Science.gov

Sample records for inversion recovery stir

  1. Chondral lesions in the patellofemoral joint in MRI: Intra-individual comparison of short-tau inversion recovery sequence (STIR) with 2D multiple-echo data image combination sequence (MEDIC).

    PubMed

    Bodelle, Boris; Luboldt, Wolfgang; Wichmann, Julian L; Fischer, Sebastian; Vogl, Thomas J; Beeres, Martin

    2016-01-01

    To determine the value of the 2D multiple-echo data image combination (MEDIC) sequence relative to the short-tau inversion recovery (STIR) sequence regarding the depiction of chondral lesions in the patellofemoral joint. During a period of 6 month patients with acute pain at the anterior aspect of the knee, joint effusion and suspected chondral lesion defect in the patellofemoral joint underwent MRI including axial MEDIC and STIR imaging. Patients with chondral lesions in the patellofemoral joint on at least one sequence were included. The MEDIC and STIR sequence were quantitatively compared regarding the patella cartilage-to-effusion contrast-to-noise ratio (CNR) and qualitatively regarding the depiction of chondral lesions independently scored by two radiologists on a 3-point scale (1 = not depicted; 2 = blurred depicted; 3 = clearly depicted) using the Wilcoxon-Mann-Whitney-Test. For the analysis of inter-observer agreement the Cohen's Weighted Kappa test was used. 30 of 58 patients (male: female, 21:9; age: 44 ± 12 yrs) revealed cartilage lesions (fissures, n = 5 including fibrillation; gaps, n = 15; delamination, n = 7; osteoarthritis, n = 3) and were included in this study. The STIR-sequence was significantly (p < 0.001) superior to the MEDIC-sequence regarding both, the patella cartilage-to-effusion CNR (mean CNR: 232 ± 61 vs. 40 ± 16) as well as the depiction of chondral lesion (mean score: 2.83 ± 0.4 vs. 1.75 ± 0.7) with substantial inter-observer agreement in the rating of both sequences (κ = 0.76-0.89). For the depiction of chondral lesions in the patellofemoral joint, the axial STIR-sequence should be chosen in preference to the axial MEDIC-sequence.

  2. An Inversion Recovery NMR Kinetics Experiment.

    PubMed

    Williams, Travis J; Kershaw, Allan D; Li, Vincent; Wu, Xinping

    2011-05-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a convenient template with which to acquire inversion recovery data on research samples.

  3. An Inversion Recovery NMR Kinetics Experiment

    PubMed Central

    Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping

    2011-01-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a convenient template with which to acquire inversion recovery data on research samples. PMID:21552343

  4. An Inversion Recovery NMR Kinetics Experiment

    ERIC Educational Resources Information Center

    Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping

    2011-01-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this…

  5. An Inversion Recovery NMR Kinetics Experiment

    ERIC Educational Resources Information Center

    Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping

    2011-01-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this…

  6. Evaluation of an integrated continuous stirred microbial electrochemical reactor: Wastewater treatment, energy recovery and microbial community.

    PubMed

    Wang, Haiman; Qu, Youpeng; Li, Da; Zhou, Xiangtong; Feng, Yujie

    2015-11-01

    A continuous stirred microbial electrochemical reactor (CSMER) was developed by integrating anaerobic digestion (AD) and microbial electrochemical system (MES). The system was capable of treating high strength artificial wastewater and simultaneously recovering electric and methane energy. Maximum power density of 583±9, 562±7, 533±10 and 572±6 mW m(-2) were obtained by each cell in a four-independent circuit mode operation at an OLR of 12 kg COD m(-3) d(-1). COD removal and energy recovery efficiency were 87.1% and 32.1%, which were 1.6 and 2.5 times higher than that of a continuous stirred tank reactor (CSTR). Larger amount of Deltaproteobacteria (5.3%) and hydrogenotrophic methanogens (47%) can account for the better performance of CSMER, since syntrophic associations among them provided more degradation pathways compared to the CSTR. Results demonstrate the CSMER holds great promise for efficient wastewater treatment and energy recovery.

  7. Saturation-inversion-recovery: A method for T1 measurement

    NASA Astrophysics Data System (ADS)

    Wang, Hongzhi; Zhao, Ming; Ackerman, Jerome L.; Song, Yiqiao

    2017-01-01

    Spin-lattice relaxation (T1) has always been measured by inversion-recovery (IR), saturation-recovery (SR), or related methods. These existing methods share a common behavior in that the function describing T1 sensitivity is the exponential, e.g., exp(- τ /T1), where τ is the recovery time. In this paper, we describe a saturation-inversion-recovery (SIR) sequence for T1 measurement with considerably sharper T1-dependence than those of the IR and SR sequences, and demonstrate it experimentally. The SIR method could be useful in improving the contrast between regions of differing T1 in T1-weighted MRI.

  8. Inverse problem analysis of pluripotent stem cell aggregation dynamics in stirred-suspension cultures

    PubMed Central

    Rostami, Mahboubeh Rahmati; Wu, Jincheng; Tzanakakis, Emmanuel S.

    2015-01-01

    The cultivation of stem cells as aggregates in scalable bioreactor cultures is an appealing modality for the large-scale manufacturing of stem cell products. Aggregation phenomena are central to such bioprocesses affecting the viability, proliferation and differentiation trajectory of stem cells but a quantitative framework is currently lacking. A population balance equation (PBE) model was used to describe the temporal evolution of the embryonic stem cell (ESC) cluster size distribution by considering collision-induced aggregation and cell proliferation in a stirred-suspension vessel. For ESC cultures at different agitation rates, the aggregation kernel representing the aggregation dynamics was successfully recovered as a solution of the inverse problem. The rate of change of the average aggregate size was greater at the intermediate rate tested suggesting a trade-off between increased collisions and agitation-induced shear. Results from forward simulation with obtained aggregation kernels were in agreement with transient aggregate size data from experiments. We conclude that the framework presented here can complement mechanistic studies offering insights into relevant stem cell clustering processes. More importantly from a process development standpoint, this strategy can be employed in the design and control of bioreactors for the generation of stem cell derivatives for drug screening, tissue engineering and regenerative medicine. PMID:26036699

  9. Double Resonance Inversion Recovery in a Heteronuclear Two Spin System

    NASA Astrophysics Data System (ADS)

    Ishiwata, Mitsumasa; Koizumi, Jun-ichi

    1988-09-01

    For a heteronuclear coupled AX spin system, recovery after inversion of the A spin lines in A-\\{X\\} double resonance spectra is observed under a spin tickling condition. Oscillations in the A lines after inversion are found to decay more rapidly than expected and depend on inhomogeneity of an applied static field. After the initial oscillating stage, the recovery of the tickling spectra can considerably be accelerated by an irradiation field which is applied near a resonance of an X line. A simple mathematical method is presented for calculating the double resonance recovery process under the inhomogeneity of the static field. Such an inhomogeneity modifies a recovery time near the resonance. Experimental results for 13C-enriched formic acid are reproduced by numerical computation. Acceleration of the recovery is explained in terms of a saturation effect of the irradiated line.

  10. Diagnostic accuracy of short-time inversion recovery sequence in Graves' Ophthalmopathy before and after prednisone treatment.

    PubMed

    Tortora, Fabio; Prudente, Mariaevelina; Cirillo, Mario; Elefante, Andrea; Belfiore, Maria Paola; Romano, Francesco; Cappabianca, Salvatore; Carella, Carlo; Cirillo, Sossio

    2014-05-01

    In Graves' Ophthalmopathy, it is important to distinguish active inflammatory phase, responsive to immunosuppressive treatment, from fibrotic unresponsive inactive one. The purpose of this study is, first, to identify the relevant orbital magnetic resonance imaging signal intensities before treatment, so to classify patients according to their clinical activity score (CAS), discriminating inactive (CAS < 3) from active Graves' Ophthalmopathy (GO) (CAS > 3) subjects and, second, to follow post-steroid treatment disease. An observational study was executed on 32 GO consecutive patients in different phases of disease, based on clinical and orbital Magnetic Resonance Imaging parameters, compared to 32 healthy volunteers. Orbital Magnetic Resonance Imaging was performed on a 1.5 tesla Magnetic Resonance Unit by an experienced neuroradiologist blinded to the clinical examinations. In pre-therapy patients, compared to controls, a medial rectus muscle statistically significant signal intensity ratio (SIR) in short-time inversion recovery (STIR) (long TR/TE) sequence was found, as well as when comparing patients before and after treatment, both medial and inferior rectus muscle SIR resulted significantly statistically different in STIR. These increased outcomes explain the inflammation oedematous phase of disease, moreover after steroid administration, compared to controls; patients presented lack of that statistically significant difference, thus suggesting treatment effectiveness. In our study, we proved STIR signal intensities increase in inflammation oedematous phase, confirming STIR sequence to define active phase of disease with more sensibility and reproducibility than CAS alone and to evaluate post-therapy involvement.

  11. Utility of double inversion recovery MRI in paediatric epilepsy

    PubMed Central

    Porter, Samuel G; Saindane, Amit M; Dehkharghani, Seena; Desai, Nilesh K

    2016-01-01

    Detecting focal abnormalities in MRI examinations of children with epilepsy can be a challenging task given the frequently subtle appearance of cortical dysplasia, mesial temporal sclerosis and similar lesions. In this report, we demonstrate the utility of double inversion recovery MRI in the detection of paediatric epileptogenic abnormalities, promoted primarily by increased lesion conspicuity due to complementary suppression of both cerebrospinal fluid and normal white matter signal. PMID:26529229

  12. Inversion Recovery with Embedded Self-Calibration (IRES)

    PubMed Central

    Tan, Ek T.; Riederer, Stephen J.

