    Baslan, Timour; Kendall, Jude; Ward, Brian; Cox, Hilary; Leotta, Anthony; Rodgers, Linda; Riggs, Michael; D'Italia, Sean; Sun, Guoli; Yong, Mao; Miskimen, Kristy; Gilmore, Hannah; Saborowski, Michael; Dimitrova, Nevenka; Krasnitz, Alexander; Harris, Lyndsay; Wigler, Michael; Hicks, James

    2015-01-01

    Genome-wide analysis at the level of single cells has recently emerged as a powerful tool to dissect genome heterogeneity in cancer, neurobiology, and development. To be truly transformative, single-cell approaches must affordably accommodate large numbers of single cells. This is feasible in the case of copy number variation (CNV), because CNV determination requires only sparse sequence coverage. We have used a combination of bioinformatic and molecular approaches to optimize single-cell DNA amplification and library preparation for highly multiplexed sequencing, yielding a method that can produce genome-wide CNV profiles of up to a hundred individual cells on a single lane of an Illumina HiSeq instrument. We apply the method to human cancer cell lines and biopsied cancer tissue, thereby illustrating its efficiency, reproducibility, and power to reveal underlying genetic heterogeneity and clonal phylogeny. The capacity of the method to facilitate the rapid profiling of hundreds to thousands of single-cell genomes represents a key step in making single-cell profiling an easily accessible tool for studying cell lineage. PMID:25858951

  13. Neutrino properties deduced from the study of lepton number violating processes at low and high energies

    SciTech Connect

    Stoica, Sabin

    2012-11-20

    There is nowadays a significant progress in understanding the neutrino properties. The results of the neutrino oscillation experiments have convincingly showed that neutrinos have mass and oscillate, in contradiction with the Standard Model (SM) assumptions, and these are the first evidences of beyond SM physics. However, fundamental properties of the neutrinos like their absolute mass, their character (are they Dirac or Majorana particles?), their mass hierarchy, the number of neutrino flavors, etc., still remain unknown. In this context there is an increased interest in the study of the lepton number violating (LNV) processes, since they could complete our understanding on the neutrino properties. Since recently, the neutrinoless double beta decay was considered the only process able to distinguish between Dirac or Majorana neutrinos and to give a hint on the absolute mass of the electron neutrino. At present, the increased luminosity of the LHC experiments makes feasible the search of LNV processes at high energy as well. In this lecture I will make a brief review on our present knowledge of the neutrino properties, on the present status of the double-beta decay studies and on the first attempts to search LNV processes at LHC.

  14. Muons in air showers at the Pierre Auger Observatory: Mean number in highly inclined events

    SciTech Connect

    Aab, Alexander

    2015-03-09

    We present the first hybrid measurement of the average muon number in air showers at ultra-high energies, initiated by cosmic rays with zenith angles between 62° and 80° . Our measurement is based on 174 hybrid events recorded simultaneously with the Surface Detector array and the Fluorescence Detector of the Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. A 1019 eV shower with a zenith angle of 67°, which arrives at the Surface Detector array at an altitude of 1450 m above sea level, contains on average (2.68 ± 0.04 ± 0.48 (sys.)) × 107 muons with energies larger than 0.3 GeV. Finally, the logarithmic gain d ln Nµ/d ln E of muons with increasing energy between 4 × 1018 eV and 5 × 1019 eV is measured to be (1.029 ± 0.024 ± 0.030 (sys.)).

  15. Improvements of a nano-scale crossed hot-wire for high Reynolds number measurements

    NASA Astrophysics Data System (ADS)

    Fan, Yuyang; Hultmark, Marcus

    2015-11-01

    Hot-wire anemometry, despite its limited spatial and temporal resolution, is still the preferred tool for high Reynolds number flow measurements, mainly due to the continuous signal. To address the resolution issues, the Nano-Scale Thermal Anemometry Probe (NSTAP) was developed at Princeton University. The NSTAP has a sensing volume more than one order of magnitude smaller than conventional hot-wires, and it has displayed superior performance. However, the NSTAP can only measure a single component of the velocity. Using a novel combining method, a probe that enables two-component velocity measurements has been created (the x-NSTAP). The measurement volume is approximately 50 × 50 × 50 μ m, more than one order of magnitude smaller in all directions compared to conventional crossed hot-wires. The x-NSTAP has been further improved to allow more accurate measurements with the help of flow visualization using a scaled model but matching Reynolds number. Results from turbulent flow measurements with the new x-NSTAP are also presented. Supported under NSF grant CBET-1510100 (program manager Dimitrios Papavassiliou).

  16. Heat transfer predictions for two turbine nozzle geometries at high Reynolds and Mach numbers

    NASA Technical Reports Server (NTRS)

    Boyle, R. J.; Jackson, R.

    1995-01-01

    Predictions of turbine vane and endwall heat transfer and pressure distributions are compared with experimental measurements for two vane geometries. The differences in geometries were due to differences in the hub profile, and both geometries were derived from the design of a high rim speed turbine (HRST). The experiments were conducted in the Isentropic Light Piston Facility (ILPF) at Pyestock at a Reynolds number of 5.3 x 10(exp 6), a Mach number of 1.2, and a wall-to-gas temperature ratio of 0.66. Predictions are given for two different steady-state three-dimensional Navier-Stokes computational analyses. C-type meshes were used, and algebraic models were employed to calculate the turbulent eddy viscosity. The effects of different turbulence modeling assumptions on the predicted results are examined. Comparisons are also given between predicted and measured total pressure distributions behind the vane. The combination of realistic engine geometries and flow conditions proved to be quite demanding in terms of the convergence of the CFD solutions. An appropriate method of grid generation, which resulted in consistently converged CFD solutions, was identified.

  17. Muons in air showers at the Pierre Auger Observatory: Mean number in highly inclined events

    DOE PAGESBeta

    Aab, Alexander

    2015-03-09

    We present the first hybrid measurement of the average muon number in air showers at ultra-high energies, initiated by cosmic rays with zenith angles between 62° and 80° . Our measurement is based on 174 hybrid events recorded simultaneously with the Surface Detector array and the Fluorescence Detector of the Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. A 1019 eV shower with a zenith angle of 67°, which arrives at the Surface Detector array at anmore » altitude of 1450 m above sea level, contains on average (2.68 ± 0.04 ± 0.48 (sys.)) × 107 muons with energies larger than 0.3 GeV. Finally, the logarithmic gain d ln Nµ/d ln E of muons with increasing energy between 4 × 1018 eV and 5 × 1019 eV is measured to be (1.029 ± 0.024 ± 0.030 (sys.)).« less

  18. High-Order Photonic W-states for Random Number Generation

    NASA Astrophysics Data System (ADS)

    Graefe, Markus; Heilmann, Rene; Perez-Leija, Armando; Keil, Robert; Dreisow, Felix; Heinrich, Matthias; Nolte, Stefan; Christodoulides, Demetrios N.; Szameit, Alexander

    2014-05-01

    Multipartite entanglement plays a key role in a number of counter-intuitive phenomena in quantum me- chances. A particular type of multipartite entangled states are the so called W-states which are in generalized form a coherent superposition of N single qubit states exhibiting equal probability amplitudes. The entanglement carried by these quantum entities has the remarkable property of being intrinsically robust to decoherence in one of the qubits. In our work, we experimentally realize high order W-states by forcing single photons to exist in a uniform coherent superposition of N (up to 16) spatial optical modes within a multi-port integrated system. Interestingly, in the generated W-states, a single photon will emerge from any of the N output ports with exactly the same probability. Based on that fact we have additionally developed a scheme for the generation of genuine random bits on chip, without the need of any post-processig. The authenticity of the random numbers is validated by applying the fifteen statistical tests suggested by National Institute of Standard Technology.

  19. Jet Velocity Profile Effects on Spray Characteristics of Impinging Jets at High Reynolds and Weber Numbers

    NASA Astrophysics Data System (ADS)

    Rodrigues, Neil S.; Kulkarni, Varun; Sojka, Paul E.

    2014-11-01

    While like-on-like doublet impinging jet atomization has been extensively studied in the literature, there is poor agreement between experimentally observed spray characteristics and theoretical predictions (Ryan et al. 1995, Anderson et al. 2006). Recent works (Bremond and Villermaux 2006, Choo and Kang 2007) have introduced a non-uniform jet velocity profile, which lead to a deviation from the standard assumptions for the sheet velocity and the sheet thickness parameter. These works have assumed a parabolic profile to serve as another limit to the traditional uniform jet velocity profile assumption. Incorporating a non-uniform jet velocity profile results in the sheet velocity and the sheet thickness parameter depending on the sheet azimuthal angle. In this work, the 1/7th power-law turbulent velocity profile is assumed to provide a closer match to the flow behavior of jets at high Reynolds and Weber numbers, which correspond to the impact wave regime. Predictions for the maximum wavelength, sheet breakup length, ligament diameter, and drop diameter are compared with experimental observations. The results demonstrate better agreement between experimentally measured values and predictions, compared to previous models. U.S. Army Research Office under the Multi-University Research Initiative Grant Number W911NF-08-1-0171.

  20. Heat transfer predictions for two turbine nozzle geometries at high Reynolds and Mach numbers

    NASA Astrophysics Data System (ADS)

    Boyle, R. J.; Jackson, R.

    1995-09-01

    Predictions of turbine vane and endwall heat transfer and pressure distributions are compared with experimental measurements for two vane geometries. The differences in geometries were due to differences in the hub profile, and both geometries were derived from the design of a high rim speed turbine (HRST). The experiments were conducted in the Isentropic Light Piston Facility (ILPF) at Pyestock at a Reynolds number of 5.3 x 10(exp 6), a Mach number of 1.2, and a wall-to-gas temperature ratio of 0.66. Predictions are given for two different steady-state three-dimensional Navier-Stokes computational analyses. C-type meshes were used, and algebraic models were employed to calculate the turbulent eddy viscosity. The effects of different turbulence modeling assumptions on the predicted results are examined. Comparisons are also given between predicted and measured total pressure distributions behind the vane. The combination of realistic engine geometries and flow conditions proved to be quite demanding in terms of the convergence of the CFD solutions. An appropriate method of grid generation, which resulted in consistently converged CFD solutions, was identified.

  1. A Stochastic Model for the Relative Motion of High Stokes Number Particles in Isotropic Turbulence

    NASA Astrophysics Data System (ADS)

    Dhariwal, Rohit; Rani, Sarma; Koch, Donald

    2014-11-01

    In the current study, a novel analytical closure for the diffusion current in the PDF equation is presented that is applicable to high-inertia particle pairs with Stokes numbers Str >> 1 . Here Str is a Stokes number based on the time-scale τr of eddies whose size scales with pair separation r. Using this closure, Langevin equations were solved to evolve particle-pair relative velocities and separations in stationary isotropic turbulence. The Langevin equation approach enables the simulation of the full PDF of pair relative motion, instead of only the first few moments of the PDF as is the case in a moments-based approach. Accordingly, PDFs Ω (U | r) and Ω (Ur | r) are computed for various separations r, where the former is the PDF of relative velocity U and the latter is the PDF of the radial component of relative velocity Ur, both conditioned upon the separation r. Consistent with the DNS study of Sundaram & Collins, the Langevin simulations capture the transition of Ω (U | r) from being Gaussian at integral-scale separations to an exponential PDF at Kolmogorov-scale separations. The radial distribution functions (RDFs) computed from these simulations also show reasonable quantitative agreement with those from the DNS of Fevrier et al.

  2. Time evolution of atmospheric particle number concentration during high-intensity pyrotechnic events

    NASA Astrophysics Data System (ADS)

    Crespo, Javier; Yubero, Eduardo; Nicolás, Jose F.; Caballero, Sandra; Galindo, Nuria

    2014-10-01

    The Mascletàs are high-intensity pyrotechnic events, typical of eastern Spanish festivals, in which thousands of firecrackers are burnt at ground level in an intense, short-time (<8 min) deafening spectacle that generates short-lived, thick aerosol clouds. In this study, the impact of such events on air quality has been evaluated by means of particle number concentration measurements performed close to the venue during the June festival in Alicante (southeastern Spain). Peak concentrations and dilution times observed throughout the Mascletàs have been compared to those measured when conventional aerial fireworks were launched 2 km away from the monitoring site. The impact of the Mascletàs on the total number concentration of particles larger than 0.3 μm was higher (maximum ˜2·104 cm-3) than that of fireworks (maximum ˜2·103 cm-3). The effect of fireworks depended on whether the dominant meteorological conditions favoured the transport of the plume to the measurement location. However, the time required for particle concentrations to return to background levels is longer and more variable for firework displays (minutes to hours) than for the Mascletàs (<25 min).

  3. Factors Influencing the Occurrence of High Numbers of Iodine-Resistant Bacteria in Iodinated Swimming Pools

    PubMed Central

    Favero, Martin S.; Drake, Charles H.

    1966-01-01

    It has been shown that, although iodinated swimming-pool waters are usually free from coliform bacteria and enterococci, the total counts frequently become relatively high. Pseudomonas alcaligenes and Alcaligenes faecalis have been shown to account for most of these high counts. It was of interest, therefore, to compare the microbial flora of four alternately chlorinated and iodinated swimming pools. By means of the membrane filter method and suitable selective media, examinations were made for total viable counts, coliform bacteria, enterococci, staphylococci, Streptococcus salivarius, and P. aeruginosa. Colonies also were picked from membrane filters incubated on standard plate count agar and identified. The results showed that, although viable counts were significantly higher during the iodinated periods, the specific types of bacteria determined were either fewer than or the same as in chlorinated periods. During chlorination, the predominant microbial flora consisted of staphylococci and members of the genus Bacillus. During iodination, however, the P. alcaligenes-A. faecalis group accounted for 92 to 99% of the microbial flora. The accumulation of high numbers of these bacteria was shown to be due to their iodine resistance and their ability to grow rapidly in pool water in the absence of free iodine. PMID:5927040

  4. Electron acceleration in a nonrelativistic shock with very high Alfvén Mach number.

    PubMed

    Matsumoto, Y; Amano, T; Hoshino, M

    2013-11-22

    Electron acceleration associated with various plasma kinetic instabilities in a nonrelativistic shock with very high Alfvén Mach number (M(A)~45) is revealed by means of a two-dimensional fully kinetic particle-in-cell simulation. Electromagnetic (ion Weibel) and electrostatic (ion-acoustic and Buneman) instabilities are strongly activated at the same time in different regions of the two-dimensional shock structure. Relativistic electrons are quickly produced predominantly by the shock surfing mechanism with the Buneman instability at the leading edge of the foot. The energy spectrum has a high-energy tail exceeding the upstream ion kinetic energy accompanying the main thermal population. This gives a favorable condition for the ion-acoustic instability at the shock front, which in turn results in additional energization. The large-amplitude ion Weibel instability generates current sheets in the foot, implying another dissipation mechanism via magnetic reconnection in a three-dimensional shock structure in the very-high-M(A) regime. PMID:24313495

  5. Diffusion velocity correlation for nuclear graphite gasification at high temperature and low Reynolds numbers

    SciTech Connect

    El-Genk, M. S.; Tournier, J. M. P.