    2009-01-01

    With self-calibrated parallel acquisition, the calibration data used to characterize coil response are acquired within the actual, parallel scan. Although this eliminates the need for a separate calibration scan, it reduces the net acceleration factor of the parallel scan. Furthermore, this reduction gets worse at higher accelerations. A method is described for 3D inversion recovery gradient-echo imaging in which calibration is incorporated into the sequence but with no loss of net acceleration. This is done by acquiring the calibration data using very small (≤4°) tip angle acquisitions during the delay interval after acquisition of the accelerated imaging data. The technique is studied at 3T with simulation, phantom and in vivo experiments using both image space-based and k-space-based parallel reconstruction methods. At nominal acceleration factors of three and four, the newly described Inversion Recovery with Embedded Self-calibration (IRES) method can retain effective acceleration with comparable SNR and contrast to standard self-calibration. At a net 2D acceleration factor of four, IRES can achieve higher SNR than standard self-calibration having a nominal acceleration factor of six but the same acquisition time. PMID:19365864

  13. Double inversion recovery magnetic resonance imaging of subcortical band heterotopia: a report of 2 cases.

    PubMed

    Zhang, Quan; Zhang, Yunting; Zhang, Jing; Li, Qiong

    2011-01-01

    We report 2 cases of subcortical band heterotopia (SBH) with emphasis on double inversion recovery (DIR) magnetic resonance imaging (MRI). The heterotopic gray matter demonstrated homogeneous high signal intensity and the delineation between the SBH and white matter was distinctly depicted on DIR MRI. Double inversion recovery is a useful adjunct to conventional MRI for the diagnosis of SBH.

  14. Limitations in biexponential fitting of NMR inversion-recovery curves

    NASA Astrophysics Data System (ADS)

    Shazeeb, Mohammed Salman; Sotak, Christopher H.

    2017-03-01

    NMR relaxation agents have long been employed as contrast agents in MRI. In many cases, the contrast agent is confined to either (i) the vascular and/or extracellular compartment (EC), as is the case with gadolinium(III)-based agents, or (ii) the intracellular compartment (IC), as is the case with manganese(II) ions. The compartmentalization of contrast agents often results in tissue-water 1H relaxation profiles that are well modeled as biexponential. It has long been recognized that water exchange between compartments modifies the biexponential relaxation parameters (amplitudes and rate constants) from those that would be found in the absence of exchange. Nevertheless, interpretation in terms of an ;apparent; two-compartment biophysical model, apparent EC vs. apparent IC, can provide insight into tissue structure and function, and changes therein, in the face of physiologic challenge. The accuracy of modeling biexponential data is highly dependent upon the amplitudes, rate constants, and signal-to-noise characterizing the data. Herein, simulated (in silico) inversion-recovery relaxation data are modeled by standard, nonlinear-least-squares analysis and the error in parameter values assessed for a range of amplitudes and rate constants characteristic of in vivo systems following administration of contrast agent. The findings provide guidance for laboratories seeking to exploit contrast-agent-driven, biexponential relaxation to differentiate MRI-based compartmental properties, including the apparent diffusion coefficient.

  15. 3D inversion of full gravity gradient tensor data using SL0 sparse recovery

    NASA Astrophysics Data System (ADS)

    Meng, Zhaohai

    2016-04-01

    We present a new method dedicated to the interpretation of full gravity gradient tensor data, based on SL0 sparse recovery inversion. The SL0 sparse recovery method aims to find out the minimum value of the objective function to fit the data function and to solve the non-zero solution to the objective function. Based on continuous iteration, we can easily obtain the final global minimum (namely the property and space attribute of the inversion target). We consider which type of tensor data combination produces the best inversion results based on the inversion results of different full gravity gradient tensor data combinations (separate tensor data and combined tensor data). We compare the recovered models obtained by inverting the different combinations of different gravity gradient tensor components to understand how different component combinations contribute to the resolution of the recovered model. Based on the comparison between the SL0 sparse recovery inversion results and the smoothest and focusing inversion results of the full gravity gradient tensor data, we show that SL0 sparse recovery inversion can obtain more stable and efficient inversion results with relatively sharp edge information, and that this method can also produce a stable solution of the inverse problem for complex geological structures. This new method to resolve very large full gravity gradient tensor datasets has the considerable advantage of being highly efficient; the full gravity gradient tensor inversion requires very little time. This new method is very effective in explaining the full gravity tensor which is very sensitive to small changes in local anomaly. The numerical simulation and inversion results of the compositional model indicates that including multiple components for inversion increases the resolution of the recovered density model and improves the structure delineation. We apply our inversion method to invert the gravity gradient tensor survey data from the Vinton salt

  16. Magnetic resonance separation imaging using a divided inversion recovery technique (DIRT).

    PubMed

    Goldfarb, James W

    2010-04-01

    The divided inversion recovery technique is an MRI separation method based on tissue T(1) relaxation differences. When tissue T(1) relaxation times are longer than the time between inversion pulses in a segmented inversion recovery pulse sequence, longitudinal magnetization does not pass through the null point. Prior to additional inversion pulses, longitudinal magnetization may have an opposite polarity. Spatial displacement of tissues in inversion recovery balanced steady-state free-precession imaging has been shown to be due to this magnetization phase change resulting from incomplete magnetization recovery. In this paper, it is shown how this phase change can be used to provide image separation. A pulse sequence parameter, the time between inversion pulses (T180), can be adjusted to provide water-fat or fluid separation. Example water-fat and fluid separation images of the head, heart, and abdomen are presented. The water-fat separation performance was investigated by comparing image intensities in short-axis divided inversion recovery technique images of the heart. Fat, blood, and fluid signal was suppressed to the background noise level. Additionally, the separation performance was not affected by main magnetic field inhomogeneities.

  17. Pre- and Postcontrast 3D Double Inversion Recovery Sequence in Multiple Sclerosis: A Simple and Effective MR Imaging Protocol.

    PubMed

    Eichinger, P; Kirschke, J S; Hoshi, M-M; Zimmer, C; Mühlau, M; Riederer, I

    2017-07-27

    The double inversion recovery sequence is known to be very sensitive and specific for MS-related lesions. Our aim was to compare the sensitivity of pre- and postcontrast images of 3D double inversion recovery and conventional 3D T1-weighted images for the detection of contrast-enhancing MS-related lesions in the brain to analyze whether double inversion recovery could be as effective as T1WI. A postcontrast 3D double inversion recovery sequence was acquired in addition to the standard MR imaging protocol at 3T, including pre- and postcontrast 3D T1WI sequences as well as precontrast double inversion recovery of 45 consecutive patients with MS or clinically isolated syndrome between June and December 2013. Two neuroradiologists independently assessed precontrast, postcontrast, and subtraction images of double inversion recovery as well as T1WI to count the number of contrast-enhancing lesions. Afterward, a consensus reading was performed. Lin concordance was calculated between both radiologists, and differences in lesion detectability were assessed with the Student t test. Additionally, the contrast-to-noise ratio was calculated. Significantly more contrast-enhancing lesions could be detected with double inversion recovery compared with T1WI (16%, 214 versus 185, P = .007). The concordance between both radiologists was almost perfect (ρc = 0.94 for T1WI and ρc = 0.98 for double inversion recovery, respectively). The contrast-to-noise ratio was significantly higher in double inversion recovery subtraction images compared with T1-weighted subtraction images (double inversion recovery, 14.3 ± 5.5; T1WI, 6.3 ± 7.1; P < .001). Pre- and postcontrast double inversion recovery enables better detection of contrast-enhancing lesions in MS in the brain compared with T1WI and may be considered an alternative to the standard MR imaging protocol. © 2017 American Society of Neuroradiology.

  18. Flow-independent T(2)-prepared inversion recovery black-blood MR imaging.

    PubMed

    Liu, Chia-Ying; Bley, Thorsten A; Wieben, Oliver; Brittain, Jean H; Reeder, Scott B

    2010-01-01

    To develop a magnetization preparation method to achieve robust, flow-independent blood suppression for cardiac and vascular magnetic resonance imaging (MRI). T(2)Prep-IR sequence consists of a T(2) preparation followed by a nonselective adiabatic inversion pulse. T(2)Prep separates the initial longitudinal magnetization of arterial wall from lumen blood. After the inversion recovery pulse the imaging acquisition is then delayed for a period that allows the blood signal to approach the zero-crossing point. Compared to the conventional double inversion recovery (DIR) preparation, T(2)Prep-IR prepares all the spins regardless of their velocity and direction. T(2)Prep-IR was incorporated into the fast spin echo and fast gradient echo acquisition sequences and images in various planes were acquired in the carotid arteries, thoracic aorta, and heart of normal volunteers. Blood suppression and image quality were compared qualitatively between two different preparations. For in-plane flow carotid images, persistent flow-related artifacts on the DIR images were removed with T(2)Prep-IR. For cardiac applications, T(2)Prep-IR provided robust blood suppression regardless of the flow direction and velocity, including the cardiac long-axis views and the aorta that are often problematic with DIR. T(2)Prep-IR may overcome the flow dependence of DIR by providing robust flow-independent black-blood images. (c) 2009 Wiley-Liss, Inc.

  19. Cross-borehole resistivity inversion: Theory and application to monitoring enhanced oil recovery

    SciTech Connect

    Beasley, C.W.