    2012-07-01

    The safety analysis of High-Temperature and Very High Temperature gas-cooled Reactors requires reliable estimates of nuclear graphite gasification as a function of temperature, among other parameters, in the unlikely event of an air ingress accident. Although the rates of the prevailing chemical reactions increase exponentially with temperature, graphite gasification at high temperatures is limited by the oxygen diffusion through the boundary layer. The effective diffusion velocity depends on the total flow rate and pressure of the bulk air-gas mixture. This paper develops a semi-empirical Sherwood number correlation for calculating the oxygen diffusion velocity. The correlation is based on a compiled database of the results of convective heat transfer experiments with wires and cylinders of different diameters in air, water and paraffin oil at 0.006 {<=} Re {<=} 1,604 and 0.068 {<=} Sc {<=} 35.2, and of mass transfer experiments at 4.8 {<=} Re {<=} 77 and 1,300 {<=} Sc {<=} 2,000. The developed correlation is within {+-} 8% of the compiled database of 567 data points and consistent with reported gasification rate measurements at higher temperatures in experiments using different size specimens of nuclear graphite grades of NBG-18 and NB-25, IG-11, IG-110 and IG-430 in atmospheric air at 0.08 {<=} Re {<=} 30. Unlike the Graetz solution that gives a constant Sh of 3.66 at Re {<=} 1.0, the present correlation shows Sh decreases monotonically to much lower values with decreasing Re. (authors)

  6. Anomalous dissipation and kinetic-energy distribution in pipes at very high Reynolds numbers.

    PubMed

    Chen, Xi; Wei, Bo-Bo; Hussain, Fazle; She, Zhen-Su

    2016-01-01

    A symmetry-based theory is developed for the description of (streamwise) kinetic energy K in turbulent pipes at extremely high Reynolds numbers (Re's). The theory assumes a mesolayer with continual deformation of wall-attached eddies which introduce an anomalous dissipation, breaking the exact balance between production and dissipation. An outer peak of K is predicted above a critical Re of 10^{4}, in good agreement with experimental data. The theory offers an alternative explanation for the recently discovered logarithmic distribution of K. The concept of anomalous dissipation is further supported by a significant modification of the k-ω equation, yielding an accurate prediction of the entire K profile. PMID:26871016

  7. Implications of turbulence interactions: A path toward addressing very high Reynolds number flows

    SciTech Connect

    Zhou, Y

    2006-05-15

    The classical 'turbulence problem' is narrowed down and redefined for scientific and engineering applications. From an application perspective, accurate computation of large-scale transport of the turbulent flows is needed. In this paper, a scaling analysis that allows for the large-scales of very high Reynolds number turbulent flows - to be handled by the available supercomputers is proposed. Current understanding of turbulence interactions of incompressible turbulence, which forms the foundation of our argument, is reviewed. Furthermore, the data redundancy in the inertial range is demonstrated. Two distinctive interactions, namely, the distance and near-grid interactions, are inspected for large-scale simulations. The distant interactions in the subgrid scales in an inertial range can be effectively modelled by an eddy damping. The near-grid interactions must be carefully incorporated.

  8. Experimental Investigation of Primary and Secondary Features in High-Mach-Number Shock-Bubble Interaction

    NASA Astrophysics Data System (ADS)

    Ranjan, Devesh; Niederhaus, John; Motl, Bradley; Anderson, Mark; Oakley, Jason; Bonazza, Riccardo

    2007-01-01

    Experiments to study the compression and unstable evolution of an isolated soap-film bubble containing helium, subjected to a strong planar shock wave (M=2.95) in ambient nitrogen, have been performed in a vertical shock tube of square internal cross section using planar laser diagnostics. The early phase of the interaction process is dominated by the formation of a primary vortex ring due to the baroclinic source of vorticity deposited during the shock-bubble interaction, and the mass transfer from the body of the bubble to the vortex ring. The late time (long after shock interaction) study reveals the presence of a secondary baroclinic source of vorticity at high Mach number which is responsible for the formation of counterrotating secondary and tertiary vortex rings and the subsequent larger rate of elongation of the bubble.

  9. Analogies Between Colloidal Sedimentation and Turbulent Convection at High Prandtl Numbers

    NASA Technical Reports Server (NTRS)

    Tong, P.; Ackerson, B. J.

    1999-01-01

    A new set of coarse-grained equations of motion is proposed to describe concentration and velocity fluctuations in a dilute sedimenting suspension of non-Brownian particles. With these equations, colloidal sedimentation is found to be analogous to turbulent convection at high Prandtl numbers. Using Kraichnan's mixing-length theory, we obtain scaling relations for the diffusive dissipation length delta(sub theta), the velocity variance delta u, and the concentration variance delta phi. The obtained scaling laws over varying particle radius alpha and volume fraction phi(sub ) are in excellent agreement with the recent experiment by Segre, Herbolzheimer, and Chaikin. The analogy between colloidal sedimentation and turbulent convection gives a simple interpretation for the existence of a velocity cut-off length, which prevents hydrodynamic dispersion coefficients from being divergent. It also provides a coherent framework for the study of sedimentation dynamics in different colloidal systems.

  10. Particle-number conserving analysis of the high-spin structure of 159Ho

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen-Hua

    2016-05-01

    The high-spin rotational bands in odd-Z nuclei 159Ho (Z = 67) are investigated using the cranked shell model with the pairing correlations treated by a particle-number conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency ħω are reproduced very well by the calculations. The splitting between the signature partners of the yrast band 7 /2- [ 523 ] is discussed and the splitting of the excited band 7 /2+ [ 404 ] above ħω ∼ 0.30 MeV is predicted due to the level crossing with 1 /2+ [ 411 ]. The calculated B (E 2) transition probabilities are also suggested for future experiments.

  11. Preliminary engineering study: Quick opening valve MSFC high Reynolds number wind tunnel

    NASA Technical Reports Server (NTRS)

    1983-01-01

    FluiDyne Engineering Corporation has conducted a preliminary engineering study of a quick-opening valve for the MSFC High Reynolds Number Wind Tunnel under NASA Contract NAS8-35056. The subject valve is intended to replace the Mylar diaphragm system as the flow initiation device for the tunnel. Only valves capable of opening within 0.05 sec. and providing a minimum of 11.4 square feet of flow area were considered. Also, the study focused on valves which combined the quick-opening and tight shutoff features in a single unit. A ring sleeve valve concept was chosen for refinement and pricing. Sealing for tight shutoff, ring sleeve closure release and sleeve actuation were considered. The resulting cost estimate includes the valve and requisite modifications to the facility to accommodate the valve as well as the associated design and development work.

  12. High-order simulations of low Reynolds number membrane airfoils under prescribed motion

    NASA Astrophysics Data System (ADS)

    Jaworski, Justin W.; Gordnier, Raymond E.

    2012-05-01

    The aerodynamics and aeroelastic response of a membrane wing under prescribed motion are investigated using a high-order, two-dimensional Navier-Stokes solver coupled to a geometrically nonlinear membrane model. The impact of increasing Reynolds number on the vortex dynamics and unsteady aerodynamic loads is examined for moderate-amplitude plunge and combined pitch-plunge motions at low frequency. Simulation results are compared with classical thin airfoil theory and highlight the differences between rigid and flexible membrane airfoils undergoing small and moderate amplitude motions. The present study demonstrates the ability of lifting membrane surface flexibility to enhance thrust production and propulsive efficiency, which may inform the design of flapping wing membrane fliers.

  13. Local isotropy in distorted turbulent boundary layers at high Reynolds number

    NASA Technical Reports Server (NTRS)

    Saddoughi, Seyed G.

    1993-01-01

    This is a report on the continuation of our experimental investigations of the hypothesis of local isotropy in shear flows. This hypothesis, which states that at sufficiently high Reynolds numbers the small-scale structures of turbulent motions are independent of large-scale structures and mean deformations, has been used in theoretical studies of turbulence and computational methods such as large-eddy simulation. Since Kolmogorov proposed his theory, there have been many experiments, conducted in wakes, jets, mixing layers, a tidal channel, and atmospheric and laboratory boundary layers, in which attempts have been made to verify - or refute - the local-isotropy hypothesis. However, a review of the literature over the last five decades indicated that, despite all these experiments in shear flows, there was no consensus in the scientific community regarding this hypothesis, and, therefore, it seemed worthwhile to undertake a fresh experimental investigation into this question.

  14. Dissipative particle dynamics of diffusion-NMR requires high Schmidt-numbers.

    PubMed

    Azhar, Mueed; Greiner, Andreas; Korvink, Jan G; Kauzlarić, David

    2016-06-28

    We present an efficient mesoscale model to simulate the diffusion measurement with nuclear magnetic resonance (NMR). On the level of mesoscopic thermal motion of fluid particles, we couple the Bloch equations with dissipative particle dynamics (DPD). Thereby we establish a physically consistent scaling relation between the diffusion constant measured for DPD-particles and the diffusion constant of a real fluid. The latter is based on a splitting into a centre-of-mass contribution represented by DPD, and an internal contribution which is not resolved in the DPD-level of description. As a consequence, simulating the centre-of-mass contribution with DPD requires high Schmidt numbers. After a verification for fundamental pulse sequences, we apply the NMR-DPD method to NMR diffusion measurements of anisotropic fluids, and of fluids restricted by walls of microfluidic channels. For the latter, the free diffusion and the localisation regime are considered. PMID:27369491

  15. Dissipative particle dynamics of diffusion-NMR requires high Schmidt-numbers

    NASA Astrophysics Data System (ADS)

    Azhar, Mueed; Greiner, Andreas; Korvink, Jan G.; Kauzlarić, David

    2016-06-01

    We present an efficient mesoscale model to simulate the diffusion measurement with nuclear magnetic resonance (NMR). On the level of mesoscopic thermal motion of fluid particles, we couple the Bloch equations with dissipative particle dynamics (DPD). Thereby we establish a physically consistent scaling relation between the diffusion constant measured for DPD-particles and the diffusion constant of a real fluid. The latter is based on a splitting into a centre-of-mass contribution represented by DPD, and an internal contribution which is not resolved in the DPD-level of description. As a consequence, simulating the centre-of-mass contribution with DPD requires high Schmidt numbers. After a verification for fundamental pulse sequences, we apply the NMR-DPD method to NMR diffusion measurements of anisotropic fluids, and of fluids restricted by walls of microfluidic channels. For the latter, the free diffusion and the localisation regime are considered.

  16. Double large field stereoscopic PIV in a high Reynolds number turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Coudert, S.; Foucaut, J. M.; Kostas, J.; Stanislas, M.; Braud, P.; Fourment, C.; Delville, J.; Tutkun, M.; Mehdi, F.; Johansson, P.; George, W. K.

    2011-01-01

    An experiment on a flat plate turbulent boundary layer at high Reynolds number has been carried out in the Laboratoire de Mecanique de Lille (LML, UMR CNRS 8107) wind tunnel. This experiment was performed jointly with LEA (UMR CNRS 6609) in Poitiers (France) and Chalmers University of Technology (Sweden), in the frame of the WALLTURB European project. The simultaneous recording of 143 hot wires in one transverse plane and of two perpendicular stereoscopic PIV fields was performed successfully. The first SPIV plane is 1 cm upstream of the hot wire rake and the second is both orthogonal to the first one and to the wall. The first PIV results show a blockage effect which based on both statistical results (i.e. mean, RMS and spatial correlation) and a potential model does not seem to affect the turbulence organization.

  17. Drag coefficient of the weakly ionized plasma in the high Knudsen number regime

    SciTech Connect

    Chu, H.-Y.; Si, M.-C.; Lin, S.-B.

    2009-06-15

    The drag force acting on a micron-sized polystyrene particle in the high Knudsen number regime is investigated. Analysis of the particle trajectories in stationary neutral argon gas environment suggests the damping time constant {tau}{proportional_to}p{sup -1.20{+-}}{sup 0.04} and Epstein drag force coefficient {delta}=1.40. The neutral drag coefficient is compared with the drag coefficient measurement in dust-free plasma. The phenomena of the reduced drag in weakly viscous and weakly ionized rf plasma are also observed in this report. It is shown that the slight changes in rf power and pressure would enhance the reduced drag effect, which suggests that there is an additional electrostatic force acting along the particle motion in the plasma.

  18. High Reynolds number droplet de-pinning on textured surfaces: theory and experiments

    NASA Astrophysics Data System (ADS)

    Lee, Sungyon; Wilcox, Benjamin; Xu, Feng; White, Edward

    2014-11-01

    The stability of drops on surfaces subject to forcing by wind and gravity is relevant to heat exchangers, fuel cells, and aircraft icing, and it lacks understanding in a high Reynolds number regime. To experimentally investigate this phenomenon, water drops are placed on the rough aluminum floor of a tiltable wind tunnel and brought to critical conditions for varying drop sizes, inclination angles, and flow speeds. In particular, the evolving 3D droplet shapes under flow are reconstructed based on a laser-speckle interface measurement tool, while the critical flow rates of droplet depinning are also noted. By accounting for the contact angle hysteresis and the pressure build-up in a nearly turbulent boundary layer, the critical depinning flow rate is theoretically predicted and is compared to the experimental results. We also observe and explain the transition of the drop depinning behavior from inertia-dominated to gravity-dominated regimes at non-zero inclination angles.

  19. Kinetic energy and scalar spectra in high Rayleigh number axially homogeneous buoyancy driven turbulence

    NASA Astrophysics Data System (ADS)

    Pawar, Shashikant S.; Arakeri, Jaywant H.

    2016-06-01

    Kinetic energy and scalar spectra from the measurements in high Rayleigh number axially homogeneous buoyancy driven turbulent flow are presented. Kinetic energy and concentration (scalar) spectra are obtained from the experiments wherein density difference is created using brine and fresh water and temperature spectra are obtained from the experiments in which heat is used. Scaling of the frequency spectra of lateral and longitudinal velocity near the tube axis is closer to the Kolmogorov-Obukhov scaling, while the scalar spectra show some evidence of dual scaling, Bolgiano-Obukhov scaling followed by Obukhov-Corrsin scaling. These scalings are also observed in the corresponding second order spatial structure functions of velocity and concentration fluctuations.

  20. The variational multiscale element free Galerkin method for MHD flows at high Hartmann numbers

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Ouyang, Jie; Zhang, Xiaohua

    2013-04-01

    The aim of the paper is the development of an efficient numerical algorithm for the solution of magnetohydrodynamics (MHD) flow problems with either fully insulating walls or partially insulating and partially conducting walls. Toward this, we first extend the influence domain of the shape function for the element free Galerkin (EFG) method to have arbitrary shape. When the influence factor approaches 1, we find that the EFG shape function almost has the Delta property at the node (i.e. the value of the EFG shape function of the node is nearly equal to 1 at the position of this node) as well as the property of slices in the influence domain of the node (i.e. the EFG shape function in the influence domain of the node is nearly constructed by different functions defined in different slices). Therefore, for MHD flow problems at high Hartmann numbers we follow the idea of the variational multiscale finite element method (VMFEM) to combine the EFG method with the variational multiscale (VM) method, namely the variational multiscale element free Galerkin (VMEFG) method is proposed. Subsequently, in order to validate the proposed method, we compare the obtained approximate solutions with the exact solutions for some problems where such exact solutions are known. Finally, several benchmark problems of MHD flows are simulated and the numerical results indicate that the VMEFG method is stable at moderate and high values of Hartmann number. Another important feature of this method is that the stabilization parameter has appeared naturally via the solution of the fine scale problem. Meanwhile, because this proposed method is a type of meshless method, it can avoid the need for meshing, a very demanding task for complicated geometry problems.

  1. The Spectral Amplitude of Stellar Convection and Its Scaling in the High-Rayleigh-number Regime

    NASA Astrophysics Data System (ADS)

    Featherstone, Nicholas A.; Hindman, Bradley W.