    1989-01-01

    An algorithm capable of both forward and inverse modeling of cross-borehole resistivity data has been developed. The method of finite elements (FEM) forms the basis of the forward algorithm which computes the secondary electric potential response of a two-dimensional (2-D) earth excited by a three-dimensional (3-D) point source of direct current. The inverse algorithm which is applied to the forward algorithm is an iterative, smoothed least-squares minimization applied to an objective function. As is typical with any 2-D/3-D problem, the governing differential equation for the forward problem is formulated in wavenumber domain via a Fourier transform which removes the effects of the source in the strike direction. The FEM is applied to the transformed equation and potentials in wavenumber domain are computer for a discrete number of transform variables. These potentials are then numerically inverse transformed to obtain potentials in 3-D Cartesian domain. The inverse transform method presented here allows for a cosine transform so that transmitters and receivers are not required to be contained within the plane perpendicular to strike. The inverse program is then used to evaluate the applicability of cross-borehole resistivity inversion to monitoring enhanced oil recovery (EOR) processes. The synthetic model study, which is generic rather than site specific, is directed towards tracking hot water and steam floods. Also included is a discussion of EOR induced rock resistivity variations. The analysis shows that for typical resistivity contrasts associated with EOR processes, repeatedly performing cross-borehole resistivity surveys can be a successful method of tracking EOR fronts.

  20. TIME-LAPSE SEISMIC MODELING & INVERSION OF CO2 SATURATION FOR SEQUESTRATION AND ENHANCED OIL RECOVERY

    SciTech Connect

    Mark A. Meadows

    2006-03-31

    Injection of carbon dioxide (CO2) into subsurface aquifers for geologic storage/sequestration, and into subsurface hydrocarbon reservoirs for enhanced oil recovery, has become an important topic to the nation because of growing concerns related to global warming and energy security. In this project we developed new ways to predict and quantify the effects of CO2 on seismic data recorded over porous reservoir/aquifer rock systems. This effort involved the research and development of new technology to: (1) Quantitatively model the rock physics effects of CO2 injection in porous saline and oil/brine reservoirs (both miscible and immiscible). (2) Quantitatively model the seismic response to CO2 injection (both miscible and immiscible) from well logs (1D). (3) Perform quantitative inversions of time-lapse 4D seismic data to estimate injected CO2 distributions within subsurface reservoirs and aquifers. This work has resulted in an improved ability to remotely monitor the injected CO2 for safe storage and enhanced hydrocarbon recovery, predict the effects of CO2 on time-lapse seismic data, and estimate injected CO2 saturation distributions in subsurface aquifers/reservoirs. We applied our inversion methodology to a 3D time-lapse seismic dataset from the Sleipner CO2 sequestration project, Norwegian North Sea. We measured changes in the seismic amplitude and traveltime at the top of the Sleipner sandstone reservoir and used these time-lapse seismic attributes in the inversion. Maps of CO2 thickness and its standard deviation were generated for the topmost layer. From this information, we estimated that 7.4% of the total CO2 injected over a five-year period had reached the top of the reservoir. This inversion approach could also be applied to the remaining levels within the anomalous zone to obtain an estimate of the total CO2 injected.

  1. Inversions

    ERIC Educational Resources Information Center

    Brown, Malcolm

    2009-01-01

    Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…

  2. Inversions

    ERIC Educational Resources Information Center

    Brown, Malcolm

    2009-01-01

    Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…

  3. Solvent-assisted stir bar sorptive extraction by using swollen polydimethylsiloxane for enhanced recovery of polar solutes in aqueous samples: Application to aroma compounds in beer and pesticides in wine.

    PubMed

    Ochiai, Nobuo; Sasamoto, Kikuo; David, Frank; Sandra, Pat

    2016-07-15

    A novel solvent-assisted stir bar sorptive extraction (SA-SBSE) technique was developed for enhanced recovery of polar solutes in aqueous samples. A conventional PDMS stir bar was swollen in several solvents with log Kow ranging from 1.0 to 3.5 while stirring for 30min prior to extraction. After extraction, thermal desorption - gas chromatography - (tandem) mass spectrometry (TD-GC-(MS/)MS) or liquid desorption - large volume injection (LD-LVI)-GC-MS were performed. An initial study involved investigation of potential solvents for SA-SBSE by weighing of the residual solvent in the swollen PDMS stir bar before and after extraction. Compared to conventional SBSE, SA-SBSE using diethyl ether, methyl isobutyl ketone, dichloromethane, diisopropyl ether and toluene provided higher recoveries from water samples for test solutes with log Kow<2.5. For SA-SBSE using dichloromethane, recoveries were improved by factors of 1.4-4.1, while maintaining or even improving the recoveries for test solutes with log Kow>2.5. The performance of the SA-SBSE method using dichloromethane, diisopropyl ether, and cyclohexane is illustrated with analyses of aroma compounds in beer and of pesticides in wine.

  4. Phase-Sensitive Inversion Recovery for Detecting Myocardial Infarction Using Gadolinium-Delayed Hyperenhancement

    PubMed Central

    Kellman, Peter; Arai, Andrew E.; McVeigh, Elliot R.; Aletras, Anthony H.

    2007-01-01

    After administration of gadolinium, infarcted myocardium exhibits delayed hyperenhancement and can be imaged using an inversion recovery (IR) sequence. The performance of such a method when using magnitude-reconstructed images is highly sensitive to the inversion recovery time (TI) selected. Using phase-sensitive reconstruction, it is possible to use a nominal value of TI, eliminate several breath-holds otherwise needed to find the precise null time for normal myocardium, and achieve a consistent contrast. Phase-sensitive detection is used to remove the background phase while preserving the sign of the desired magnetization during IR. Experimental results are presented which demonstrate the benefits of both phase-sensitive IR image reconstruction and surface coil intensity normalization for detecting myocardial infarction (MI). The phase-sensitive reconstruction method reduces the variation in apparent infarct size that is observed in the magnitude images as TI is changed. Phase-sensitive detection also has the advantage of decreasing the sensitivity to changes in tissue T1 with increasing delay from contrast agent injection. PMID:11810682

  5. Optimization of flow-sensitive alternating inversion recovery (FAIR) for perfusion functional MRI of rodent brain.

    PubMed

    Nasrallah, Fatima A; Lee, Eugene L Q; Chuang, Kai-Hsiang

    2012-11-01

    Arterial spin labeling (ASL) MRI provides a noninvasive method to image perfusion, and has been applied to map neural activation in the brain. Although pulsed labeling methods have been widely used in humans, continuous ASL with a dedicated neck labeling coil is still the preferred method in rodent brain functional MRI (fMRI) to maximize the sensitivity and allow multislice acquisition. However, the additional hardware is not readily available and hence its application is limited. In this study, flow-sensitive alternating inversion recovery (FAIR) pulsed ASL was optimized for fMRI of rat brain. A practical challenge of FAIR is the suboptimal global inversion by the transmit coil of limited dimensions, which results in low effective labeling. By using a large volume transmit coil and proper positioning to optimize the body coverage, the perfusion signal was increased by 38.3% compared with positioning the brain at the isocenter. An additional 53.3% gain in signal was achieved using optimized repetition and inversion times compared with a long TR. Under electrical stimulation to the forepaws, a perfusion activation signal change of 63.7 ± 6.3% can be reliably detected in the primary somatosensory cortices using single slice or multislice echo planar imaging at 9.4 T. This demonstrates the potential of using pulsed ASL for multislice perfusion fMRI in functional and pharmacological applications in rat brain.

  6. Sodium inversion recovery MRI on the knee joint at 7 T with an optimal control pulse

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Seung; Xia, Ding; Madelin, Guillaume; Regatte, Ravinder R.

    2016-01-01

    In the field of sodium magnetic resonance imaging (MRI), inversion recovery (IR) is a convenient and popular method to select sodium in different environments. For the knee joint, IR has been used to suppress the signal from synovial fluids, which improves the correlation between the sodium signal and the concentration of glycosaminoglycans (GAGs) in cartilage tissues. For the better inversion of the magnetization vector under the spatial variations of the B0 and B1 fields, the IR sequence usually employ adiabatic pulses as the inversion pulse. On the other hand, it has been shown that RF shapes robust against the variations of the B0 and B1 fields can be generated by numerical optimization based on optimal control theory. In this work, we compare the performance of fluid-suppressed sodium MRI on the knee joint in vivo, between one implemented with an adiabatic pulse in the IR sequence and the other with the adiabatic pulse replaced by an optimal-control shaped pulse. While the optimal-control pulse reduces the RF power deposited to the body by 58%, the quality of fluid suppression and the signal level of sodium within cartilage are similar between two implementations.

  7. An adaptive joint focal-mechanism inversion method for microseismic data: Application to Aneth CO2 Enhanced Oil Recovery Field

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Chen, T.; Huang, L.

    2016-12-01

    A good azimuthal coverage of geophones is essentially important for focal-mechanism inversion of passive seismic data. However, microseismic monitoring for CO2 injection-induced seisimicity using borehole geophones often suffers from a poor azimuthal coverage of geophones, leading to large uncertainties in inversion. The focal mechanisms of microseismic events occurred within a small region are often similar to one another. We develop an adaptive focal-mechanism inversion method to invert microseismic events with similar focal mechanisms. We first classify microseismic events with similar focal mechanisms into clusters, and then invert the events in a cluster with the same focal mechanism simultaneously. Such inversion strategy is capable of improving convergent rate and reducing inversion uncertainty with abundant data from different azimuths. We develop a new double-difference focal-mechanism inversion method to further improve focal-mechanism inversion by minimizing the residual between observed and synthetic waveforms for pairs of microseismic events at adjacent locations. Our new algorithm allows us to constrain the focal mechanisms among events adjacent to one another. We apply our new adaptive joint focal-mechanism inversion method to microseismic data acquired using a borehole geophone string at a CO2 enhanced oil recovery field in Aneth, Utah. We compare our inversion results with those obtained from inverting focal mechanism for each microseismic event independently, demonstrating that our new inversion method greatly reduce the inversion uncertainty caused by the limited azimuthal coverage of borehole geophones.