    2016-02-01

    Convection plays a central role in the dynamics of any stellar interior, and yet its operation remains largely hidden from direct observation. As a result, much of our understanding concerning stellar convection necessarily derives from theoretical and computational models. The Sun is, however, exceptional in that regard. The wealth of observational data afforded by its proximity provides a unique test bed for comparing convection models against observations. When such comparisons are carried out, surprising inconsistencies between those models and observations become apparent. Both photospheric and helioseismic measurements suggest that convection simulations may overestimate convective flow speeds on large spatial scales. Moreover, many solar convection simulations have difficulty reproducing the observed solar differential rotation owing to this apparent overestimation. We present a series of three-dimensional stellar convection simulations designed to examine how the amplitude and spectral distribution of convective flows are established within a star’s interior. While these simulations are nonmagnetic and nonrotating in nature, they demonstrate two robust phenomena. When run with sufficiently high Rayleigh number, the integrated kinetic energy of the convection becomes effectively independent of thermal diffusion, but the spectral distribution of that kinetic energy remains sensitive to both of these quantities. A simulation that has converged to a diffusion-independent value of kinetic energy will divide that energy between spatial scales such that low-wavenumber power is overestimated and high-wavenumber power is underestimated relative to a comparable system possessing higher Rayleigh number. We discuss the implications of these results in light of the current inconsistencies between models and observations.

  2. Observations of high droplet number concentrations in Southern Ocean boundary layer clouds

    NASA Astrophysics Data System (ADS)

    Chubb, T.; Huang, Y.; Jensen, J.; Campos, T.; Siems, S.; Manton, M.

    2015-09-01

    Data from the standard cloud physics payload during the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) campaigns provide a snapshot of unusual wintertime microphysical conditions in the boundary layer over the Southern Ocean. On 29 June 2011, the HIAPER sampled the boundary layer in a region of pre-frontal warm air advection between 58 and 48° S to the south of Tasmania. Cloud droplet number concentrations were consistent with climatological values in the northernmost profiles but were exceptionally high for wintertime in the Southern Ocean at 100-200 cm-3 in the southernmost profiles. Sub-micron (0.0625 m s-1) were most likely responsible for production of sea spray aerosol which influenced the microphysical properties of the boundary layer clouds. The smaller size and higher number concentration of cloud droplets is inferred to increase the albedo of these clouds, and these conditions occur regularly, and are expected to increase in frequency, over windy parts of the Southern Ocean.

  3. Mathematics for High School. Intermediate Mathematics, Part 1, Supplementary Unit I. The Development of the Real Number System. Revised Edition.

    ERIC Educational Resources Information Center

    Allen, Frank B.; And Others

    This is a supplementary unit to Mathematics for High School, Intermediate Mathematics, Part 1. In this publication, real numbers and rules for operating them are examined. The study begins by examining whole numbers and some of the properties of addition and multiplication of whole numbers. Most of the basic rules for algebra are developed from…

  4. Highly conformal CT based surface mould brachytherapy for non-melanoma skin cancers of earlobe and nose

    PubMed Central

    Kozłowski, Sławomir; Pietraszek, Andrzej; Pietrzykowska-Kuncman, Malwina; Danielska, Justyna; Sobotkowski, Janusz; Łuniewska-Bury, Jolanta; Fijuth, Jacek

    2016-01-01

    Purpose Brachytherapy (BT), due to rapid dose fall off and minor set-up errors, should be superior to external beam radiotherapy (EBRT) for treatment of lesions in difficult locations like nose and earlobe. Evidences in this field are scarce. We describe computed tomography (CT) based surface mould BT for non-melanoma skin cancers (NMSC), and compare its conformity, dose coverage, and tissue sparing ability to EBRT. Material and methods We describe procedure of preparation of surface mould applicator and dosimetry parameters of BT plans, which were implemented in 10 individuals with NMSC of nose and earlobe. We evaluated dose coverage by minimal dose to 90% of planning target volume (PTV) (D90), volumes of PTV receiving 90-150% of prescribed dose (PD) (VPTV90-150), conformal index for 90 and 100% of PD (COIN90, COIN100), dose homogeneity index (DHI), dose nonuniformity ratio (DNR), exposure of organs. Prospectively, we created CT-based photons and electrons plans. We compared conformity (COIN90, COIN100), dose coverage of PTV (D90, VPTV90, VPTV100), volumes of body receiving 10-90% of PD (V10-V90) of EBRT and BT plans. Results We obtained mean BT-DHI = 0.76, BT-DNR = 0.23, EBRT-DHI = 1.26. We observed no significant differences in VPTV90 and D90 between BT and EBRT. Mean BT-VPTV100 (89.4%) was higher than EBRT-VPTV100 (71.2%). Both COIN90 (BT-COIN90 = 0.46 vs. EBRT-COIN90 = 0.21) and COIN100 (BT-COIN100 = 0.52 vs. EBRT-COIN100 = 0.26) were superior for BT plans. We observed more exposure of normal tissues for small doses in BT plans (V10, V20), for high doses in EBRT plans (V70, V90). Conclusions Computed tmography-based surface mould brachytherapy for superficial lesions on irregular surfaces is a highly conformal method with good homogeneity. Brachytherapy is superior to EBRT in those locations in terms of conformity and normal tissue sparing ability in high doses. PMID:27504128

  5. High quality copy number and genotype data from FFPE samples using Molecular Inversion Probe (MIP) microarrays

    SciTech Connect

    Wang, Yuker; Carlton, Victoria E.H.; Karlin-Neumann, George; Sapolsky, Ronald; Zhang, Li; Moorhead, Martin; Wang, Zhigang C.; Richardson, Andrea L.; Warren, Robert; Walther, Axel; Bondy, Melissa; Sahin, Aysegul; Krahe, Ralf; Tuna, Musaffe; Thompson, Patricia A.; Spellman, Paul T.; Gray, Joe W.; Mills, Gordon B.; Faham, Malek

    2009-02-24

    A major challenge facing DNA copy number (CN) studies of tumors is that most banked samples with extensive clinical follow-up information are Formalin-Fixed Paraffin Embedded (FFPE). DNA from FFPE samples generally underperforms or suffers high failure rates compared to fresh frozen samples because of DNA degradation and cross-linking during FFPE fixation and processing. As FFPE protocols may vary widely between labs and samples may be stored for decades at room temperature, an ideal FFPE CN technology should work on diverse sample sets. Molecular Inversion Probe (MIP) technology has been applied successfully to obtain high quality CN and genotype data from cell line and frozen tumor DNA. Since the MIP probes require only a small ({approx}40 bp) target binding site, we reasoned they may be well suited to assess degraded FFPE DNA. We assessed CN with a MIP panel of 50,000 markers in 93 FFPE tumor samples from 7 diverse collections. For 38 FFPE samples from three collections we were also able to asses CN in matched fresh frozen tumor tissue. Using an input of 37 ng genomic DNA, we generated high quality CN data with MIP technology in 88% of FFPE samples from seven diverse collections. When matched fresh frozen tissue was available, the performance of FFPE DNA was comparable to that of DNA obtained from matched frozen tumor (genotype concordance averaged 99.9%), with only a modest loss in performance in FFPE. MIP technology can be used to generate high quality CN and genotype data in FFPE as well as fresh frozen samples.

  6. Velocity Resolved---Scalar Modeled Simulations of High Schmidt Number Turbulent Transport

    NASA Astrophysics Data System (ADS)

    Verma, Siddhartha

    The objective of this thesis is to develop a framework to conduct velocity resolved - scalar modeled (VR-SM) simulations, which will enable accurate simulations at higher Reynolds and Schmidt (Sc) numbers than are currently feasible. The framework established will serve as a first step to enable future simulation studies for practical applications. To achieve this goal, in-depth analyses of the physical, numerical, and modeling aspects related to Sc " 1 are presented, specifically when modeling in the viscous-convective subrange. Transport characteristics are scrutinized by examining scalar-velocity Fourier mode interactions in Direct Numerical Simulation (DNS) datasets and suggest that scalar modes in the viscous-convective subrange do not directly affect large-scale transport for high Sc . Further observations confirm that discretization errors inherent in numerical schemes can be sufficiently large to wipe out any meaningful contribution from subfilter models. This provides strong incentive to develop more effective numerical schemes to support high Sc simulations. To lower numerical dissipation while maintaining physically and mathematically appropriate scalar bounds during the convection step, a novel method of enforcing bounds is formulated, specifically for use with cubic Hermite polynomials. Boundedness of the scalar being transported is effected by applying derivative limiting techniques, and physically plausible single sub-cell extrema are allowed to exist to help minimize numerical dissipation. The proposed bounding algorithm results in significant performance gain in DNS of turbulent mixing layers and of homogeneous isotropic turbulence. Next, the combined physical/mathematical behavior of the subfilter scalar-flux vector is analyzed in homogeneous isotropic turbulence, by examining vector orientation in the strain-rate eigenframe. The results indicate no discernible dependence on the modeled scalar field, and lead to the identification of the tensor

  7. Measurements of high number densities of ice crystals in the tops of tropical cumulonimbus

    NASA Astrophysics Data System (ADS)

    Knollenberg, R. G.; Kelly, K.; Wilson, J. C.

    1993-05-01

    Imaging and light scattering instruments were used during the January/February 1987 STEP Tropical Experiment at Darwin, Australia, to measure ice crystal size distributions in the tops of tropical cumulonimbus anvils associated with tropical cyclones and related cloud systems. Two light scattering instruments covered particles from 0.1-μm to 78-μm diameter. Particles larger than 50-μm diameter were imaged with a two-dimensional Grey optical array imaging probe. The measurements were made at altitudes ranging from 13 to 18 km at temperatures ranging from -60° to -90°C. Additional measurements made in continental cumulonimbus anvils in the western United States offer a comparative data set. The tropical anvil penetrations revealed surprisingly high concentrations of ice crystals. Number densities were typically greater than 10 cm-3 with up to 100 cm-3 if one includes all particles larger than 0.1 μm and can approach condensation nuclei in total concentration. In order to explain the high number densities, ice crystal nucleation at altitude is proposed with the freezing of fairly concentrated solution droplets in equilibrium at low relative humidities. Any dilute liquid phase is hypothesized to be transitory with a vanishingly short lifetime and limited to cloud levels nearer -40°C. Homogeneous nucleation of ice involving H2SO4 nuclei is attractive in explaining the high number densities of small ice crystals observed near cloud top at temperatures below -60°C. The tropical size distributions were converted to mass using a spherical equivalent size, while the continental anvil data were treated as crystalline plates. Comparisons of the ice water contents integrated from the mass distributions with total water contents measured with NOAA Lyman-alpha instruments require bulk densities equivalent to solid ice for best agreement. Correlation between the two data sets for a number of flight passes was quite good and was further improved by subtraction of water

  8. The effect of hydrodynamic interactions on the average properties of a bidisperse suspension of high Reynolds number, low Weber number bubbles

    NASA Astrophysics Data System (ADS)

    Kumaran, V.; Koch, Donald L.

    1993-05-01

    The hydrodynamic interaction between a pair of nondeformable bubbles (low Weber number limit) in potential flow (high Reynolds number limit) was analyzed. The velocity potential was determined using twin spherical expansions, and the equations of motion were calculated by enforcing the zero net force condition on the surface of the bubbles. The acceleration due to the interaction is expressed in a perturbation series in the parameter (ai/R), where ai is the radius of bubble i, R is the distance between the bubbles, and the leading-order acceleration was found to decrease as (ai/R)4. The effect of potential flow interactions on the trajectory of a pair of bubbles of different sizes (size ratio greater than 1.07 at a Reynolds number of 200) rising due to gravity was studied. A salient feature of the trajectories is that the surfaces of the bubble do not come into contact during the interaction, except when the smaller bubble radius is less than 0.233 times the larger bubble radius when the Reynolds number based on the larger bubble is 200. In the latter case, however, the Reynolds number based on the radius of the smaller bubble is not large enough to justify the potential flow approximation. For interactions where collisions do not occur, the mean-square fluctuating velocity in a uniform suspension and the hydrodynamic diffusivities in a nonuniform suspension were calculated by performing an ensemble average over pair interactions. The pair averaging procedure is valid for dilute suspensions (V≪18/Re, where V is the volume fraction of the bubbles and Re is the Reynolds number based on the bubble radius and its terminal velocity).

  9. Changes in intracortical microporosities induced by pharmaceutical treatment of osteoporosis as detected by high resolution micro-CT

    SciTech Connect

    Tommasini S. M.; Miller L.; Trinward, A.; Acerbo, A.S.; De Carlo F. and Judex, S.

    2011-12-28

    Bone's microporosities play important biologic and mechanical roles. Here, we quantified 3D changes in cortical osteocyte-lacunae and other small porosities induced by estrogen withdrawal and two different osteoporosistreatments. Unlike 2D measurements, these data collected via synchrotron radiation-based {mu}CT describe the size and 3D spatial distribution of a large number of porous structures. Six-month old female Sprague-Dawley rats were separated into four groups of age-matched controls, untreated OVX, OVX treated with PTH, and OVX treated with Alendronate (ALN). Intracortical microporosity of the medial quadrant of the femoral diaphysis was quantified at endosteal, intracortical, and periosteal regions of the samples, allowing the quantification of osteocyte lacunae that were formed primarily before versus after the start of treatment. Across the overall thickness of the medial cortex, lacunar volume fraction (Lc.V/TV) was significantly lower in ALN treated rats compared to PTH. In the endosteal region, average osteocyte lacunar volume (< Lc.V >) of untreated OVX rats was significantly lower than in age-matched controls, indicating a decrease in osteocyte lacunar size in bone formed on the endosteal surface after estrogen withdrawal. The effect of treatment (OVX, ALN, PTH) on the number of lacunae per tissue volume (Lc.N/TV) was dependent on the specific location within the cortex (endosteal, intracortical, periosteal). In both the endosteal and intracortical regions, Lc.N/TV was significantly lower in ALN than in untreated OVX, suggesting a site-specific effect in osteocyte lacuna density with ALN treatment. There also were a significantly greater number of small pores (5-100 {micro}m{sup 3} in volume) in the endosteal region for PTH compared to ALN. The mechanical impact of this altered microporosity structure is unknown, but might serve to enhance, rather than deteriorate bone strength with PTH treatment, as smaller osteocyte lacunae may be better able to

  10. Changes in Intracortical Microporosities Induced by Pharmaceutical Treatment of Osteoporosis as Detected by High Resolution Micro-CT

    PubMed Central

    Tommasini, Steven M.; Trinward, Andrea; Acerbo, Alvin S.; De Carlo, Francesco; Miller, Lisa M.; Judex, Stefan

    2012-01-01

    Bone’s microporosities play important biologic and mechanical roles. Here, we quantified 3D changes in cortical osteocyte-lacunae and other small porosities induced by estrogen withdrawal and two different osteoporosis treatments. Unlike 2D measurements, these data collected via synchrotron radiation-based μCT describe the size and 3D spatial distribution of a large number of porous structures. Six-month old female Sprague-Dawley rats were separated into four groups of age-matched controls, untreated OVX, OVX treated with PTH, and OVX treated with Alendronate (ALN). Intracortical microporosity of the medial quadrant of the femoral diaphysis was quantified at endosteal, intracortical, and periosteal regions of the samples, allowing the quantification of osteocyte lacunae that were formed primarily before versus after the start of treatment. Across the overall thickness of the medial cortex, lacunar volume fraction (Lc.V/TV) was significantly lower in ALN treated rats compared to PTH. In the endosteal region, average osteocyte lacunar volume () of untreated OVX rats was significantly lower than in age-matched controls, indicating a decrease in osteocyte lacunar size in bone formed on the endosteal surface after estrogen withdrawal. The effect of treatment (OVX, ALN, PTH) on the number of lacunae per tissue volume (Lc.N/TV) was dependent on the specific location within the cortex (endosteal, intracortical, periosteal). In both the endosteal and intracortical regions, Lc.N/TV was significantly lower in ALN than in untreated OVX, suggesting a site-specific effect in osteocyte lacuna density with ALN treatment. There also were a significantly greater number of small pores (5–100 μm3 in volume) in the endosteal region for PTH compared to ALN. The mechanical impact of this altered microporosity structure is unknown, but might serve to enhance, rather than deteriorate bone strength with PTH treatment, as smaller osteocyte lacunae may be better able to absorb