  8. Inversion group (IG) fitting: A new T1 mapping method for modified look-locker inversion recovery (MOLLI) that allows arbitrary inversion groupings and rest periods (including no rest period).

    PubMed

    Sussman, Marshall S; Yang, Issac Y; Fok, Kai-Ho; Wintersperger, Bernd J

    2016-06-01

    The Modified Look-Locker Inversion Recovery (MOLLI) technique is used for T1 mapping in the heart. However, a drawback of this technique is that it requires lengthy rest periods in between inversion groupings to allow for complete magnetization recovery. In this work, a new MOLLI fitting algorithm (inversion group [IG] fitting) is presented that allows for arbitrary combinations of inversion groupings and rest periods (including no rest period). Conventional MOLLI algorithms use a three parameter fitting model. In IG fitting, the number of parameters is two plus the number of inversion groupings. This increased number of parameters permits any inversion grouping/rest period combination. Validation was performed through simulation, phantom, and in vivo experiments. IG fitting provided T1 values with less than 1% discrepancy across a range of inversion grouping/rest period combinations. By comparison, conventional three parameter fits exhibited up to 30% discrepancy for some combinations. The one drawback with IG fitting was a loss of precision-approximately 30% worse than the three parameter fits. IG fitting permits arbitrary inversion grouping/rest period combinations (including no rest period). The cost of the algorithm is a loss of precision relative to conventional three parameter fits. Magn Reson Med 75:2332-2340, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  9. Recovery of resources for advanced life support space applications: effect of retention time on biodegradation of two crop residues in a fed-batch, continuous stirred tank reactor

    NASA Technical Reports Server (NTRS)

    Strayer, R. F.; Finger, B. W.; Alazraki, M. P.; Cook, K.; Garland, J. L.

    2002-01-01

    Bioreactor retention time is a key process variable that will influence costs that are relevant to long distance space travel or long duration space habitation. However. little is known about the effects of this parameter on the microbiological treatment options that are being proposed for Advanced Life Support (ALS) systems. Two bioreactor studies were designed to examine this variable. In the first one, six retention times ranging from 1.3 to 21.3 days--were run in duplicate, 81 working-volume continuous stirred tank reactors (CSTR) that were fed ALS wheat residues. Ash-free dry weight loss, carbon mineralization, soluble TOC reduction, changes in fiber content (cellulose, hemicellulose, and lignin), bacterial numbers, and mineral recoveries were monitored. At short retention times--1.33 days--biodegradation was poor (total: 16-20%, cellulose - 12%, hemicellulose - 28%) but soluble TOC was decreased by 75-80% and recovery of major crop inorganic nutrients was adequate, except for phosphorus. A high proportion of the total bacteria (ca. 83%) was actively respiring. At the longest retention time tested, 21.3 days, biodegradation was good (total: 55-60%, cellulose ca. 70%, hemicellulose - ca. 55%) and soluble TOC was decreased by 80%. Recovery of major nutrients, except phosphorus, remained adequate. A very low proportion of total bacteria was actively respiring (ca. 16%). The second bioreactor study used potato residue to determine if even shorter retention times could be used (range 0.25-2.0 days). Although overall biodegradation deteriorated, the degradation of soluble TOC continued to be ca. 75%. We conclude that if the goal of ALS bioprocessing is maximal degradation of crop residues, including cellulose, then retention times of 10 days or longer will be needed. If the goal is to provide inorganic nutrients with the smallest volume/weight bioreactor possible, then a retention time of 1 day (or less) is sufficient.

  10. Recovery of resources for advanced life support space applications: effect of retention time on biodegradation of two crop residues in a fed-batch, continuous stirred tank reactor.

    PubMed

    Strayer, R F; Finger, B W; Alazraki, M P; Cook, K; Garland, J L

    2002-09-01

    Bioreactor retention time is a key process variable that will influence costs that are relevant to long distance space travel or long duration space habitation. However. little is known about the effects of this parameter on the microbiological treatment options that are being proposed for Advanced Life Support (ALS) systems. Two bioreactor studies were designed to examine this variable. In the first one, six retention times ranging from 1.3 to 21.3 days--were run in duplicate, 81 working-volume continuous stirred tank reactors (CSTR) that were fed ALS wheat residues. Ash-free dry weight loss, carbon mineralization, soluble TOC reduction, changes in fiber content (cellulose, hemicellulose, and lignin), bacterial numbers, and mineral recoveries were monitored. At short retention times--1.33 days--biodegradation was poor (total: 16-20%, cellulose - 12%, hemicellulose - 28%) but soluble TOC was decreased by 75-80% and recovery of major crop inorganic nutrients was adequate, except for phosphorus. A high proportion of the total bacteria (ca. 83%) was actively respiring. At the longest retention time tested, 21.3 days, biodegradation was good (total: 55-60%, cellulose ca. 70%, hemicellulose - ca. 55%) and soluble TOC was decreased by 80%. Recovery of major nutrients, except phosphorus, remained adequate. A very low proportion of total bacteria was actively respiring (ca. 16%). The second bioreactor study used potato residue to determine if even shorter retention times could be used (range 0.25-2.0 days). Although overall biodegradation deteriorated, the degradation of soluble TOC continued to be ca. 75%. We conclude that if the goal of ALS bioprocessing is maximal degradation of crop residues, including cellulose, then retention times of 10 days or longer will be needed. If the goal is to provide inorganic nutrients with the smallest volume/weight bioreactor possible, then a retention time of 1 day (or less) is sufficient.

  11. Recovery of resources for advanced life support space applications: effect of retention time on biodegradation of two crop residues in a fed-batch, continuous stirred tank reactor

    NASA Technical Reports Server (NTRS)

    Strayer, R. F.; Finger, B. W.; Alazraki, M. P.; Cook, K.; Garland, J. L.

    2002-01-01

    Bioreactor retention time is a key process variable that will influence costs that are relevant to long distance space travel or long duration space habitation. However. little is known about the effects of this parameter on the microbiological treatment options that are being proposed for Advanced Life Support (ALS) systems. Two bioreactor studies were designed to examine this variable. In the first one, six retention times ranging from 1.3 to 21.3 days--were run in duplicate, 81 working-volume continuous stirred tank reactors (CSTR) that were fed ALS wheat residues. Ash-free dry weight loss, carbon mineralization, soluble TOC reduction, changes in fiber content (cellulose, hemicellulose, and lignin), bacterial numbers, and mineral recoveries were monitored. At short retention times--1.33 days--biodegradation was poor (total: 16-20%, cellulose - 12%, hemicellulose - 28%) but soluble TOC was decreased by 75-80% and recovery of major crop inorganic nutrients was adequate, except for phosphorus. A high proportion of the total bacteria (ca. 83%) was actively respiring. At the longest retention time tested, 21.3 days, biodegradation was good (total: 55-60%, cellulose ca. 70%, hemicellulose - ca. 55%) and soluble TOC was decreased by 80%. Recovery of major nutrients, except phosphorus, remained adequate. A very low proportion of total bacteria was actively respiring (ca. 16%). The second bioreactor study used potato residue to determine if even shorter retention times could be used (range 0.25-2.0 days). Although overall biodegradation deteriorated, the degradation of soluble TOC continued to be ca. 75%. We conclude that if the goal of ALS bioprocessing is maximal degradation of crop residues, including cellulose, then retention times of 10 days or longer will be needed. If the goal is to provide inorganic nutrients with the smallest volume/weight bioreactor possible, then a retention time of 1 day (or less) is sufficient.

  12. Consideration of slice profiles in inversion recovery Look-Locker relaxation parameter mapping.

    PubMed

    Tran-Gia, Johannes; Wech, Tobias; Hahn, Dietbert; Bley, Thorsten A; Köstler, Herbert

    2014-10-01

    To include the flip angle distribution caused by the slice profile into the model used for describing the relaxation curves observed in inversion recovery Look-Locker FLASH T1 mapping for a more accurate determination of the relaxation parameters. For each inversion time, the flip angle dependent signal of the mono-exponential relaxation model is integrated across the slice profile. The resulting Consideration of Slice Profiles (CSP) relaxation curves are compared to the mono-exponential signal model in numerical simulations as well as in phantom and in-vivo experiments. All measured relaxation curves showed systematic deviations from a mono-exponential curve increasing with flip angle and T1 but decreasing with repetition time. Additionally, the accuracy of T1 was found to be largely dependent on the temporal coverage of the relaxation curve. All these systematic errors were largely reduced by the CSP model. The proposed CSP model represents a useful extension of the conventionally used mono-exponential relaxation model. Despite inherent model inaccuracies, the mono-exponential model was found to be sufficient for many T1 mapping situations. However, if only a poor temporal coverage of the relaxation process is achievable or a very precise modeling of the relaxation course is needed as in model-based techniques, the mono-exponential model leads to systematic errors and the CSP model should be used instead. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. Three-dimensional T(1), T(2) and proton density mapping with inversion recovery balanced SSFP.

    PubMed

    Newbould, Rexford D; Skare, Stefan T; Alley, Marcus T; Gold, Garry E; Bammer, Roland

    2010-11-01

    By combining a balanced steady-state free precession (bSSFP) readout with an initial inversion pulse, all three contrast parameters, T(1), T(2) and proton density (M(0)), may be rapidly calculated from the signal progression in time. However, here it is shown that this technique is quite sensitive to variation in the applied transmit RF (B(1)) field, leading to pronounced errors in calculated values. Two-dimensional (2D) acquisitions are taxed to accurately quantify the relaxation, as the short RF pulses required by SSFP's rapid TR contain a broad spectrum of excitation angles. A 3D excitation using a large diameter excitation coil was able to correctly quantify the parameters. While the extreme B(1) sensitivity was previously problematic and has precluded use of IR-bSSFP for relaxometry, in this work these obstacles were significantly reduced, allowing the rapid quantification of T(1), T(2) and M(0). The results may further be used to simulate image contrast from common sequences, such as a T(1)-weighted or fluid-attenuated inversion recovery (FLAIR) examination.

  14. Geoid Recovery Using Geophysical Inverse Theory Applied to Satellite to Satellite Tracking Data

    NASA Technical Reports Server (NTRS)

    Gaposchkin, E. M.

    2000-01-01

    This report describes a new method for determination of the geopotential, or the equivalent geoid. It is based on Satellite-to-Satellite Tracking (SST) of two co-orbiting low earth satellites separated by a few hundred kilometers. The analysis is aimed at the GRACE Mission, though it is generally applicable to any SST data. It is proposed that the SST be viewed as a mapping mission. That is, the result will be maps of the geoid or gravity, as contrasted with determination of spherical harmonics or Fourier coefficients. A method has been developed, based on Geophysical Inverse Theory (GIT), that can provide maps at a prescribed (desired) resolution and the corresponding error map from the SST data. This computation can be done area by area avoiding simultaneous recovery of all the geopotential information. The necessary elements of potential theory, celestial mechanics, and Geophysical Inverse Theory are described, a computation architecture is described, and the results of several simulations presented. Centimeter accuracy geoids with 50 to 100 km resolution can be recovered with a 30 to 60 day mission.

  15. Characterization of myocardial T1-mapping bias caused by intramyocardial fat in inversion recovery and saturation recovery techniques.

    PubMed

    Kellman, Peter; Bandettini, W Patricia; Mancini, Christine; Hammer-Hansen, Sophia; Hansen, Michael S; Arai, Andrew E

    2015-05-10

    Quantitative measurement of T1 in the myocardium may be used to detect both focal and diffuse disease processes such as interstitial fibrosis or edema. A partial volume problem exists when a voxel in the myocardium also contains fat. Partial volume with fat occurs at tissue boundaries or within the myocardium in the case of lipomatous metaplasia of replacement fibrosis, which is commonly seen in chronic myocardial infarction. The presence of fat leads to a bias in T1 measurement. The mechanism for this artifact for widely used T1 mapping protocols using balanced steady state free precession readout and the dependence on off-resonance frequency are described in this paper. Simulations were performed to illustrate the behavior of mono-exponential fitting to bi-exponential mixtures of myocardium and fat with varying fat fractions. Both inversion recovery and saturation recovery imaging protocols using balanced steady state free precession are considered. In-vivo imaging with T1-mapping, water/fat separated imaging, and late enhancement imaging was performed on subjects with chronic myocardial infarction. In n = 17 subjects with chronic myocardial infarction, lipomatous metaplasia is evident in 8 patients (47%). Fat fractions as low as 5% caused approximately 6% T1 elevation for the out-of-phase condition, and approximately 5% reduction of T1 for the in-phase condition. T1 bias in excess of 1000 ms was observed in lipomatous metaplasia with fat fraction of 38% in close agreement with simulation of the specific imaging protocols. Measurement of the myocardial T1 by widely used balanced steady state free precession mapping methods is subject to bias when there is a mixture of water and fat in the myocardium. Intramyocardial fat is frequently present in myocardial scar tissue due lipomatous metaplasia, a process affecting myocardial infarction and some non-ischemic cardiomyopathies. In cases of lipomatous metaplasia, the T1 biases will be additive or subtractive

  16. Sodium inversion recovery MRI of the knee joint in vivo at 7T

    NASA Astrophysics Data System (ADS)

    Madelin, Guillaume; Lee, Jae-Seung; Inati, Souheil; Jerschow, Alexej; Regatte, Ravinder R.

    2010-11-01

    The loss of proteoglycans (PG) in the articular cartilage is an early signature of osteoarthritis (OA). The ensuing changes in the fixed charge density in the cartilage can be directly linked to sodium concentration via charge balance. Sodium ions in the knee joint appear in two pools: in the synovial fluids or joint effusion where the ions are in free motion and bound within the cartilage tissue where the Na+ ions have a restricted motion. The ions in these two compartments have therefore different T1 and T2 relaxation times. The purpose of this study is to demonstrate the feasibility of a fluid-suppressed 3D ultrashort TE radial sodium sequence by implementing an inversion recovery (IR) preparation of the magnetization at 7T. This method could allow a more accurate and more sensitive quantification of loss of PG in patients with OA. It is shown that adiabatic pulses offer significantly improved performance in terms of robustness to B1 and B0 inhomogeneities when compared to the hard pulse sequence. Power deposition considerations further pose a limit to the RF inversion power, and we demonstrate in simulations and experiments how a practical compromise can be struck between clean suppression of fluid signals and power deposition levels. Two IR sequences with different types of inversion pulses (a rectangular pulse and an adiabatic pulse) were tested on a liquid phantom, ex vivo on a human knee cadaver and then in vivo on five healthy volunteers, with a (Nyquist) resolution of ∼3.6 mm and a signal-to-noise ratio of ∼30 in cartilage without IR and ∼20 with IR. Due to specific absorption rate limitations, the total acquisition time was ∼17 min for the 3D radial sequence without inversion or with the rectangular IR, and 24:30 min for the adiabatic IR sequence. It is shown that the adiabatic IR sequence generates a more uniform fluid suppression over the whole sample than the rectangular IR sequence.

  17. Pre- and post-contrast three-dimensional double inversion-recovery MRI in human glioblastoma

    PubMed Central

    Harris, Robert J.; Cloughesy, Timothy F.; Pope, Whitney B.; Godinez, Sergio; Natsuaki, Yutaka; Nghiemphu, Phioanh L.; Meyer, Heiko; Paul, Dominik; Behbahanian, Yalda; Lai, Albert

    2013-01-01

    Fluid attenuated inversion recovery (FLAIR) MRI sequences have become an indispensible tool for defining the malignant boundary in patients with brain tumors by nulling the signal contribution from cerebro-spinal fluid allowing both regions of edema and regions of non-enhancing, infiltrating tumor to become hyperintense on resulting images. In the current study we examined the utility of a three-dimensional double inversion recovery (DIR) sequence that additionally nulls the MR signal associated with white matter, implemented either pre-contrast or post-contrast, in order to determine whether this sequence allows for better differentiation between tumor and normal brain tissue. T1- and T2-weighted, FLAIR, dynamic susceptibility contrast (DSC)-MRI estimates of cerebral blood volume (rCBV), contrast-enhanced T1-weighted images (T1+C), and DIR data (pre- or post-contrast) were acquired in 22 patients with glioblastoma. Contrast-to-noise (CNR) and tumor volumes were compared between DIR and FLAIR sequences. Line profiles across regions of tumor were generated to evaluate similarities between image contrasts. Additionally, voxel-wise associations between DIR and other sequences were examined. Results suggested post-contrast DIR images were hyperintense (bright) in regions spatially similar those having FLAIR hyperintensity and hypointense (dark) in regions with contrast-enhancement or elevated rCBV due to the high sensitivity of 3D turbo spin echo sequences to susceptibility differences between different tissues. DIR tumor volumes were statistically smaller than tumor volumes as defined by FLAIR (Paired t test, P = 0.0084), averaging a difference of approximately 14 mL or 24 %. DIR images had approximately 1.5× higher lesion CNR compared with FLAIR images (Paired t test, P = 0.0048). Line profiles across tumor regions and scatter plots of voxel-wise coherence between different contrasts confirmed a positive correlation between DIR and FLAIR signal intensity and a

  18. Pre- and post-contrast three-dimensional double inversion-recovery MRI in human glioblastoma.

    PubMed

    Harris, Robert J; Cloughesy, Timothy F; Pope, Whitney B; Godinez, Sergio; Natsuaki, Yutaka; Nghiemphu, Phioanh L; Meyer, Heiko; Paul, Dominik; Behbahanian, Yalda; Lai, Albert; Ellingson, Benjamin M

    2013-04-01

    Fluid attenuated inversion recovery (FLAIR) MRI sequences have become an indispensible tool for defining the malignant boundary in patients with brain tumors by nulling the signal contribution from cerebrospinal fluid allowing both regions of edema and regions of non-enhancing, infiltrating tumor to become hyperintense on resulting images. In the current study we examined the utility of a three-dimensional double inversion recovery (DIR) sequence that additionally nulls the MR signal associated with white matter, implemented either pre-contrast or post-contrast, in order to determine whether this sequence allows for better differentiation between tumor and normal brain tissue. T1- and T2-weighted, FLAIR, dynamic susceptibility contrast (DSC)-MRI estimates of cerebral blood volume (rCBV), contrast-enhanced T1-weighted images (T1+C), and DIR data (pre- or post-contrast) were acquired in 22 patients with glioblastoma. Contrast-to-noise (CNR) and tumor volumes were compared between DIR and FLAIR sequences. Line profiles across regions of tumor were generated to evaluate similarities between image contrasts. Additionally, voxel-wise associations between DIR and other sequences were examined. Results suggested post-contrast DIR images were hyperintense (bright) in regions spatially similar those having FLAIR hyperintensity and hypointense (dark) in regions with contrast-enhancement or elevated rCBV due to the high sensitivity of 3D turbo spin echo sequences to susceptibility differences between different tissues. DIR tumor volumes were statistically smaller than tumor volumes as defined by FLAIR (Paired t test, P = 0.0084), averaging a difference of approximately 14 mL or 24 %. DIR images had approximately 1.5× higher lesion CNR compared with FLAIR images (Paired t test, P = 0.0048). Line profiles across tumor regions and scatter plots of voxel-wise coherence between different contrasts confirmed a positive correlation between DIR and FLAIR signal intensity and a

  19. Dual Inversion Recovery Ultrashort Echo Time (DIR UTE) Imaging: Creating High Contrast for Short-T2 Species

    PubMed Central

    Du, Jiang; Takahashi, Atsushi M.; Bae, Won C.; Chung, Christine B.; Bydder, Graeme M.