  11. Spiral CT: vascular applications.

    PubMed

    Rankin, S C

    1998-08-01

    Recent technical advances in CT have renewed interest in the development of CT angiography (CTA). CT angiography is a minimally invasive method of visualising the vascular system and is becoming an alternative to conventional arteriography in some situations. Spiral technology allows a volume of data to be obtained on a single breath-hold with no respiratory misregistration. Fast machines with second or subsecond acquisition times mean the images are obtained while there are high circulating levels of contrast medium giving peak vascular opacification from a peripheral intravenous injection. Accurate timing will ensure either the arterial or venous phase is imaged. Multiple overlapping axial images can be obtained from the data set with no increase in radiation dose to the patient and from these scans computer generated multiplanar and 3D images are obtained which can be viewed from numerous angles. CT angiography can be performed more quickly, less invasively and at reduced cost compared to conventional angiography. PMID:9717621

  12. Using high time resolution aerosol and number size distribution measurements to estimate atmospheric extinction.

    PubMed

    Malm, William C; McMeeking, Gavin R; Kreidenweis, Sonia M; Levin, Ezra; Carrico, Christian M; Day, Derek E; Collett, Jeffrey L; Lee, Taehyoung; Sullivan, Amy P; Raja, Suresh

    2009-09-01

    Rocky Mountain National Park is experiencing reduced visibility and changes in ecosystem function due to increasing levels of oxidized and reduced nitrogen. The Rocky Mountain Atmospheric Nitrogen and Sulfur (RoMANS) study was initiated to better understand the origins of sulfur and nitrogen species as well as the complex chemistry occurring during transport from source to receptor. As part of the study, a monitoring program was initiated for two 1-month time periods--one during the spring and the other during late summer/fall. The monitoring program included intensive high time resolution concentration measurements of aerosol number size distribution, inorganic anions, and cations, and 24-hr time resolution of PM2.5 and PM10 mass, sulfate, nitrate, carbon, and soil-related elements concentrations. These data are combined to estimate high time resolution concentrations of PM2.5 and PM10 aerosol mass and fine mass species estimates of ammoniated sulfate, nitrate, and organic and elemental carbon. Hour-by-hour extinction budgets are calculated by using these species concentration estimates and measurements of size distribution and assuming internal and external particle mixtures. Summer extinction was on average about 3 times higher than spring extinction. During spring months, sulfates, nitrates, carbon mass, and PM10 - PM2.5 mass contributed approximately equal amounts of extinction, whereas during the summer months, carbonaceous material extinction was 2-3 times higher than other species. PMID:19785272

  13. Radiative Properties of High Wire Number Tungsten Arrays with Implosion Times up to 250 ns

    SciTech Connect

    Beg, F.N.; Coverdale, C.A.; Deeney, C.; Douglas, M.R.; Haines, M.G.; Peterson, D.L.; Roderick, N.F.; Ruiz-Camacho, J.; Spielman, R.B.; Struve, K.W.; Stygar, W.A.

    1999-02-02

    High wire number, 25-mm diameter tungsten wire arrays have been imploded on the 8-MA Saturn generator, operating in a long-pulse mode. By varying the mass load from 710 to 6140 ps/cm, implosion times of 130 to 250 ns have been obtained with implosion velocities of 50 to 25 cn-dys, respectively. These z-pinch implosions produced plasmas with millimeter diameters that radiated 600 to 800 kJ of x-rays, with powers of 20 to 49 TW; the corresponding pulse widths were 19 to 7.5 ns, with risetimes ranging from 6.5 to 4.0 ns. These powers and pulse widths are similar to those achieved with 50 ns implosion times on Saturn. Two-dimensional, radiation- magnetohydrodynamic calculations indicate that the imploding shells in these long implosion time experiments are comparable in width to those in the short pulse cases. This can only be due to lower initial perturbations. A heuristic wire array model suggests that the reduced perturbations, in the long pulse cases, may be due to the individual wire merger occurring well before the acceleration of the shell. The experiments and modeling suggest that 150 to 200 ns implosion time z-pinches could be employed for high-power, x-ray source applications.

  14. A Study of the Unstable Modes in High Mach Number Gaseous Jets and Shear Layers

    NASA Astrophysics Data System (ADS)

    Bassett, Gene Marcel

    1993-01-01

    Instabilities affecting the propagation of supersonic gaseous jets have been studied using high resolution computer simulations with the Piecewise-Parabolic-Method (PPM). These results are discussed in relation to jets from galactic nuclei. These studies involve a detailed treatment of a single section of a very long jet, approximating the dynamics by using periodic boundary conditions. Shear layer simulations have explored the effects of shear layers on the growth of nonlinear instabilities. Convergence of the numerical approximations has been tested by comparing jet simulations with different grid resolutions. The effects of initial conditions and geometry on the dominant disruptive instabilities have also been explored. Simulations of shear layers with a variety of thicknesses, Mach numbers and densities perturbed by incident sound waves imply that the time for the excited kink modes to grow large in amplitude and disrupt the shear layer is taug = (546 +/- 24) (M/4)^{1.7 } (Apert/0.02) ^{-0.4} delta/c, where M is the jet Mach number, delta is the half-width of the shear layer, and A_ {pert} is the perturbation amplitude. For simulations of periodic jets, the initial velocity perturbations set up zig-zag shock patterns inside the jet. In each case a single zig-zag shock pattern (an odd mode) or a double zig-zag shock pattern (an even mode) grows to dominate the flow. The dominant kink instability responsible for these shock patterns moves approximately at the linear resonance velocity, nu_ {mode} = cextnu_ {relative}/(cjet + c_ {ext}). For high resolution simulations (those with 150 or more computational zones across the jet width), the even mode dominates if the even penetration is higher in amplitude initially than the odd perturbation. For low resolution simulations, the odd mode dominates even for a stronger even mode perturbation. In high resolution simulations the jet boundary rolls up and large amounts of external gas are entrained into the jet. In low

  15. The effect of pore throat size and injection flowrate on the determination and sensitivity of different capillary number values at high-capillary-number flow in porous media

    NASA Astrophysics Data System (ADS)

    Yadali Jamaloei, Benyamin; Ahmadloo, Farid; Kharrat, Riyaz

    2010-10-01

    This study examines the effect of pore throat size and injection flowrate on the values of the pore-scale capillary number, the Newtonian-fluid capillary number and the apparent capillary number (Nc1, Nc2 and Nc3, respectively) and their sensitivity to change in high-capillary-number flow through porous media, which occurs in polymer-assisted dilute surfactant flooding (PADSF). Additionally, the influence of pore throat size and injection flowrate on oil recovery at breakthrough and at the end of displacement (ultimate) and the relationship between the effective shear rate γeff and the porous medium-dependent shift factor α are discussed. The results indicated that Nc2 was the smallest and Nc3 was the largest value. The difference between Nc2 and Nc3 is due to the increase in apparent viscosity of the polymer-contained surfactant solution during the flow through porous media and the change in Nc3 should be utilized to characterize the macroscopic behavior of the PADSF. Generally, the decrease in pore throat size and the increase in injection flowrate caused an increase in the ultimate oil recovery and Nc3. Moreover, the oil recovery at breakthrough decreased with an increase in pore throat size and injection flowrate. Finally, the rate of change of γeff, with change in α, increased almost uniformly with a decrease in pore throat size and an increase in injection flowrate.

  16. N-231 High Reynolds Number Channel Facility (An example of a Versatile Wind Tunnel) Tunnel 1 I is a

    NASA Technical Reports Server (NTRS)

    1980-01-01

    N-231 High Reynolds Number Channel Facility (An example of a Versatile Wind Tunnel) Tunnel 1 I is a blowdown Facility that utilizes interchangeable test sections and nozzles. The facility provides experimental support for the fluid mechanics research, including experimental verification of aerodynamic computer codes and boundary-layer and airfoil studies that require high Reynolds number simulation. (Tunnel 1)

  17. CT scan

    MedlinePlus

    ... that slides into the center of the CT scanner. Once you are inside the scanner, the machine's x-ray beam rotates around you. Modern spiral scanners can perform the exam without stopping. A computer ...

  18. Patient doses from CT examinations in Turkey

    PubMed Central

    Ataç, Gökçe Kaan; Parmaksız, Aydın; İnal, Tolga; Bulur, Emine; Bulgurlu, Figen; Öncü, Tolga; Gündoğdu, Sadi

    2015-01-01

    PURPOSE We aimed to establish the first diagnostic reference levels (DRLs) for computed tomography (CT) examinations in adult and pediatric patients in Turkey and compare these with international DRLs. METHODS CT performance information and examination parameters (for head, chest, high-resolution CT of the chest [HRCT-chest], abdominal, and pelvic protocols) from 1607 hospitals were collected via a survey. Dose length products and effective doses for standard patient sizes were calculated from the reported volume CT dose index (CTDIvol). RESULTS The median number of protocols reported from the 167 responding hospitals (10% response rate) was 102 across five different age groups. Third quartile CTDIvol values for adult pelvic and all pediatric body protocols were higher than the European Commission standards but were comparable to studies conducted in other countries. CONCLUSION The radiation dose indicators for adult patients were similar to those reported in the literature, except for those associated with head protocols. CT protocol optimization is necessary for adult head and pediatric chest, HRCT-chest, abdominal, and pelvic protocols. The findings from this study are recommended for use as national DRLs in Turkey. PMID:26133189

  19. Ground Boundary Conditions for Thermal Convection Over Horizontal Surfaces at High Rayleigh Numbers

    NASA Astrophysics Data System (ADS)

    Hanjalić, K.; Hrebtov, M.

    2016-07-01

    We present "wall functions" for treating the ground boundary conditions in the computation of thermal convection over horizontal surfaces at high Rayleigh numbers using coarse numerical grids. The functions are formulated for an algebraic-flux model closed by transport equations for the turbulence kinetic energy, its dissipation rate and scalar variance, but could also be applied to other turbulence models. The three-equation algebraic-flux model, solved in a T-RANS mode ("Transient" Reynolds-averaged Navier-Stokes, based on triple decomposition), was shown earlier to reproduce well a number of generic buoyancy-driven flows over heated surfaces, albeit by integrating equations up to the wall. Here we show that by using a set of wall functions satisfactory results are found for the ensemble-averaged properties even on a very coarse computational grid. This is illustrated by the computations of the time evolution of a penetrative mixed layer and Rayleigh-Bénard (open-ended, 4:4:1 domain) convection, using 10 × 10 × 100 and 10 × 10 × 20 grids, compared also with finer grids (e.g. 60 × 60 × 100), as well as with one-dimensional treatment using 1 × 1 × 100 and 1 × 1 × 20 nodes. The approach is deemed functional for simulations of a convective boundary layer and mesoscale atmospheric flows, and pollutant transport over realistic complex hilly terrain with heat islands, urban and natural canopies, for diurnal cycles, or subjected to other time and space variations in ground conditions and stratification.

  20. Review of Skin Friction Measurements Including Recent High-Reynolds Number Results from NASA Langley NTF

    NASA Technical Reports Server (NTRS)

    Watson, Ralph D.; Hall, Robert M.; Anders, John B.

    2000-01-01

    This paper reviews flat plate skin friction data from early correlations of drag on plates in water to measurements in the cryogenic environment of The NASA Langley National Transonic Facility (NTF) in late 1996. The flat plate (zero pressure gradient with negligible surface curvature) incompressible skin friction at high Reynolds numbers is emphasized in this paper, due to its importance in assessing the accuracy of measurements, and as being important to the aerodynamics of large scale vehicles. A correlation of zero pressure gradient skin friction data minimizing extraneous effects between tests is often used as the first step in the calculation of skin friction in complex flows. Early data compiled by Schoenherr for a range of momentum thickness Reynolds numbers, R(sub Theta) from 860 to 370,000 contained large scatter, but has proved surprisingly accurate in its correlated form. Subsequent measurements in wind tunnels under more carefully controlled conditions have provided inputs to this database, usually to a maximum R(sub Theta) of about 40,000. Data on a large axisymmetric model in the NASA Langley National Transonic Facility extends the upper limit in incompressible R(sub Theta) to 619,800 using the van Driest transformation. Previous data, test techniques, and error sources ar discussed, and the NTF data will be discussed in detail. The NTF Preston tube and Clauser inferred data accuracy is estimated to be within -2 percent of a power-law curve fit, and falls above the Spalding theory by 1 percent at R(sub Theta) of about 600,000.

  1. Ground Boundary Conditions for Thermal Convection Over Horizontal Surfaces at High Rayleigh Numbers

    NASA Astrophysics Data System (ADS)

    Hanjalić, K.; Hrebtov, M.

    2016-02-01

    We present "wall functions" for treating the ground boundary conditions in the computation of thermal convection over horizontal surfaces at high Rayleigh numbers using coarse numerical grids. The functions are formulated for an algebraic-flux model closed by transport equations for the turbulence kinetic energy, its dissipation rate and scalar variance, but could also be applied to other turbulence models. The three-equation algebraic-flux model, solved in a T-RANS mode ("Transient" Reynolds-averaged Navier-Stokes, based on triple decomposition), was shown earlier to reproduce well a number of generic buoyancy-driven flows over heated surfaces, albeit by integrating equations up to the wall. Here we show that by using a set of wall functions satisfactory results are found for the ensemble-averaged properties even on a very coarse computational grid. This is illustrated by the computations of the time evolution of a penetrative mixed layer and Rayleigh-Bénard (open-ended, 4:4:1 domain) convection, using 10 × 10 × 100 and 10 × 10 × 20 grids, compared also with finer grids (e.g. 60 × 60 × 100 ), as well as with one-dimensional treatment using 1 × 1 × 100 and 1 × 1 × 20 nodes. The approach is deemed functional for simulations of a convective boundary layer and mesoscale atmospheric flows, and pollutant transport over realistic complex hilly terrain with heat islands, urban and natural canopies, for diurnal cycles, or subjected to other time and space variations in ground conditions and stratification.

  2. Numerical aspects in modeling high Deborah number flow and elastic instability

    NASA Astrophysics Data System (ADS)

    Kwon, Youngdon

    2014-05-01

    Investigating highly nonlinear viscoelastic flow in 2D domain, we explore problem as well as property possibly inherent in the streamline upwinding technique (SUPG) and then present various results of elastic instability. The mathematically stable Leonov model written in tensor-logarithmic formulation is employed in the framework of finite element method for spatial discretization of several representative problem domains. For enhancement of computation speed, decoupled integration scheme is applied for shear thinning and Boger-type fluids. From the analysis of 4:1 contraction flow at low and moderate values of the Deborah number (De) the solution with SUPG method does not show noticeable difference from the one by the computation without upwinding. On the other hand, in the flow regime of high De, especially in the state of elastic instability the SUPG significantly distorts the flow field and the result differs considerably from the solution acquired straightforwardly. When the strength of elastic flow and thus the nonlinearity further increase, the computational scheme with upwinding fails to converge and evolutionary solution does not become available any more. All this result suggests that extreme care has to be taken on occasions where upwinding is applied, and one has to first of all prove validity of this algorithm in the case of high nonlinearity. On the contrary, the straightforward computation with no upwinding can efficiently model representative phenomena of elastic instability in such benchmark problems as 4:1 contraction flow, flow over a circular cylinder and flow over asymmetric array of cylinders. Asymmetry of the flow field occurring in the symmetric domain, enhanced spatial and temporal fluctuation of dynamic variables and flow effects caused by extension hardening are properly described in this study.

  3. Experimental Research on Heat Transfer Enhancement for High Prandtl-Number Fluid

    SciTech Connect

    Chiba, Shin-ya; Omae, Masahiro; Yuki, Kazuhisa; Hashizume, Hidetoshi; Toda, Saburo; Sagara, Akio

    2005-04-15

    The experimental research on heat-transfer enhancement for such high Prandtl-number fluid as Flibe has been performed with a large molten salt circulating experimental loop named as 'TNT loop' (Tohoku-NIFS Thermofluid loop). Through the experiments, a packed-bed tube is employed as the enhancer for molten salt. It is clarified that the enhancement of packed-bed tube is superior to that of turbulent heat transfer from the viewpoint of the same flow rate. Also, the 1/4-diameter bed is superior to the 1/2-diameter one at the same flow rate. Furthermore, at low flow rate, a little differences of heat transfer performance can be seen between the stainless-steel bed and copper bed. At high flow rate, however, the heat-transfer coefficient ratio strongly depends on the flow rate in the case of the 1/4-diameter copper bed only. As a result, it is considered that the thermal energy is expanded from a heated wall deeply and fast through packed bed at low flow rate. On the contrary, it is also considered that the convective heat transfer in the vicinity of a heated wall is strong at high flow rate. The evaluation from the viewpoint of the pressure drop shows that the turbulent heat transfer is superior to that with packed bed. However, the ratio of heat transfer with bed to turbulent one is steeply improved at low flow rate. Taking account of MHD effect, avoidance of erosion and electrolysis of Flibe, the enhancement under low flow-rate condition can be suitable in a fusion reactor.

  4. Calibrator Blocks For Computerized Tomography (CT)

    NASA Technical Reports Server (NTRS)

    Engel, H. Peter

    1990-01-01

    Sets of calibrator blocks developed for use with industrial computerized tomography (CT) systems. Set of blocks (or number of stacked sets of blocks) placed on object table of CT system and scanned in usual way. Blocks include holes of known size, shape, and location. Appearance of holes in output image of CT system used to verify operation of system.

  5. Post-Reconstruction Non-Local Means Filtering Methods using CT Side Information for Quantitative SPECT

    PubMed Central

    Chun, Se Young; Fessler, Jeffrey A.; Dewaraja, Yuni K.

    2013-01-01

    Quantitative SPECT techniques are important for many applications including internal emitter therapy dosimetry where accurate estimation of total target activity and activity distribution within targets are both potentially important for dose-response evaluations. We investigated non-local means (NLM) post-reconstruction filtering for accurate I-131 SPECT estimation of both total target activity and the 3D activity distribution. We first investigated activity estimation versus number of ordered-subsets expectation-maximization (OSEM) iterations. We performed simulations using the XCAT phantom with tumors containing a uniform and a non-uniform activity distribution, and measured the recovery coefficient (RC) and the root mean squared error (RMSE) to quantify total target activity and activity distribution, respectively. We observed that using more OSEM iterations is essential for accurate estimation of RC, but may or may not improve RMSE. We then investigated various post-reconstruction filtering methods to suppress noise at high iteration while preserving image details so that both RC and RMSE can be improved. Recently, NLM filtering methods have shown promising results for noise reduction. Moreover, NLM methods using high-quality side information can improve image quality further. We investigated several NLM methods with and without CT side information for I-131 SPECT imaging and compared them to conventional Gaussian filtering and to unfiltered methods. We studied four different ways of incorporating CT information in the NLM methods: two known (NLM CT-B and NLM CT-M) and two newly considered (NLM CT-S and NLM CT-H). We also evaluated the robustness of NLM filtering using CT information to erroneous CT. NLM CT-S and NLM CT-H yielded comparable RC values to unfiltered images while substantially reducing RMSE. NLM CT-S achieved −2.7 to 2.6% increase of RC compared to no filtering and NLM CT-H yielded up to 6% decrease in RC while other methods yielded lower RCs

  6. Post-reconstruction non-local means filtering methods using CT side information for quantitative SPECT

    NASA Astrophysics Data System (ADS)

    Chun, Se Young; Fessler, Jeffrey A.; Dewaraja, Yuni K.

    2013-09-01

    Quantitative SPECT techniques are important for many applications including internal emitter therapy dosimetry where accurate estimation of total target activity and activity distribution within targets are both potentially important for dose-response evaluations. We investigated non-local means (NLM) post-reconstruction filtering for accurate I-131 SPECT estimation of both total target activity and the 3D activity distribution. We first investigated activity estimation versus number of ordered-subsets expectation-maximization (OSEM) iterations. We performed simulations using the XCAT phantom with tumors containing a uniform and a non-uniform activity distribution, and measured the recovery coefficient (RC) and the root mean squared error (RMSE) to quantify total target activity and activity distribution, respectively. We observed that using more OSEM iterations is essential for accurate estimation of RC, but may or may not improve RMSE. We then investigated various post-reconstruction filtering methods to suppress noise at high iteration while preserving image details so that both RC and RMSE can be improved. Recently, NLM filtering methods have shown promising results for noise reduction. Moreover, NLM methods using high-quality side information can improve image quality further. We investigated several NLM methods with and without CT side information for I-131 SPECT imaging and compared them to conventional Gaussian filtering and to unfiltered methods. We studied four different ways of incorporating CT information in the NLM methods: two known (NLM CT-B and NLM CT-M) and two newly considered (NLM CT-S and NLM CT-H). We also evaluated the robustness of NLM filtering using CT information to erroneous CT. NLM CT-S and NLM CT-H yielded comparable RC values to unfiltered images while substantially reducing RMSE. NLM CT-S achieved -2.7 to 2.6% increase of RC compared to no filtering and NLM CT-H yielded up to 6% decrease in RC while other methods yielded lower RCs

  7. 18F-FDG PET of the hands with a dedicated high-resolution PEM system (arthro-PET): correlation with PET/CT, radiography and clinical parameters

    PubMed Central

    Mhlanga, Joyce C.; Carrino, John A.; Lodge, Martin; Wang, Hao

    2015-01-01

    Purpose The aim of this study was to prospectively determine the feasibility and compare the novel use of a positron emission mammography (PEM) scanner with standard PET/CT for evaluating hand osteoarthritis (OA) with 18F-FDG. Methods Institutional review board approval and written informed consent were obtained for this HIPAA-compliant prospective study in which 14 adults referred for oncological 18F-FDG PET/CT underwent dedicated hand PET/CT followed by arthro-PET using the PEM device. Hand radiographs were obtained and scored for the presence and severity of OA. Summed qualitative and quantitative joint glycolytic scores for each modality were compared with the findings on plain radiography and clinical features. Results Eight patients with clinical and/or radiographic evidence of OA comprised the OA group (mean age 73±7.7 years). Six patients served as the control group (53.7±9.3 years). Arthro-PET quantitative and qualitative joint glycolytic scores were highly correlated with PET/CT findings in the OA patients (r=0.86. p =0.007; r=0.94, p=0.001). Qualitative arthro-PET and PET/CT joint scores were significantly higher in the OA patients than in controls (38.7±6.6 vs. 32.2±0.4, p=0.02; 37.5±5.4 vs. 32.2±0.4, p=0.03, respectively). Quantitative arthro-PET and PET/CT maximum SUV-lean joint scores were higher in the OA patients, although they did not reach statistical significance (20.8±4.2 vs. 18±1.8, p= 0.13; 22.8±5.38 vs. 20.1±1.54, p=0.21). By definition, OA patients had higher radiographic joint scores than controls (30.9±31.3 vs. 0, p=0.03). Conclusion Hand imaging using a small field of view PEM system (arthro-PET) with FDG is feasible, performing comparably to PET/CT in assessing metabolic joint activity. Arthro-PET and PET/CT showed higher joint FDG uptake in OA. Further exploration of arthro-PET in arthritis management is warranted. PMID:25134669

  8. MicroCT for comparative morphology: simple staining methods allow high-contrast 3D imaging of diverse non-mineralized animal tissues

    PubMed Central

    Metscher, Brian D

    2009-01-01

    Background Comparative, functional, and developmental studies of animal morphology require accurate visualization of three-dimensional structures, but few widely applicable methods exist for non-destructive whole-volume imaging of animal tissues. Quantitative studies in particular require accurately aligned and calibrated volume images of animal structures. X-ray microtomography (microCT) has the potential to produce quantitative 3D images of small biological samples, but its widespread use for non-mineralized tissues has been limited by the low x-ray contrast of soft tissues. Although osmium staining and a few other techniques have been used for contrast enhancement, generally useful methods for microCT imaging for comparative morphology are still lacking. Results Several very simple and versatile staining methods are presented for microCT imaging of animal soft tissues, along with advice on tissue fixation and sample preparation. The stains, based on inorganic iodine and phosphotungstic acid, are easier to handle and much less toxic than osmium, and they produce high-contrast x-ray images of a wide variety of soft tissues. The breadth of possible applications is illustrated with a few microCT images of model and non-model animals, including volume and section images of vertebrates, embryos, insects, and other invertebrates. Each image dataset contains x-ray absorbance values for every point in the imaged volume, and objects as small as individual muscle fibers and single blood cells can be resolved in their original locations and orientations within the sample. Conclusion With very simple contrast staining, microCT imaging can produce quantitative, high-resolution, high-contrast volume images of animal soft tissues, without destroying the specimens and with possibilities of combining with other preparation and imaging methods. Such images are expected to be useful in comparative, developmental, functional, and quantitative studies of morphology. PMID:19545439

  9. High natural killer cell number might identify stroke patients at risk of developing infections

    PubMed Central

    De Vos, Aurelie; Van Binst, Anne-Marie; De Waele, Marc; Coomans, Danny; Buyl, Ronald; De Keyser, Jacques

    2015-01-01

    Objective: To investigate early changes in leukocyte subsets and autonomic function as predictors of the development of poststroke infections. Methods: We assessed the time course of leukocyte subsets in the blood of 59 patients with acute ischemic stroke. We divided the patients into 2 groups: those who developed infections during the first 7 days after stroke onset and those who did not. We measured urinary norepinephrine and epinephrine concentrations and pulse rate variability indices within 24 hours of admission. Results: We found that the number of circulating natural killer (NK) cells within the first hours after stroke was higher in stroke patients who developed infections (mean 435 cells/mL; 95% confidence interval [CI] 321–588) than in stroke patients who did not develop infections (mean 236 cells/mL; 95% CI 186–300; p = 0.001). This was followed by a decrease in all lymphocyte subsets from admission to day 1, varying between 22% and 40%, which was not seen in patients without poststroke infection (mean increase varied between 2% and 23%; all p < 0.005). In the group that developed infections, pulse rate variability revealed a decreased high frequency component. These findings all remained significant after adjustment for age and stroke volume. Conclusions: High circulating NK cell count within the first hours after ischemic stroke onset followed by a drop in all lymphocyte subsets identified patients who developed infections and may be caused by a sympathovagal imbalance with sympathetic overweight. These findings need to be validated in larger studies. PMID:25738168

  10. Linear global modes in a high Reynolds number Mach 0.9 turbulent jet

    NASA Astrophysics Data System (ADS)

    Schmidt, Oliver; Towne, Aaron; Colonius, Tim

    2015-11-01

    A global linear stability and resolvent analysis of the mean flow from a carefully validated Mach 0 . 9 turbulent jet large eddy simulation (LES) is conducted. Spatiotemporal Fourier decomposition of the simulation data reveals the presence of large scale coherent structures at small azimuthal wavenumbers. The latter wave packets appear as discrete sets of lightly dampened modes in the linear global stability analysis. Their common feature is a spatial separation into an upstream traveling acoustic perturbation in the potential core region, and a Kelvin-Helmholtz-like vortical perturbation which is advected downstream. The least stable branch of discrete modes observed at Strouhal numbers 0 . 38 < St < 0 . 42 exhibits the same acoustic super-directivity as found in the LES and various experimental studies, and hence establishes a direct link between global linear instabilities and low-angle acoustic radiation. Branches at higher frequencies and azimuthal wavenumbers show multi-directive acoustic emission patterns. This observation is of particular interest since high angle, broadband radiation is commonly attributed to stochastic fluctuations of the turbulent jet shear layer.

  11. Flocculation model and collision potential for reactors with flows characterized by high Peclet numbers.

    PubMed

    Weber-Shirk, Monroe L; Lion, Leonard W

    2010-10-01

    A mechanistically-based model is developed to characterize flocculation in the context of flow regimes with high Peclet numbers such as would occur in serpentine flow reactors. These flow conditions are obtained in gravity-driven hydraulic flocculators without mechanical agitation that are an important component of sustainable water treatment systems where energy efficiency and cost are receiving increasing emphasis. The model incorporates a fractal description of flocs, estimates of floc separation distances, estimates of relative velocities of floc particles dependent on the relevant flow regime, and provides an overall prediction of the required reaction time for formation of settleable flocs based on influent turbidity, alum dose, and energy dissipation rate. Viscosity is shown to be significant for the early stage of flocculation and turbulent eddies are shown to be significant for the final stage of flocculation. The collision potential defined as the product of the hydraulic residence time (θ) and the cube root of the energy dissipation rate (ɛ), i.e., ɛ(1/3)θ, is shown to be a better predictor of flocculator performance than the conventional product of θ and the velocity gradient (G), i.e., Gθ. PMID:20605037

  12. A High-Resolution Copy Number Variation Resource for Clinical and Population Genetics

    PubMed Central

    Uddin, Mohammed; Thiruvahindrapuram, Bhooma; Walker, Susan; Wang, Zhuozhi; Hu, Pingzhao; Lamoureux, Sylvia; Wei, John; MacDonald, Jeffrey R.; Pellecchia, Giovanna; Lu, Chao; Lionel, Anath C.; Gazzellone, Matthew J.; McLaughlin, John R.; Brown, Catherine; Andrulis, Irene L.; Knight, Julia A.; Herbrick, Jo-Anne; Wintle, Richard F.; Ray, Peter; Stavropoulos, Dimitri J.; Marshall, Christian R.; Scherer, Stephen W.

    2016-01-01

    Purpose Chromosomal microarray analysis to assess copy number variation (CNV) has become a first tier genetic diagnostic test for individuals with unexplained neurodevelopmental disorders (NDD) or multiple congenital anomalies (MCA). Over 100 cytogenetic labs worldwide use the new ultra-high resolution Affymetrix CytoScan-HD array to genotype hundreds of thousands of samples per year. Our aim was to develop a CNV resource from a new population sample, which would enable more accurate interpretation of clinical genetics data on this microarray platform, and others. Methods Genotyping of 1,000 adult volunteers who are broadly representative of the Ontario population (as obtained from the Ontario Population Genomics Platform) was performed with the CytoScan-HD microarray system, which has 2.7 million probes. Four independent algorithms were applied to detect CNVs. Reproducibility and validation metrics were quantified using sample replicates and quantitative-PCR, respectively. Results DNA from 873 individuals passed quality control and we identified 71,178 CNVs (81 CNVs/individual); 9.8% (6,984) of these CNVs were previously unreported. After applying three layers of filtering criteria, from our highest confidence CNVs dataset we obtained >95% reproducibility and >90% validation rate (73% of these CNVs overlapped at least one gene). Conclusion The genotype data and annotated CNVs for this largely Caucasian population will represent a valuable public resource enabling clinical genetics research and diagnostics. PMID:25503493

  13. The effect of tip speed ratio on a vertical axis wind turbine at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Parker, Colin M.; Leftwich, Megan C.

    2016-05-01

    This work visualizes the flow surrounding a scaled model vertical axis wind turbine at realistic operating conditions. The model closely matches geometric and dynamic properties—tip speed ratio and Reynolds number—of a full-size turbine. The flow is visualized using particle imaging velocimetry (PIV) in the midplane upstream, around, and after (up to 4 turbine diameters downstream) the turbine, as well as a vertical plane behind the turbine. Time-averaged results show an asymmetric wake behind the turbine, regardless of tip speed ratio, with a larger velocity deficit for a higher tip speed ratio. For the higher tip speed ratio, an area of averaged flow reversal is present with a maximum reverse flow of -0.04U_∞. Phase-averaged vorticity fields—achieved by syncing the PIV system with the rotation of the turbine—show distinct structures form from each turbine blade. There were distinct differences in results by tip speed ratios of 0.9, 1.3, and 2.2 of when in the cycle structures are shed into the wake—switching from two pairs to a single pair of vortices being shed—and how they convect into the wake—the middle tip speed ratio vortices convect downstream inside the wake, while the high tip speed ratio pair is shed into the shear layer of the wake. Finally, results show that the wake structure is much more sensitive to changes in tip speed ratio than to changes in Reynolds number.