    2015-01-01

    Imaging of short-T2 species requires not only a short echo time (TE) but also efficient suppression of long-T2 species in order to maximize the short-T2 contrast and dynamic range. This paper introduces a method of long-T2 suppression using two long adiabatic inversion pulses. The first adiabatic inversion pulse inverts the magnetization of long-T2 water and the second one inverts that of fat. Short-T2 species experience a significant transverse relaxation during the long adiabatic inversion process, and are minimally affected by the inversion pulses. Data acquisition with a short TE of 8 μs starts following a time delay of TI1 for the inverted water magnetization to reach a null point, and a time delay of TI2 for the inverted fat magnetization to reach a null point. The suppression of long-T2 species depends on proper combination of TI1, TI2 and TR. It is insensitive to RF inhomogeneities because of the adiabatic inversion pulses. The feasibility of this dual inversion recovery ultrashort TE (DIR UTE) technique was demonstrated on phantoms, cadaveric specimens and healthy volunteers using a clinical 3T scanner. High image contrast was achieved for the deep radial and calcified layers of articular cartilage, cortical bone and the Achilles tendon. PMID:20099332

  20. Evaluation of chondromalacia of the patella with axial inversion recovery-fast spin-echo imaging.

    PubMed

    Lee, S H; Suh, J S; Cho, J; Kim, S J; Kim, S J

    2001-03-01

    The purpose of our study was to assess the accuracy of inversion recovery-fast spin-echo (IR-FSE) imaging for the evaluation of chondromalacia of the patella. Eighty-six patients were included, they underwent magnetic resonance (MR) examination and subsequent knee arthroscopy. Medial and lateral facets of the patella were evaluated separately. Axial images were obtained by using IR-FSE (TR/TE/TI = 3000/25/150 msec; echo train length, 8; 4-mm thickness; 12-cm field of view; 512 x 256 matrix; two, number of excitations) with a 1.5-T MR machine. MR interpretation of chondromalacia was made on the basis of the arthroscopic grading system. Of a total of 172 facets graded, arthroscopy revealed chondromalacia in 14 facets with various grades (G0, 158; G1, 1; G2, 3; G3, 6; G4, 4). Sensitivity, specificity, and accuracy in the chondromalacia grades were 57.1%, 93.0%, and 90.1%, respectively. There was one false-negative case (G4) and 11 false-positive cases (G1, eight; G2, two; G3, one). Sensitivity and specificity corrected by one grade difference were improved to 85.7% and 98.1%, respectively. When cartilage changes were grouped into early (corresponding to grade 1 and 2) and advanced (grade 3 and 4) diseases, sensitivity and specificity of the early and advanced diseases were 75% and 94% and 80% and 99%, respectively. IR-FSE imaging of the knee revealed high specificity but low sensitivity for the evaluation of chondromalacia of the patella.

  1. Pulmonary perfusion quantification with flow-sensitive inversion recovery (FAIR) UTE MRI in small animal imaging.

    PubMed

    Tibiletti, Marta; Bianchi, Andrea; Stiller, Detlef; Rasche, Volker

    2016-12-01

    Blood perfusion in lung parenchyma is an important property for assessing lung function. In small animals, its quantitation is limited even with radioactive isotopes or dynamic contrast-enhanced MRI techniques. In this study, the feasibility flow-sensitive alternating inversion recovery (FAIR) for the quantification of blood flow in lung parenchyma in free breathing rats at 7 T has been investigated. In order to obtain sufficient signal from the short T2 * lung parenchyma, a 2D ultra-short echo time (UTE) Look-Locker read-out has been implemented. Acquisitions were segmented to maintain acquisition time within an acceptable range. A method to perform retrospective respiratory gating (DC-SG) has been applied to investigate the impact of respiratory movement. Reproducibilities within and between sessions were estimated, and the ability of FAIR-UTE to identify the decrease of lung perfusion under hyperoxic conditions was tested. The implemented technique allowed for the visualization of lung parenchyma with excellent SNR and no respiratory artifact even in ungated acquisitions. Lung parenchyma perfusion was obtained as 32.54 ± 2.26 mL/g/min in the left lung, and 34.09 ± 2.75 mL/g/min in the right lung. Application of retrospective gating significantly but minimally changes the perfusion values, implying that respiratory gating may not be necessary with this center-our acquisition method. A decrease of 10% in lung perfusion was found between normoxic and hyperoxic conditions, proving the feasibility of the FAIR-UTE approach to quantify lung perfusion changes. Copyright © 2016 John Wiley & Sons, Ltd.

  2. Fluid-attenuated inversion recovery evolution within 12 hours from stroke onset: a reliable tissue clock?

    PubMed

    Ebinger, Martin; Galinovic, Ivana; Rozanski, Michal; Brunecker, Peter; Endres, Matthias; Fiebach, Jochen B

    2010-02-01

    It has recently been proposed that fluid-attenuated inversion recovery (FLAIR) imaging may serve as a surrogate marker for time of symptom onset after stroke. We assessed the hypothesis that FLAIR imaging could be used to decide if an MRI was performed within 4.5 hours from symptom onset or later. All consecutive patients with presumed stroke who underwent an MRI within 12 hours after known symptom onset were included regardless of stroke subtype and severity between May 2008 and May 2009. Blinded to time of symptom onset, 2 raters judged the visibility of lesions on FLAIR. Apparent diffusion coefficient values, lesion volume on diffusion-weighted imaging, and relative signal intensity of FLAIR lesions were determined. In 94 consecutive patients with stroke, we found that median time from symptom onset for FLAIR-positive patients (189 minutes; interquartile range, 110 to 369 minutes) was significantly longer compared with FLAIR-negative patients (103 minutes; interquartile range, 75 to 183 minutes; P=0.011). Negative FLAIR had a sensitivity of 46% and a specificity of 79% for allocating patients to a time window of less than 4.5 hours. FLAIR positivity increased with diffusion-weighted imaging lesion volume (P<0.001) but showed no correlation with apparent diffusion coefficient values (P=0.795). There was no significant correlation between relative signal intensity and time from symptom onset (Spearman correlation coefficient -0.152, P=0.128). Based on our findings, we cannot recommend the use of FLAIR visibility as an estimate of time from symptom onset within the first 4.5 hours.

  3. Assessment of cardiac function and myocardial morphology using small animal Look-Locker inversion recovery (SALLI) MRI in rats.

    PubMed

    Jeuthe, Sarah; O H-Ici, Darach; Kemnitz, Ulrich; Dietrich, Thore; Schnackenburg, Bernhard; Berger, Felix; Kuehne, Titus; Messroghli, Daniel

    2013-07-19

    Small animal magnetic resonance imaging is an important tool to study cardiac function and changes in myocardial tissue. The high heart rates of small animals (200 to 600 beats/min) have previously limited the role of CMR imaging. Small animal Look-Locker inversion recovery (SALLI) is a T1 mapping sequence for small animals to overcome this problem. T1 maps provide quantitative information about tissue alterations and contrast agent kinetics. It is also possible to detect diffuse myocardial processes such as interstitial fibrosis or edema. Furthermore, from a single set of image data, it is possible to examine heart function and myocardial scarring by generating cine and inversion recovery-prepared late gadolinium enhancement-type MR images. The presented video shows step-by-step the procedures to perform small animal CMR imaging. Here it is presented with a healthy Sprague-Dawley rat, however naturally it can be extended to different cardiac small animal models.

  4. Extraction of energetics from sand using acetone: Acetone extraction of DNT from packed beds and stirred slurries of sand; recovery of acetone for reuse. Final report, 1 May 1995-31 June 1996

    SciTech Connect

    Chase, G.C.; Boggavarapu, R.; Tonangi, S.

    1996-07-31

    A number of military industrial sites for production of energetic compounds (explosives, propellants, and pyrotechnics) have contaminated soils and lagoon sediments. Several methods exist for clean-up of these contaminated soils. The method of solvent extraction is expected to be competitive with the other methods provided that the acetone solvent can be recovered and reused in the process. The amount of solvent required for the separation impacts upon the operation of the extraction processes. The processes generally fall within two extremes: concentrated particle systems (such as in packed beds) or dilute particle systems (such as occur in slurries in stirred tank systems). This report contains the results of experiments conducted on packed bed and stirred tank acetone extraction of sand spiked with 2,4 Di Nitro Toluene (2,4 DNT). The overall economics of the acetone extraction process depends to a large extent on the recovery of the acetone for reuse. The results of this work show that acetone is effective in recovering energetics from sand either in packed beds or stirred tanks. The stirred tank extractor appears to be better than the packed bed extractor requiring less acetone per ton of soil and requiring a shorter contact time. The method that is most promising for recovery of the acetone is that of flashing with a cheap absorbent material such as wood chips to absorb the energetics. The overall cost analysis shows a savings of about $1.2 million per 50 thousand tons of soil washed. This work needs to be extended to clayey type soils and tests conducted on actual lagoon soils.