  14. Using Computational Fluid Dynamics and Experiments to Design Sweeping Jets for High Reynolds Number Cruise Configurations

    NASA Technical Reports Server (NTRS)

    Jones, Gregory S.; Milholen, William E., II; Fell, Jared S.; Webb, Sandy R.; Cagle, C. Mark

    2016-01-01

    The application of a sweeping jet actuator to a circulation control system was initiated by a risk reduction series of experiments to optimize the authority of a single sweeping jet actuator. The sweeping jet design was integrated into the existing Fundamental Aerodynamic Subsonic Transonic- Modular Active Control (FAST-MAC) model by replacing the steady blowing system with an array of thirty-nine sweeping jet cartridges. A constant slot height to wing chord ratio was similar to the steady blowing configuration resulting in each actuator having a unique in size for the sweeping jet configuration. While this paper will describe the scaling and optimization of the actuators for future high Reynolds number applications, the major focus of this effort was to target the transonic flight regime by increasing the amplitude authority of the actuator. This was accomplished by modifying the diffuser of the sweeping jet actuator, and this paper highlights twelve different diffuser designs. The experimental portion of this work was completed in the NASA Langley National Transonic Facility.

  15. Laboratory Study of Homogeneous and Isotropic Turbulence at High Reynolds Number

    NASA Astrophysics Data System (ADS)

    Pecenak, Zachary; Dou, Zhongwang; Yang, Fan; Cao, Lujie; Liang, Zach; Meng, Hui

    2013-11-01

    To study particle dynamics modified by isotropic turbulence at high Reynolds numbers and provide experimental data for DNS validation, we have developed a soccer-ball-shaped truncated icosahedron turbulence chamber with 20 adjoining hexagon surfaces, 12 pentagon surfaces and twenty symettrically displaced fans, which form an enclosed chamber of 1m diameter. We use Particle Image Velocimetry (PIV) technique to characterize the base turbulent flow, using different PIV set ups to capture various characteristic scales of turbulence. Results show that the stationary isotropic turbulence field is a spherical domain with diameter of 40 mm with quasi-zero mean velocities. The maximum rms velocity is ~1.5 m/s, corresponding to a Taylor microscale Re of 450. We extract from the PIV velocity field the whole set of turbulent flow parameters including: turbulent kinetic energy, turbulent intensity, kinetic energy dissipation rate, large eddy length and time scales, the Kolmogorov length, time and velocity scales, Taylor microscale and Re, which are critical to the study of inter-particle statistics modified by turbulence. This research is funded by an NSF grant CBET-0967407.

  16. Magnetic characteristics of a high-layer-number NiFe/FeMn multilayer

    NASA Astrophysics Data System (ADS)

    Paterson, G. W.; Gonçalves, F. J. T.; McFadzean, S.; O'Reilly, S.; Bowman, R.; Stamps, R. L.

    2015-11-01

    We report the static and dynamic magnetic characteristics of a high-layer-number NiFe/FeMn multilayer test structure with potential applications in broadband absorber and filter devices. To allow fine control over the absorption linewidths and to understand the mechanisms governing the resonances in a tailored structure similar to that expected to be used in real world applications, the multilayer was intentionally designed to have layer thickness and interface roughness variations. Magnetometry measurements show that the sample has complex hysteresis loops with features consistent with single ferromagnetic film reversals. Characterisation by transmission electron microscopy allows us to correlate the magnetic properties with structural features, including the film widths and interface roughnesses. Analysis of resonance frequencies from broadband ferromagnetic resonance measurements as a function of field magnitude and orientation provide values of the local exchange bias, rotatable anisotropy, and uniaxial anisotropy fields for specific layers in the stack and explain the observed mode softening. The linewidths of the multilayer are adjustable around the bias field, approaching twice that seen at larger fields, allowing control over the bandwidth of devices formed from the structure.

  17. Critical analysis of high particle number emissions from accelerating compressed natural gas buses.

    PubMed

    Jayaratne, E R; Meyer, N K; Ristovski, Z D; Morawska, L; Miljevic, B

    2010-05-15

    Compressed natural gas (CNG) engines are thought to be less harmful to the environment than conventional diesel engines, especially in terms of particle emissions. Although, this is true with respect to particulate matter (PM) emissions, results of particle number (PN) emission comparisons have been inconclusive. In this study, results of on-road and dynamometer studies of buses were used to derive several important conclusions. We show that, although PN emissions from CNG buses are significantly lower than from diesel buses at low engine power, they become comparable at high power. For diesel buses, PN emissions are not significantly different between acceleration and operation at steady maximum power. However, the corresponding PN emissions from CNG buses when accelerating are an order of magnitude greater than when operating at steady maximum power. During acceleration under heavy load, PN emissions from CNG buses are an order of magnitude higher than from diesel buses. The particles emitted from CNG buses are too small to contribute to PM(10) emissions or contribute to a reduction of visibility and may consist of semivolatile nanoparticles. PMID:20384333

  18. High Rayleigh Number 3-D Spherical Mantle Convection with Radial Basis Functions

    NASA Astrophysics Data System (ADS)

    Flyer, N.; Yuen (3), G. Wright, D.

    2009-04-01

    In the last quarter of a century many numerical methods, such as finite-differences, finite-volume, their yin-yang variants, finite-elements and pseudo-spectral methods have been used to study the problem of 3-D spherical convection. All have their respective strengths but also serious weaknesses, such as low-order and can involve high algorithmic complexity, as in triangular elements. Spectrally accurate methods do not practically allow for local mesh refinement and often involve cumbersome algebra. We have recently introduced a new grid/mesh-free approach, using radial basis functions ( RBFs) . It has the advantage of being spectrally accurate for arbitrary node layouts in multi-dimensions with extreme algorithmic simplicity, and allows naturally node-refinement. One virtue of the RBF scheme is the ability to use a simple Cartesian geometry while implementing the required boundary conditions for the temperature, velocity and stresses on a spherical surface of both the outer( planetary surface ) and inner shell ( core-mantle boundary ). The velocity and stress components are expressed in terms of the scalar potential approach and the other remaining variable is the perturbed temperature field. We have studied the problem from the weakly nonlinear to a moderately nonlinear regime involving a Rayleigh number, about 1000 times super-critical. Both purely basal and partially internal -heating cases have been considered

  19. High Rayleigh Number 3-D Spherical Mantle Convection with Radial Basis Functions

    NASA Astrophysics Data System (ADS)

    Flyer, N.; Wright, G.; Yuen, D. A.

    2009-04-01

    In the last quarter of a century many numerical methods, such as finite-differences, finite-volume, their yin-yang variants, finite-elements and pseudo-spectral methods have been used to study the problem of 3-D spherical convection. All have their respective strengths but also serious weaknesses, such as low-order and can involve high algorithmic complexity, as in triangular elements. Spectrally accurate methods do not practically allow for local mesh refinement and often involve cumbersome algebra. We have recently introduced a new grid/mesh-free approach, using radial basis functions (RBFs). It has the advantage of being spectrally accurate for arbitrary node layouts in multi-dimensions with extreme algorithmic simplicity, and allows naturally node-refinement. One virtue of the RBF scheme is the ability to use a simple Cartesian geometry while implementing the required boundary conditions for the temperature, velocity and stresses on a spherical surface of both the outer(planetary surface) and inner shell (core-mantle boundary). The velocity and stress components are expressed in terms of the scalar potential approach and the other remaining variable is the perturbed temperature field. We have studied the problem from the weakly onlinear to a moderately nonlinear regime involving a Rayleigh number, about 1000 times super-critical. Both purely basal and partially internal-heating cases have been considered.

  20. Dynamic non-equilibrium wall-modeling for large eddy simulation at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Kawai, Soshi; Larsson, Johan

    2013-01-01

    A dynamic non-equilibrium wall-model for large-eddy simulation at arbitrarily high Reynolds numbers is proposed and validated on equilibrium boundary layers and a non-equilibrium shock/boundary-layer interaction problem. The proposed method builds on the prior non-equilibrium wall-models of Balaras et al. [AIAA J. 34, 1111-1119 (1996)], 10.2514/3.13200 and Wang and Moin [Phys. Fluids 14, 2043-2051 (2002)], 10.1063/1.1476668: the failure of these wall-models to accurately predict the skin friction in equilibrium boundary layers is shown and analyzed, and an improved wall-model that solves this issue is proposed. The improvement stems directly from reasoning about how the turbulence length scale changes with wall distance in the inertial sublayer, the grid resolution, and the resolution-characteristics of numerical methods. The proposed model yields accurate resolved turbulence, both in terms of structure and statistics for both the equilibrium and non-equilibrium flows without the use of ad hoc corrections. Crucially, the model accurately predicts the skin friction, something that existing non-equilibrium wall-models fail to do robustly.

  1. Magnetic characteristics of a high-layer-number NiFe/FeMn multilayer

    SciTech Connect

    Paterson, G. W. Gonçalves, F. J. T.; McFadzean, S.; Stamps, R. L.; O'Reilly, S.; Bowman, R.

    2015-11-28

    We report the static and dynamic magnetic characteristics of a high-layer-number NiFe/FeMn multilayer test structure with potential applications in broadband absorber and filter devices. To allow fine control over the absorption linewidths and to understand the mechanisms governing the resonances in a tailored structure similar to that expected to be used in real world applications, the multilayer was intentionally designed to have layer thickness and interface roughness variations. Magnetometry measurements show that the sample has complex hysteresis loops with features consistent with single ferromagnetic film reversals. Characterisation by transmission electron microscopy allows us to correlate the magnetic properties with structural features, including the film widths and interface roughnesses. Analysis of resonance frequencies from broadband ferromagnetic resonance measurements as a function of field magnitude and orientation provide values of the local exchange bias, rotatable anisotropy, and uniaxial anisotropy fields for specific layers in the stack and explain the observed mode softening. The linewidths of the multilayer are adjustable around the bias field, approaching twice that seen at larger fields, allowing control over the bandwidth of devices formed from the structure.

  2. Linear drag law for high-Reynolds-number flow past an oscillating body

    NASA Astrophysics Data System (ADS)

    Agre, Natalie; Childress, Stephen; Zhang, Jun; Ristroph, Leif

    2016-07-01

    An object immersed in a fast flow typically experiences fluid forces that increase with the square of speed. Here we explore how this high-Reynolds-number force-speed relationship is affected by unsteady motions of a body. Experiments on disks that are driven to oscillate while progressing through air reveal two distinct regimes: a conventional quadratic relationship for slow oscillations and an anomalous scaling for fast flapping in which the time-averaged drag increases linearly with flow speed. In the linear regime, flow visualization shows that a pair of counterrotating vortices is shed with each oscillation and a model that views a train of such dipoles as a momentum jet reproduces the linearity. We also show that appropriate scaling variables collapse the experimental data from both regimes and for different oscillatory motions into a single drag-speed relationship. These results could provide insight into the aerodynamic resistance incurred by oscillating wings in flight and they suggest that vibrations can be an effective means to actively control the drag on an object.

  3. High-Throughput Droplet Digital PCR System for Absolute Quantitation of DNA Copy Number

    PubMed Central

    2011-01-01

    Digital PCR enables the absolute quantitation of nucleic acids in a sample. The lack of scalable and practical technologies for digital PCR implementation has hampered the widespread adoption of this inherently powerful technique. Here we describe a high-throughput droplet digital PCR (ddPCR) system that enables processing of ∼2 million PCR reactions using conventional TaqMan assays with a 96-well plate workflow. Three applications demonstrate that the massive partitioning afforded by our ddPCR system provides orders of magnitude more precision and sensitivity than real-time PCR. First, we show the accurate measurement of germline copy number variation. Second, for rare alleles, we show sensitive detection of mutant DNA in a 100 000-fold excess of wildtype background. Third, we demonstrate absolute quantitation of circulating fetal and maternal DNA from cell-free plasma. We anticipate this ddPCR system will allow researchers to explore complex genetic landscapes, discover and validate new disease associations, and define a new era of molecular diagnostics. PMID:22035192

  4. MHC variability supports dog domestication from a large number of wolves: high diversity in Asia

    PubMed Central

    Niskanen, A K; Hagström, E; Lohi, H; Ruokonen, M; Esparza-Salas, R; Aspi, J; Savolainen, P

    2013-01-01

    The process of dog domestication is still somewhat unresolved. Earlier studies indicate that domestic dogs from all over the world have a common origin in Asia. So far, major histocompatibility complex (MHC) diversity has not been studied in detail in Asian dogs, although high levels of genetic diversity are expected at the domestication locality. We sequenced the second exon of the canine MHC gene DLA–DRB1 from 128 Asian dogs and compared our data with a previously published large data set of MHC alleles, mostly from European dogs. Our results show that Asian dogs have a higher MHC diversity than European dogs. We also estimated that there is only a small probability that new alleles have arisen by mutation since domestication. Based on the assumption that all of the currently known 102 DLA–DRB1 alleles come from the founding wolf population, we simulated the number of founding wolf individuals. Our simulations indicate an effective population size of at least 500 founding wolves, suggesting that the founding wolf population was large or that backcrossing has taken place. PMID:23073392

  5. Origin of high particle number concentrations reaching the St. Louis, Midwest Supersite.

    PubMed

    de Foy, Benjamin; Schauer, James J

    2015-08-01

    Ultrafine particles are associated with adverse health effects. Total Particle Number Concentration (TNC) of fine particles were measured during 2002 at the St. Louis - Midwest supersite. The time series showed overall low level with frequent large peaks. The time series was analyzed alongside criteria pollutant measurements and meteorological observations. Multiple regression analysis was used to identify further contributing factors and to determine the association of different pollutants with TNC levels. This showed the strong contribution of sulfur dioxide (SO2) and nitrogen oxides (NOx) to high TNC levels. The analysis also suggested that increased dispersion resulting from faster winds and higher mixing heights led to higher TNC levels. Overall, the results show that there were intense particle nucleation events in a SO2 rich plume reaching the site which contributed around 29% of TNC. A further 40% was associated with primary emissions from mobile sources. By separating the remaining TNC by time of day and clear sky conditions, we suggest that most likely 8% of TNC are due to regional nucleation events and 23% are associated with the general urban background. PMID:26257365

  6. Automated segmentation of the lungs from high resolution CT images for quantitative study of chronic obstructive pulmonary diseases

    NASA Astrophysics Data System (ADS)

    Garg, Ishita; Karwoski, Ronald A.; Camp, Jon J.; Bartholmai, Brian J.; Robb, Richard A.

    2005-04-01

    Chronic obstructive pulmonary diseases (COPD) are debilitating conditions of the lung and are the fourth leading cause of death in the United States. Early diagnosis is critical for timely intervention and effective treatment. The ability to quantify particular imaging features of specific pathology and accurately assess progression or response to treatment with current imaging tools is relatively poor. The goal of this project was to develop automated segmentation techniques that would be clinically useful as computer assisted diagnostic tools for COPD. The lungs were segmented using an optimized segmentation threshold and the trachea was segmented using a fixed threshold characteristic of air. The segmented images were smoothed by a morphological close operation using spherical elements of different sizes. The results were compared to other segmentation approaches using an optimized threshold to segment the trachea. Comparison of the segmentation results from 10 datasets showed that the method of trachea segmentation using a fixed air threshold followed by morphological closing with spherical element of size 23x23x5 yielded the best results. Inclusion of greater number of pulmonary vessels in the lung volume is important for the development of computer assisted diagnostic tools because the physiological changes of COPD can result in quantifiable anatomic changes in pulmonary vessels. Using a fixed threshold to segment the trachea removed airways from the lungs to a better extent as compared to using an optimized threshold. Preliminary measurements gathered from patient"s CT scans suggest that segmented images can be used for accurate analysis of total lung volume and volumes of regional lung parenchyma. Additionally, reproducible segmentation allows for quantification of specific pathologic features, such as lower intensity pixels, which are characteristic of abnormal air spaces in diseases like emphysema.

  7. High-resolution imaging of kidney vascular corrosion casts with Nano-CT.

    PubMed

    Wagner, Roger; Van Loo, Denis; Hossler, Fred; Czymmek, Kirk; Pauwels, Elin; Van Hoorebeke, Luc

    2011-04-01

    A vascular corrosion cast of an entire mouse kidney was scanned with a modular multiresolution X-ray nanotomography system. Using an isotropic voxel pitch of 0.5 μm, capillary systems such as the vasa recta, peritubular capillaries and glomeruli were clearly resolved. This represents a considerable improvement over corrosion casts scanned with microcomputed tomography systems. The resolving power of this system was clearly demonstrated by the unique observation of a dense, subcapsular mat of capillaries enveloping the entire outer surface of the cortical region. Resolution of glomerular capillaries was comparable to similar models derived from laser scanning confocal microscopy. The high-resolution, large field of view and the three-dimensional nature of the resulting data opens new possibilities for the use of corrosion casting in research. PMID:21122193

  8. X-Ray CT of Highly-Attenuating Objects: 9- or 15- MV Spectra?

    SciTech Connect

    Stone, G; Trebes, J; Perry, R; Schneberk, D; Logan, C

    2005-08-29

    We imaged-highly attenuating test objects in three dimensions with 9-MV (at LLNL) and 15-MV (at Hill Air Force Base) x-ray spectra. While we used the same detector and motion control, there were differences that we could not control in the two radiography bays and in the sources. The results show better spatial resolution for the 9-MV spectrum and better contrast for the 15-MV spectrum. The 15-MV data contains a noise pattern that obfuscates the data. It is our judgment that if sufficient attention were given to design of the bay, beam dump, collimation, filtration and linac spot size; a 15-MV imaging system using a flat panel could be developed with spatial resolution of 5 lp/mm and contrastive performance better than we have demonstrated using a 9-MV spectrum.

  9. From high-resolution CT data to finite element models: development of an integrated modular framework.

    PubMed

    Pahr, Dieter H; Zysset, Philippe K

    2009-02-01

    This work introduces a novel method of automating the process of patient-specific finite element (FE) model development using a mapped mesh technique. The objective is to map a predefined mesh (template) of high quality directly onto a new bony surface (target) definition, thereby yielding a similar mesh with minimal user interaction. To bring the template mesh into correspondence with the target surface, a deformable registration technique based on the FE method has been adopted. The procedure has been made hierarchical allowing several levels of mesh refinement to be used, thus reducing the time required to achieve a solution. Our initial efforts have focused on the phalanx bones of the human hand. Mesh quality metrics, such as element volume and distortion were evaluated. Furthermore, the distance between the target surface and the final mapped mesh were measured. The results have satisfactorily proven the applicability of the proposed method. PMID:18839383

  10. Three-dimensional analysis of vesicle and crystal fragment textures in pumice using high-resolution X-ray CT: Textural evidence of eruptive processes

    NASA Astrophysics Data System (ADS)

    Ketcham, R. A.; Gardner, J. E.; Abbott, S.

    2011-12-01

    Three-dimensional analysis of high-resolution X-ray computed tomographic (CT) imagery of pumice from Popocatépetl Volcano in central Mexico yields fresh insights into processes of vesicle formation and coalescence and crystal fragmentation that occur during explosive volcanism. Six ~2 cm pumice fragments of varying bulk vesicularity were imaged at ~20 μm resolution. Three-dimensional blob and fabric analysis quantitatively document textural features, and visualization facilitated contextualization of measurements and overall interpretation. Vesicles range in size from mm-scale to below the resolution of the scan data. By comparing the whole-sample 3D vesicle size distributions derived from CT with more detailed distributions from sub-volumes obtained by standard petrographic analysis, we can discern two distinct, roughly log-normal populations in each sample. Vesicles in all samples have preferred orientations, and fabric analysis based on the star volume distribution and displayed as 3D rose diagrams documents a range of preferred shapes from elongate to flattened. Aspect ratios range from 1 to 6, and converge to values of ~2-3 with increasing size. Surface to volume ratios show increasing departure from sphericity with increasing size, which is probably attributable in large part to irregular shapes caused by coalescence. The vesicle fabric was strongest in the highest-vesicularity sample. Some pumices showed evidence of welding or poor mixing between two or more differently devolatilized portions of melt. Interfaces are in some cases apparently welded, with low-vesicularity glass contact zones, and in others are simply sub-planar intersections between distinct glasses. In one instance of the latter, correlated vesicle and phenocryst orientations across both melt portions and not parallel to their interface suggests that their juxtaposition took place before final eruption, while there was still time for fabric development. The pumices show abundant evidence of

  11. Fibroproliferative changes on high-resolution CT in the acute respiratory distress syndrome predict mortality and ventilator dependency: a prospective observational cohort study

    PubMed Central

    Muranaka, Hiroyuki; Gushima, Yasuhiro; Kotani, Toru; Nader, Habashi M; Fujimoto, Kiminori; Johkoh, Takeshi; Iwamoto, Norihiro; Kawamura, Kodai; Nagano, Junji; Fukuda, Koichiro; Hirata, Naomi; Yoshinaga, Takeshi; Ichiyasu, Hidenori; Tsumura, Shinsuke; Kohrogi, Hirotsugu; Kawaguchi, Atsushi; Yoshioka, Masakazu; Sakuma, Tsutomu; Suga, Moritaka

    2012-01-01

    Objectives To examine whether the extent of fibroproliferative changes on high-resolution CT (HRCT) scan influences prognosis, ventilator dependency and the associated outcomes in patients with early acute respiratory distress syndrome (ARDS). Design A prospective observational cohort study. Setting Intensive care unit in a teaching hospital. Participants 85 patients with ARDS who met American-European Consensus Conference Criteria and eligible criteria. Interventions HRCT scans were performed and prospectively evaluated by two independent observers on the day of diagnosis and graded into six findings according to the extent of fibroproliferation. An overall HRCT score was obtained by previously published method. Primary and secondary outcomes The primary outcome was 60-day mortality. Secondary outcomes included the number of ventilator-free days, organ failure-free days, the incidence of barotraumas and the occurrence of ventilator-associated pneumonia. Results Higher HRCT scores were associated with statistically significant decreases in organ failure-free days as well as ventilator-free days. Multivariate Cox proportional hazards model showed that the HRCT score remained an independent risk factor for mortality (HR 1.20; 95% CI 1.06 to 1.36; p=0.005). Multivariate analysis also revealed that the CT score had predictive value for ventilator weaning within 28 days (OR 0.63; 95% CI 0.48 to 0.82; p=0.0006) as well as for an incidence of barotraumas (OR 1.61; 95% CI 1.08 to 2.38; p=0.018) and for an occurrence of ventilator-associated pneumonia (OR 1.46; 95% CI 1.13 to 1.89; p=0.004). A HRCT score <210 enabled prediction of 60-day survival with 71% sensitivity and 72% specificity and of ventilator-weaning within 28 days with 75% sensitivity and 76% specificity. Conclusions Pulmonary fibroproliferation assessed by HRCT in patients with early ARDS predicts increased mortality with an increased susceptibility to multiple organ failure, including ventilator

  12. Application of a Planar Doppler Velocimetry System to a High Reynolds Number Compressible Jet

    NASA Technical Reports Server (NTRS)

    Smith, Michael W.

    1998-01-01

    A Planar Doppler Velocimetry (PDV) system has been constructed and used to investigate the instantaneous turbulent velocity structure of a round high-speed compressible air jet with a low-speed co-flow. The exit condition was Mach=0.85 at ambient pressure, yielding a Reynolds number of about 650,000 on diameter. The PDV system was installed at NASA Langley Research Center in the Small Anechoic Jet Facility (SAJF), a chamber in which both the acoustic and aerodynamic properties of jets can be studied. For this test, the goal was to gather data which can be used to relate the turbulence structure of the jet to the levels and character of the acoustic noise produced by the jet. The current PDV system can acquire single-velocity-component, single-shot, planar images (15ns exposures) at 30 Hz. For this paper, the primary data set consists of 240 frames of velocity data acquired with both the jet and the low-speed co-flow seeded with light-scattering articles. Thus, velocities could be measured everywhere in the jet shear layer, both in the jet fluid and in the entrained co-flow. Some data were also taken with only the jet flow seeded. These provided mixing concentration images along with the reduced velocity fields. Other images were taken with only the co-flow seeded. These produced unique quantitative images of high speed entrainment. Optical "laser speckle" noise is the largest source of random noise in pulsed PDV systems. Components for the PDV imaging system were specifically selected to minimize speckle noise. To reduce systematic velocity errors due to laser drift, a frequency monitoring reference leg with a temperature-tuned reference iodine cell, was employed. In the course of this study, a novel flow seeder was developed. It enabled continuously variable seeding of the flow with particles of Sheared Pyrogenic Amorphous Hydrophobic Silica (SPAHS). The seeder comprised a dry fluidized bed hopper and a supersonic nozzle "pickup." Shearing action in the pickup

  13. High-Resolution CT and Angiographic Evaluation of NexStent Wall Adaptation

    SciTech Connect

    Nemes, Balazs Lukacs, Levente; Balazs, Gyoergy; Dosa, Edit; Berczi, Viktor; Huettl, Kalman

    2009-05-15

    Carotid stenting is a minimally invasive treatment for extracranial carotid artery stenosis. Stent design may affect technical success and complications in a certain subgroup of patients. We examined the wall adaptability of a new closed-cell carotid stent (NexStent), which has a unique rolled sheet design. Forty-one patients had 42 carotid arteries treated with angioplasty and stenting for internal carotid artery stenosis. The mean patient age was 65 {+-} 10 years. All patients underwent high-resolution computed tomographic angiography after the stent implantation. Data analysis included pre- and postprocedural stenosis, procedure complications, plaque calcification, and stent apposition. We reviewed the angiographic and computed tomographic images for plaque coverage and stent expansion. All procedures were technically successful. Mean stenosis was reduced from 84 {+-} 8% before the procedure to 15.7 {+-} 7% after stenting. Two patients experienced transient ischemic attack; one patient had bradycardia and hypotension. Stent induced kinking was observed in one case. Good plaque coverage and proper overlapping of the rolled sheet was achieved in all cases. There was weak correlation between the residual stenosis and the amount of calcification. The stent provides adequate expansion and adaptation to the tapering anatomy of the bifurcation.

  14. High-accuracy 3D image-based registration of endoscopic video to C-arm cone-beam CT for image-guided skull base surgery

    NASA Astrophysics Data System (ADS)

    Mirota, Daniel J.; Uneri, Ali; Schafer, Sebastian; Nithiananthan, Sajendra; Reh, Douglas D.; Gallia, Gary L.; Taylor, Russell H.; Hager, Gregory D.; Siewerdsen, Jeffrey H.

    2011-03-01

    Registration of endoscopic video to preoperative CT facilitates high-precision surgery of the head, neck, and skull-base. Conventional video-CT registration is limited by the accuracy of the tracker and does not use the underlying video or CT image data. A new image-based video registration method has been developed to overcome the limitations of conventional tracker-based registration. This method adds to a navigation system based on intraoperative C-arm cone-beam CT (CBCT), in turn providing high-accuracy registration of video to the surgical scene. The resulting registration enables visualization of the CBCT and planning data within the endoscopic video. The system incorporates a mobile C-arm, integrated with an optical tracking system, video endoscopy, deformable registration of preoperative CT with intraoperative CBCT, and 3D visualization. Similarly to tracker-based approach, the image-based video-CBCT registration the endoscope is localized with optical tracking system followed by a direct 3D image-based registration of the video to the CBCT. In this way, the system achieves video-CBCT registration that is both fast and accurate. Application in skull-base surgery demonstrates overlay of critical structures (e.g., carotid arteries) and surgical targets with sub-mm accuracy. Phantom and cadaver experiments show consistent improvement of target registration error (TRE) in video overlay over conventional tracker-based registration-e.g., 0.92mm versus 1.82mm for image-based and tracker-based registration, respectively. The proposed method represents a two-fold advance-first, through registration of video to up-to-date intraoperative CBCT, and second, through direct 3D image-based video-CBCT registration, which together provide more confident visualization of target and normal tissues within up-to-date images.

  15. Unsteady pressure measurements on a supercritical airfoil at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Hess, R. W.

    1989-01-01

    Steady and unsteady pressures were measured on a 14 percent supercritical airfoil at transonic Mach numbers at Reynolds numbers from 6,000,000 to 35,000,000. Instrumentation techniques were developed to measure unsteady pressures in a cryogenic tunnel at flight Reynolds numbers. Experimental steady data, corrected for wall effects show very good agreement with calculations from a full potential code with an interacted boundary layer. The steady and unsteady pressures both show a shock position that is dependent on Reynolds number. For a supercritical pressure distribution at a chord Reynolds number of 35,000,000 laminar flow was observed between the leading edge and the shock wave at 45 percent chord.

  16. Pressure recovery performance of conical diffusers at high subsonic Mach numbers

    NASA Technical Reports Server (NTRS)

    Dolan, F. X.; Runstadler, P. W., Jr.

    1973-01-01

    The pressure recovery performance of conical diffusers has been measured for a wide range of geometries and inlet flow conditions. The approximate level and location (in terms of diffuser geometry of optimum performance were determined. Throat Mach numbers from low subsonic (m sub t equals 0.2) through choking (m sub t equals 1.0) were investigated in combination with throat blockage from 0.03 to 0.12. For fixed Mach number, performance was measured over a fourfold range of inlet Reynolds number. Maps of pressure recovery are presented as a function of diffuser geometry for fixed sets of inlet conditions. The influence of inlet blockage, throat Mach number, and inlet Reynolds number is discussed.

  17. Performance evaluation of a sub-millimetre spectrally resolved CT system on high- and low-frequency imaging tasks: a simulation.