  5. Myocardial Late Gadolinium Enhancement: Accuracy of T1 Mapping-based Synthetic Inversion-Recovery Imaging.

    PubMed

    Varga-Szemes, Akos; van der Geest, Rob J; Spottiswoode, Bruce S; Suranyi, Pal; Ruzsics, Balazs; De Cecco, Carlo N; Muscogiuri, Giuseppe; Cannaò, Paola M; Fox, Mary A; Wichmann, Julian L; Vliegenthart, Rozemarijn; Schoepf, U Joseph

    2016-02-01

    To compare the accuracy of detection and quantification of myocardial late gadolinium enhancement (LGE) with a synthetic inversion-recovery (IR) approach with that of conventional IR techniques. This prospective study was approved by the institutional review board and compliant with HIPAA. All patients gave written informed consent. Between June and November 2014, 43 patients (25 men; mean age, 54 years ± 16) suspected of having previous myocardial infarction underwent magnetic resonance (MR) imaging, including contrast material-enhanced LGE imaging and T1 mapping. Synthetic magnitude and phase-sensitive IR images were generated on the basis of T1 maps. Images were assessed by two readers. Differences in the per-patient and per-segment LGE detection rates between the synthetic and conventional techniques were analyzed with the McNemar test, and the accuracy of LGE quantification was calculated with the paired t test and Bland-Altman statistics. Interreader agreement for the detection and quantification of LGE was analyzed with κ and Bland-Altman statistics, respectively. Seventeen of the 43 patients (39%) had LGE patterns consistent with myocardial infarction. The sensitivity and specificity of synthetic magnitude and phase-sensitive IR techniques in the detection of LGE were 90% and 95%, respectively, with patient-based analysis and 94% and 99%, respectively, with segment-based analysis. The area of LGE measured with synthetic IR techniques showed excellent agreement with that of conventional techniques (4.35 cm(2) ± 1.88 and 4.14 cm(2)± 1.62 for synthetic magnitude and phase-sensitive IR, respectively, compared with 4.25 cm(2) ± 1.92 and 4.22 cm(2) ± 1.86 for conventional magnitude and phase-sensitive IR, respectively; P > .05). Interreader agreement was excellent for the detection (κ > 0.81) and quantification (bias range, -0.34 to 0.40; P > .05) of LGE. The accuracy of the T1 map-based synthetic IR approach in the detection and quantification of

  6. Validation of net joint loads calculated by inverse dynamics in case of complex movements: application to balance recovery movements.

    PubMed

    Robert, T; Chèze, L; Dumas, R; Verriest, J-P

    2007-01-01

    The joint forces and moments driving the motion of a human subject are classically computed by an inverse dynamic calculation. However, even if this process is theoretically simple, many sources of errors may lead to huge inaccuracies in the results. Moreover, a direct comparison with in vivo measured loads or with "gold standard" values from literature is only possible for very specific studies. Therefore, assessing the inaccuracy of inverse dynamic results is not a trivial problem and a simple method is still required. This paper presents a simple method to evaluate both: (1) the consistency of the results obtained by inverse dynamics; (2) the influence of possible modifications in the inverse dynamic hypotheses. This technique concerns recursive calculation performed on full kinematic chains, and consists in evaluating the loads obtained by two different recursive strategies. It has been applied to complex 3D whole body movements of balance recovery. A recursive Newton-Euler procedure was used to compute the net joint loads. Two models were used to represent the subject bodies, considering or not the upper body as a unique rigid segment. The inertial parameters of the body segments were estimated from two different sets of scaling equations [De Leva, P., 1996. Adjustments to Zatsiorsky-Suleyanov's segment inertia parameters. Journal of Biomechanics 29, 1223-1230; Dumas, R., Chèze, L., Verriest, J.-P., 2006b. Adjustments to McConville et al. and Young et al. Body Segment Inertial Parameters. Journal of Biomechanics, in press]. Using this comparison technique, it has been shown that, for the balance recovery motions investigated: (1) the use of the scaling equations proposed by Dumas et al., instead of those proposed by De Leva, improves the consistency of the results (average relative influence up to 30% for the transversal moment); (2) the arm motions dynamically influence the recovery motion in a non negligible way (average relative influence up to 15% and 30

  7. Adaptive Lp inversion for simultaneous recovery of both blocky and smooth features in a geophysical model

    NASA Astrophysics Data System (ADS)

    Sun, Jiajia; Li, Yaoguo

    2014-05-01

    Minimum-structure inversions using L2-norm measures have been widely applied to geophysical exploration problems. However, the smeared-out models resulting from L2-norm inversions are not always consistent with the real or expected geological structures, especially in regions where distinct interfaces between different rock units exist. To obtain sharp boundaries and blocky features, non-L2 inversions have been used successfully in geophysical imaging problems. In reality, however, both smooth and blocky features can be present in the subsurface physical properties or interfaces to be recovered. To deal with this situation, we develop a new method for adaptively recovering both smooth and blocky features in the constructed model from geophysical inversions. This method first detects different regions of the smoothness or blockiness in a model based on a sequence of inversions and then adaptively applies appropriate Lp model norm with different p values at different locations to complete the final inversion. We present two synthetic examples from basement inversion using gravity data and crosswell seismic traveltime tomography before demonstrating our method on a field data example at the U.S. Geological Survey Fractured Rock Research Site in central New Hampshire.

  8. Effects of Inversion Time on Inversion Recovery Prepared Ultrashort Echo Time (IR-UTE) Imaging of Free and Bound Water in Cortical Bone

    PubMed Central

    Li, Shihong; Ma, Lanqing; Chang, Eric Y; Shao, Hongda; Chen, Jun; Chung, Christine B; Bydder, Graeme M; Du, Jiang

    2014-01-01

    Water is present in cortical bone in different binding states. In this study we aimed to investigate the effects of inversion time (TI) on the signal from bound and pore water in cortical bone using an adiabatic inversion recovery prepared ultrashort echo time (IR-UTE) sequence on a clinical 3T scanner. In total ten bovine midshaft samples and four human tibial midshaft samples were harvested for this study. Each cortical sample was imaged with the UTE and IR-UTE sequences with a TR of 300 ms and a series of TIs ranging from 10 to 240 ms. Five healthy volunteers were also imaged with the same sequence. Single- and bi-component models were utilized to calculate the T2* and relative fractions of short and long T2* components. Bi-component behavior of the signal from cortical bone was seen with the IR-UTE sequence except with a TI of around 80 ms where the short T2* component alone were seen and a mono-exponential decay pattern was observed. In vivo imaging with the IR-UTE sequence provided high contrast-to-noise images with direct visualization of bound water and reduced signal from long T2 muscle and fat. Our preliminary results demonstrate that selective nulling of the pore water component can be achieved with the IR-UTE sequence with an appropriate TI, allowing selective imaging of the bound water component in cortical bone in vivo using clinical MR scanners. PMID:25348196

  9. Does b1000-b0 Mismatch Challenge Diffusion-Weighted Imaging-Fluid Attenuated Inversion Recovery Mismatch in Stroke?

    PubMed

    Geraldo, Ana Filipa; Berner, Lise-Prune; Haesebaert, Julie; Chabrol, Aurélie; Cho, Tae-Hee; Derex, Laurent; Hermier, Marc; Louis-Tisserand, Guy; Chamard, Leila; Klaerke Mikkelsen, Irene; Ribe, Lars; Østergaard, Leif; Hjort, Niels; Pedraza, Salvador; Thomalla, Götz; Baron, Jean-Claude; Nighoghossian, Norbert; Berthèzene, Yves

    2016-03-01

    Our aim was to explore whether the mismatch in lesion visibility between b1000 and b0 images is an alternative to mismatch between diffusion-weighted imaging and fluid-attenuated inversion recovery imaging as a surrogate marker of stroke age. We analyzed patients from the European multicenter I-KNOW database. Independent readers assessed the visibility of ischemic lesions of the anterior circulation on b0 and fluid-attenuated inversion recovery imaging images. The signal-intensity ratio for b0 and fluid-attenuated inversion recovery imaging images was also measured from the segmented stroke lesion volume on b1000 images. This study included 112 patients (68 men; mean age, 67.4 years) with stroke onset within (n=85) or longer than (n=27) 4.5 hours. b1000-b0 mismatch identified patients within 4.5 hours of stroke onset with moderate sensitivity (72.9%; 95% confidence interval [CI], 63.5-82.4) and specificity (70.4%; 95% CI, 53.2-87.6), high positive predictive value (88.6%; 95% CI, 81.1-96.0), and low negative predictive value (45.2%; 95% CI, 30.2-60.3). Global comparison of b1000-b0 mismatch with diffusion-weighted imaging-fluid-attenuated inversion recovery imaging mismatch (considered the imaging gold standard) indicated high sensitivity (85.9%; 95% CI, 78.2-93.6), specificity (91.2%; 95% CI, 76.3-98.1), and positive predictive value (96.7%; 95% CI, 88.0-99.1) and moderate negative predictive value (73.8%; 95% CI, 60.5-87.1) of this new approach. b0 signal-intensity ratio (r=0.251; 95% CI, 0.069-0.417; P=0.008) was significantly although weakly correlated with delay between stroke onset and magnetic resonance imaging. b1000-b0 mismatch may identify patients with ischemic stroke of the within 4.5 hours of onset with high positive predictive value, perhaps constituting an alternative imaging tissue clock. © 2016 American Heart Association, Inc.