    PubMed

    Yveborg, Moa; Danielsson, Mats; Bornefalk, Hans

    2012-04-21

    We are developing a photon-counting silicon strip detector with 0.4 × 0.5 mm² detector elements for clinical CT applications. Except for the limited detection efficiency of approximately 0.8 for a spectrum of 80 kVp, the largest discrepancies from ideal spectral behaviour have been shown to be Compton interactions in the detector and electronic noise. Using the framework of cascaded system analysis, we reconstruct the 3D MTF and NPS of a silicon strip detector including the influence of scatter and charge sharing inside the detector. We compare the reconstructed noise and signal characteristics with a reconstructed 3D MTF and NPS of an ideal energy-integrating detector system with unity detection efficiency, no scatter or charge sharing inside the detector, unity presampling MTF and 1 × 1 mm² detector elements. The comparison is done by calculating the dose-normalized detectability index for some clinically relevant imaging tasks and spectra. This work demonstrates that although the detection efficiency of the silicon detector rapidly drops for the acceleration voltages encountered in clinical computed tomography practice, and despite the high fraction of Compton interactions due to the low atomic number, silicon detectors can perform on a par with ideal energy-integrating detectors for routine imaging tasks containing low-frequency components. For imaging tasks containing high-frequency components, the proposed silicon detector system can perform approximately 1.1-1.3 times better than a fully ideal energy-integrating system. PMID:22469924

  18. Measurements of fluctuating pressure in a rectangular cavity in transonic flow at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Tracy, M. B.; Plentovich, E. B.; Chu, Julio

    1992-01-01

    An experiment was performed in the Langley 0.3 meter Transonic Cryogenic Tunnel to study the internal acoustic field generated by rectangular cavities in transonic and subsonic flows and to determine the effect of Reynolds number and angle of yaw on the field. The cavity was 11.25 in. long and 2.50 in. wide. The cavity depth was varied to obtain length-to-height (l/h) ratios of 4.40, 6.70, 12.67, and 20.00. Data were obtained for a free stream Mach number range from 0.20 to 0.90, a Reynolds number range from 2 x 10(exp 6) to 100 x 10(exp 6) per foot with a nearly constant boundary layer thickness, and for two angles of yaw of 0 and 15 degs. Results show that Reynolds number has little effect on the acoustic field in rectangular cavities at angle of yaw of 0 deg. Cavities with l/h = 4.40 and 6.70 generated tones at transonic speeds, whereas those with l/h = 20.00 did not. This trend agrees with data obtained previously at supersonic speeds. As Mach number decreased, the amplitude, and bandwidth of the tones changed. No tones appeared for Mach number = 0.20. For a cavity with l/h = 12.67, tones appeared at Mach number = 0.60, indicating a possible change in flow field type. Changes in acoustic spectra with angle of yaw varied with Reynolds number, Mach number, l/h ratios, and acoustic mode number.

  19. Image quality in low-dose coronary computed tomography angiography with a new high-definition CT scanner.

    PubMed

    Kazakauskaite, Egle; Husmann, Lars; Stehli, Julia; Fuchs, Tobias; Fiechter, Michael; Klaeser, Bernd; Ghadri, Jelena R; Gebhard, Catherine; Gaemperli, Oliver; Kaufmann, Philipp A

    2013-02-01

    A new generation of high definition computed tomography (HDCT) 64-slice devices complemented by a new iterative image reconstruction algorithm-adaptive statistical iterative reconstruction, offer substantially higher resolution compared to standard definition CT (SDCT) scanners. As high resolution confers higher noise we have compared image quality and radiation dose of coronary computed tomography angiography (CCTA) from HDCT versus SDCT. Consecutive patients (n = 93) underwent HDCT, and were compared to 93 patients who had previously undergone CCTA with SDCT matched for heart rate (HR), HR variability and body mass index (BMI). Tube voltage and current were adapted to the patient's BMI, using identical protocols in both groups. The image quality of all CCTA scans was evaluated by two independent readers in all coronary segments using a 4-point scale (1, excellent image quality; 2, blurring of the vessel wall; 3, image with artefacts but evaluative; 4, non-evaluative). Effective radiation dose was calculated from DLP multiplied by a conversion factor (0.014 mSv/mGy × cm). The mean image quality score from HDCT versus SDCT was comparable (2.02 ± 0.68 vs. 2.00 ± 0.76). Mean effective radiation dose did not significantly differ between HDCT (1.7 ± 0.6 mSv, range 1.0-3.7 mSv) and SDCT (1.9 ± 0.8 mSv, range 0.8-5.5 mSv; P = n.s.). HDCT scanners allow low-dose 64-slice CCTA scanning with higher resolution than SDCT but maintained image quality and equally low radiation dose. Whether this will translate into higher accuracy of HDCT for CAD detection remains to be evaluated. PMID:22825255

  20. Low-Dose High-Pitch CT Angiography of the Supraaortic Arteries Using Sinogram-Affirmed Iterative Reconstruction

    PubMed Central

    Beitzke, Dietrich; Nolz, Richard; Unterhumer, Sylvia; Plank, Christina; Weber, Michael; Schernthaner, Rüdiger; Schöpf, Veronika; Wolf, Florian; Loewe, Christian

    2014-01-01

    Objective To prospectively evaluate image quality and radiation dose using a low-dose computed tomography angiography protocol and iterative image reconstruction for high-pitch dual-source CT-angiography (DSCTA) of the supraaortic arteries. Material and Methods DSCTA was performed in 42 patients, using either 120 kVp tube voltage, 120 mAS tube current, 2.4 pitch and filtered back projection, or 100 kVp tube voltage, 100 mAs tube current, 3.2 pitch, and sinogram affirmed iterative reconstruction. Measurements of vessel attenuation, of the contrast-to-noise ratio (CNR) and the signal-to-noise ratio (SNR) were performed to objectively evaluate image quality. Two readers evaluated subjective image quality and image noise, using a four-point scale. Effective dose was used to compare the differences in radiation dose. Results Low-dose protocol application showed significantly higher vessel opacification (p = 0.013), and non-significantly higher CNR and SNR values. There was no difference in the subjective image quality and image noise reading between the protocols. Effective dose was significantly lower using the low-dose protocol (1.29±0.21 mSv vs. 2.92±0.72 mSv; p<0.001). Conclusion The combined use of reduced tube voltage, reduced tube current, and iterative reconstruction reduces radiation dose by 55.4% in high-pitch DSCTA of the supraaortic arteries without impairment of image quality. PMID:24919195

  1. On the Formation Mechanisms of Artificially Generated High Reynolds Number Turbulent Boundary Layers

    NASA Astrophysics Data System (ADS)

    Rodríguez-López, Eduardo; Bruce, Paul J. K.; Buxton, Oliver R. H.

    2016-08-01

    We investigate the evolution of an artificially thick turbulent boundary layer generated by two families of small obstacles (divided into uniform and non-uniform wall normal distributions of blockage). One- and two-point velocity measurements using constant temperature anemometry show that the canonical behaviour of a boundary layer is recovered after an adaptation region downstream of the trips presenting 150~% higher momentum thickness (or equivalently, Reynolds number) than the natural case for the same downstream distance (x≈ 3 m). The effect of the degree of immersion of the trips for h/δ ≳ 1 is shown to play a secondary role. The one-point diagnostic quantities used to assess the degree of recovery of the canonical properties are the friction coefficient (representative of the inner motions), the shape factor and wake parameter (representative of the wake regions); they provide a severe test to be applied to artificially generated boundary layers. Simultaneous two-point velocity measurements of both spanwise and wall-normal correlations and the modulation of inner velocity by the outer structures show that there are two different formation mechanisms for the boundary layer. The trips with high aspect ratio and uniform distributed blockage leave the inner motions of the boundary layer relatively undisturbed, which subsequently drive the mixing of the obstacles' wake with the wall-bounded flow (wall-driven). In contrast, the low aspect-ratio trips with non-uniform blockage destroy the inner structures, which are then re-formed further downstream under the influence of the wake of the trips (wake-driven).

  2. On the Formation Mechanisms of Artificially Generated High Reynolds Number Turbulent Boundary Layers

    NASA Astrophysics Data System (ADS)

    Rodríguez-López, Eduardo; Bruce, Paul J. K.; Buxton, Oliver R. H.

    2016-03-01

    We investigate the evolution of an artificially thick turbulent boundary layer generated by two families of small obstacles (divided into uniform and non-uniform wall normal distributions of blockage). One- and two-point velocity measurements using constant temperature anemometry show that the canonical behaviour of a boundary layer is recovered after an adaptation region downstream of the trips presenting 150~% higher momentum thickness (or equivalently, Reynolds number) than the natural case for the same downstream distance (x≈ 3 m). The effect of the degree of immersion of the trips for h/δ ≳ 1 is shown to play a secondary role. The one-point diagnostic quantities used to assess the degree of recovery of the canonical properties are the friction coefficient (representative of the inner motions), the shape factor and wake parameter (representative of the wake regions); they provide a severe test to be applied to artificially generated boundary layers. Simultaneous two-point velocity measurements of both spanwise and wall-normal correlations and the modulation of inner velocity by the outer structures show that there are two different formation mechanisms for the boundary layer. The trips with high aspect ratio and uniform distributed blockage leave the inner motions of the boundary layer relatively undisturbed, which subsequently drive the mixing of the obstacles' wake with the wall-bounded flow (wall-driven). In contrast, the low aspect-ratio trips with non-uniform blockage destroy the inner structures, which are then re-formed further downstream under the influence of the wake of the trips (wake-driven).

  3. Spatial patterning of the neonatal EEG suggests a need for a high number of electrodes.

    PubMed

    Odabaee, Maryam; Freeman, Walter J; Colditz, Paul B; Ramon, Ceon; Vanhatalo, Sampsa

    2013-03-01

    There is an increasing demand for source analysis of neonatal EEG, but currently there is inadequate knowledge about i) the spatial patterning of neonatal scalp EEG and hence ii) the number of electrodes needed to capture neonatal EEG in full spatial detail. This study addresses these issues by using a very high density (2.5mm interelectrode spacing) linear electrode array to assess the spatial power spectrum, by using a high density (64 electrodes) EEG cap to assess the spatial extent of the common oscillatory bouts in the neonatal EEG and by using a neonatal size spherical head model to assess the effects of source depth and skull conductivities on the spatial frequency spectrum. The linear array recordings show that the spatial power spectrum decays rapidly until about 0.5-0.8 cycles per centimeter. The dense array EEG recordings show that the amplitude of oscillatory events decays within 4-6 cm to the level of global background activity, and that the higher frequencies (12-20 Hz) show the most rapid spatial decline in amplitude. Simulation with spherical head model showed that realistic variation in skull conductivity and source depths can both introduce orders of magnitude difference in the spatial frequency of the scalp EEG. Calculation of spatial Nyquist frequencies from the spatial power spectra suggests that an interelectrode distance of about 6-10mm would suffice to capture the full spatial texture of the raw EEG signal at the neonatal scalp without spatial aliasing or under-sampling. The spatial decay of oscillatory events suggests that a full representation of their spatial characteristics requires an interelectrode distance of 10-20mm. The findings show that the conventional way of recording neonatal EEG with about 10 electrodes ignores most spatial EEG content, that increasing the electrode density is necessary to improve neonatal EEG source localization and information extraction, and that prospective source models will need to carefully consider the

  4. An efficient numerical method for solving the time-dependent compressible Navier-Stokes equations at high Reynolds number

    NASA Technical Reports Server (NTRS)

    Maccormack, R. W.

    1976-01-01

    A new numerical method used to drastically reduce the computation time required to solve the Navier-Stokes equations at flight Reynolds numbers is described. The new method makes it possible and practical to calculate many important three-dimensional, high Reynolds number flow fields on computers.

  5. Cardiac Computed Tomography (Multidetector CT, or MDCT)

    MedlinePlus

    ... High Blood Pressure Tools & Resources Stroke More Cardiac Computed Tomography (Multidetector CT, or MDCT) Updated:Sep 3,2015 ... facts MDCT is a very fast type of computed tomography (CT) scan. MDCT creates pictures of the healthy ...

  6. LEBU drag reduction in high Reynolds number boundary layers. [Large Eddy Break-Up

    NASA Technical Reports Server (NTRS)

    Anders, J. B.

    1989-01-01

    Conventional and inverted, outer-layer leading-edge breakup devices (LEBUs) were water tunnel tested on an axisymmetric body over the Re number range from 380,000 to 3.8 million. Test results indicate a sharp degradation of the LEBUs' drag-reduction mechanism with increasing Re number. The most likely result of this degradation is a decoupling of the inner and outer scales at higher Re numbers; due to this decoupling, the breakup of the large structures by outer-layer devices has minimal influence on the near-wall, shear-producing scales. This suggests that smaller devices, closer to the walls, may be required for operation at elevated Re numbers.

  7. Excitable dynamics in high-Lewis number premixed gas combustion at normal and microgravity

    NASA Technical Reports Server (NTRS)

    Pearlman, Howard

    1995-01-01

    Freely-propagating, premixed gas flames in high-Lewis (Le) number, quiescent mixtures are studied experimentally in tubes of various diameter at normal (lg) and microgravity (mu g). A premixture of lean butane and oxygen diluted with helium, argon, neon, nitrogen or a mixture of multiple diluents is examined such that the thermal diffusivity of the mixture (and to a lesser extent, the mass diffusivity of the rate-limiting component) is systematically varied. In effect, different diluents allow variation of the Le without changing the chemistry. The flames are recorded with high speed cinematography and their stability is visually assessed. Different modes of propagation were observed depending on the diameter of the tubes (different conductive heat loss), the composition of the mixture and the g-level. At 1g, four modes of propagation were observed in small and intermediate diameter tubes (large conductive heat loss): (1) steadily propagating flames, (2) radial and longitudinal pulsating flames, (3) 'wavering' flames, and (4) rotating spiral flames. As the diameter of the tube increases, the radial modes become more pronounced while the longitudinal modes systematically disappear. Also, multiple, simultaneous, spatially-separated 'pacemaker' sites are observed in intermediate and large diameter tubes. Each site starts as a small region of high luminosity and develops into a flamelet which assumes the form of one of the fore mentioned modes. These flamelets eventually interact, annihilate each other in their regions of intersection and merge at their newly created free-ends. For very large tubes, radially-propagating wave-trains (believed to be 'trigger waves') are observed. These are analogous to the radial pulsations observed in the smaller diameter tubes. At mu g, three modes of propagation have been observed: (1) steadily propagating flames, (2) radial and longitudinal pulsating flames, and (3) multi-armed, rotating flames. Since the pulsating mode exists at mu

  8. PET/MRI and PET/CT in Lung Lesions and Thoracic Malignancies.

    PubMed

    Flechsig, Paul; Mehndiratta, Amit; Haberkorn, Uwe; Kratochwil, Clemens; Giesel, Frederik L

    2015-07-01

    More than one decade ago, introduction of integrated PET/CT scanners changed oncologic imaging and oncologic patient management profoundly. With these systems, the metabolic information acquired by PET can be anatomically localized even to small structures such as small primary tumors, lymph nodes, and soft tissue masses owing to the high-resolution multidetector CT scanners. This has made PET/CT a most reliable method for tumor detection, characterization, staging, and response monitoring. The importance of an integrated functional and morphologic approach to better understand the biology of oncologic disease and to improve therapy planning is underlined by the increasing number of PET/CT systems worldwide, leading to an increasing number of scientific publications in the field. The paradigmatic indication of integrated PET/CT is staging of patients with lung cancer, as PET/CT allows for precise pretherapeutic staging and also posttreatment restaging according to the TNM criteria. The growing numbers of targeted therapy strategies in the fields of surgery, chemotherapy, and radiation therapy, which are adapted to dedicated tumor stages, require the exact classifications of each patient's tumor stage. In this context, whole-body examinations using integrated (18)F-FDG-PET/CT have been shown to reduce the side effects of futile invasive procedures and reduce additional costly staging procedures. In this review article, the diagnostic and therapeutic effects of PET/CT examinations are highlighted and compared with some competitive techniques such as scintigraphy, MRI, and, where possible, integrated PET/MRI. PMID:26050655

  9. An autostereoscopic display with high resolution and large number of view zones

    NASA Astrophysics Data System (ADS)

    Chen, Wu-Li; Hsu, Wei-Liang; Tsai, Chao-Hsu; Wang, Chy-Lin; Wu, Chang-Shuo; Yang, Jinn-Cherng; Cheng, Shu-Chuan

    2008-02-01

    For a spatial-multiplexed 3D display, trade-off between resolution and number of view-zones are usually unavoidable due to the limited number of pixels on the screen. In this paper, we present a new autostereoscopic system, named as "integrated-screen system," to substantially increase the total number of pixels on the screen, which in turn increase both the resolution and number of view-zones. In the integrated-screen system, a large number of mini-projectors are arrayed and the images are tiled together without seams in between. For displaying 3D images, the lenticular screen with predesigned tilted angle is used for distributing different viewing zones. In order to achieve good performance, we design a brand-new projector with specia