  10. Using the dGEMRIC technique to evaluate cartilage health in the presence of surgical hardware at 3T: comparison of inversion recovery and saturation recovery approaches.

    PubMed

    d'Entremont, Agnes G; Kolind, Shannon H; Mädler, Burkhard; Wilson, David R; MacKay, Alexander L

    2014-03-01

    To evaluate the effect of metal artifact reduction techniques on dGEMRIC T(1) calculation with surgical hardware present. We examined the effect of stainless-steel and titanium hardware on dGEMRIC T(1) maps. We tested two strategies to reduce metal artifact in dGEMRIC: (1) saturation recovery (SR) instead of inversion recovery (IR) and (2) applying the metal artifact reduction sequence (MARS), in a gadolinium-doped agarose gel phantom and in vivo with titanium hardware. T(1) maps were obtained using custom curve-fitting software and phantom ROIs were defined to compare conditions (metal, MARS, IR, SR). A large area of artifact appeared in phantom IR images with metal when T(I) ≤ 700 ms. IR maps with metal had additional artifact both in vivo and in the phantom (shifted null points, increased mean T(1) (+151 % IR ROI(artifact)) and decreased mean inversion efficiency (f; 0.45 ROI(artifact), versus 2 for perfect inversion)) compared to the SR maps (ROI(artifact): +13 % T(1) SR, 0.95 versus 1 for perfect excitation), however, SR produced noisier T(1) maps than IR (phantom SNR: 118 SR, 212 IR). MARS subtly reduced the extent of artifact in the phantom (IR and SR). dGEMRIC measurement in the presence of surgical hardware at 3T is possible with appropriately applied strategies. Measurements may work best in the presence of titanium and are severely limited with stainless steel. For regions near hardware where IR produces large artifacts making dGEMRIC analysis impossible, SR-MARS may allow dGEMRIC measurements. The position and size of the IR artifact is variable, and must be assessed for each implant/imaging set-up.

  11. Matched-field processing, geoacoustic inversion, and source signature recovery of blue whale vocalizations.

    PubMed

    Thode, A M; D'Spain, G L; Kuperman, W A

    2000-03-01

    Matched-field processing (MFP) and global inversion techniques have been applied to vocalizations from four whales recorded on a 48-element tilted vertical array off the Channel Islands in 1996. Global inversions from selected whale calls using as few as eight elements extracted information about the surrounding ocean bottom composition, array shape, and the animal's position. These inversion results were then used to conduct straightforward MFP on other calls. The sediment sound-speed inversion estimates are consistent with those derived from sediment samples collected in the area. In general, most animals swam from the east to west, but one animal remained within approximately 500 m of its original position over 45 min. All whales vocalized between 10 and 40 m depth. Three acoustic sequences are discussed in detail: the first illustrating a match between an acoustic track and visual sighting, the second tracking two whales to ranges out to 8 km, and the final sequence demonstrating high-resolution dive profiles from an animal that changed its course to avoid the research platform FLIP (floating instrument platform). This last whale displayed an unusual diversity of signals that include three strong frequency-modulated (FM) downsweeps which contain possible signs of an internal resonance. The arrival of this same whale coincided with a sudden change in oceanographic conditions.

  12. Characterization and optimization of the visualization performance of continuous flow overhauser DNP hyperpolarized water MRI: Inversion recovery approach.

    PubMed

    Terekhov, Maxim; Krummenacker, Jan; Denysenkov, Vasyl; Gerz, Kathrin; Prisner, Thomas; Schreiber, Laura Maria

    2016-03-01

    Overhauser dynamic nuclear polarization (DNP) allows the production of liquid hyperpolarized substrate inside the MRI magnet bore as well as its administration in continuous flow mode to acquire MR images with enhanced signal-to-noise ratio. We implemented inversion recovery preparation in order to improve contrast-to-noise ratio and to quantify the overall imaging performance of Overhauser DNP-enhanced MRI. The negative enhancement created by DNP in combination with inversion recovery (IR) preparation allows canceling selectively the signal originated from Boltzmann magnetization and visualizing only hyperpolarized fluid. The theoretical model describing gain of MR image intensity produced by steady-state continuous flow DNP hyperpolarized magnetization was established and proved experimentally. A precise quantification of signal originated purely from DNP hyperpolarization was achieved. A temperature effect on longitudinal relaxation had to be taken into account to fit experimental results with numerical prediction. Using properly adjusted IR preparation, the complete zeroing of thermal background magnetization was achieved, providing an essential increase of contrast-to-noise ratio of DNP-hyperpolarized water images. To quantify and optimize the steady-state conditions for MRI with continuous flow DNP, an approach similar to that incorporating transient-state thermal magnetization equilibrium in spoiled fast field echo imaging sequences can be used. © 2015 Wiley Periodicals, Inc.

  13. Spectral recovery of outdoor illumination by an extension of the Bayesian inverse approach to the Gaussian mixture model.

    PubMed

    Peyvandi, Shahram; Amirshahi, Seyed Hossein; Hernández-Andrés, Javier; Nieves, Juan Luis; Romero, Javier

    2012-10-01

    The Bayesian inference approach to the inverse problem of spectral signal recovery has been extended to mixtures of Gaussian probability distributions of a training dataset in order to increase the efficiency of estimating the spectral signal from the response of a transformation system. Bayesian (BIC) and Akaike (AIC) information criteria were assessed in order to provide the Gaussian mixture model (GMM) with the optimum number of clusters within the spectral space. The spectra of 2600 solar illuminations measured in Granada (Spain) were recovered over the range of 360-830 nm from their corresponding tristimulus values using a linear model of basis functions, the Wiener inverse (WI) method, and the Bayesian inverse approach extended to the GMM (BGMM). A model of Gaussian mixtures for solar irradiance was deemed to be more appropriate than a single Gaussian distribution for representing the probability distribution of the solar spectral data. The results showed that the estimation performance of the BGMM method was better than either the linear model or the WI method for the spectral approximation of daylight from the three-dimensional tristimulus values.

  14. Atypical appearance of lipomatous tumors on MR images: high signal intensity with fat-suppression STIR sequences.

    PubMed

    Murphy, W D; Hurst, G C; Duerk, J L; Feiglin, D H; Christopher, M; Bellon, E M

    1991-01-01

    Lipomatous tumors generally have signal characteristics that allow them to be diagnosed with great accuracy by means of magnetic resonance imaging. These tumors usually have signal intensities similar to those of subcutaneous fat on both T1- and T2-weighted spin-echo images. Previous reports have not, to the authors' knowledge, described the appearance of lipomatous tumors on images obtained with a short-inversion-time inversion-recovery (STIR) sequence, which can be used to suppress signal from fat. Three lipomatous tumors (two liposarcomas and one lipoma) with signal characteristics unlike those of normal subcutaneous fat at all pulse sequences are presented.

  15. Combined saturation/inversion recovery sequences for improved evaluation of scar and diffuse fibrosis in patients with arrhythmia or heart rate variability.

    PubMed

    Weingärtner, Sebastian; Akçakaya, Mehmet; Basha, Tamer; Kissinger, Kraig V; Goddu, Beth; Berg, Sophie; Manning, Warren J; Nezafat, Reza

    2014-03-01

    To develop arrhythmia-insensitive inversion recovery sequences for improved visualization of myocardial scar and quantification of diffuse fibrosis. A novel preparation pre-pulse, called saturation pulse prepared heart-rate-independent inversion recovery, is introduced, which consists of a combination of saturation and inversion pulses to remove the magnetization history in each heartbeat in late gadolinium enhancement (LGE) imaging and eliminate the need for rest periods in T1 mapping. The proposed LGE and T1 mapping sequences were evaluated against conventional LGE and modified Look-Locker inversion sequences using numerical simulations, phantom and imaging in healthy subjects and patients with suspected or known cardiovascular disease. Simulations and phantom experiments show that the saturation pulse prepared heart-rate-independent inversion recovery pre-pulse in LGE reduces ghosting artifacts and results in perfect nulling of the healthy myocardium in the presence of arrhythmia. In T1 mapping, saturation pulse prepared heart-rate-independent inversion recovery results in (a) reduced scan time (17 vs. 9 heartbeats), (b) insensitivity to heart rate for long T1, and (c) increased signal homogeneity for short T1. LGE images in a patient in atrial fibrillation during the scan show improved myocardial nulling. In vivo T1 maps demonstrate increased signal homogeneity in blood pools and myocardium. The proposed sequences are insensitive to heart rate variability, yield improved LGE images in the presence of arrhythmias, as well as T1 mapping with shorter scan times. Copyright © 2013 Wiley Periodicals, Inc.

  16. Geoid Recovery using Geophysical Inverse Theory Applied to Satellite to Satellite Tracking Data

    NASA Technical Reports Server (NTRS)

    Gaposchkin, E. M.; Frey, H. (Technical Monitor)

    2000-01-01

    This report describes a new method for determination of the geopotential. The analysis is aimed at the GRACE mission. This Satellite-to-Satellite Tracking (SST) mission is viewed as a mapping mission The result will be maps of the geoid. The elements of potential theory, celestial mechanics, and Geophysical Inverse Theory are integrated into a computation architecture, and the results of several simulations presented Centimeter accuracy geoids with 50 to 100 km resolution can be recovered with a 30 to 60 day mission.

  17. TIME-LAPSE MODELING AND INVERSION OF CO2 SATURATION FOR SEQUESTRATION AND ENHANCED OIL RECOVERY

    SciTech Connect

    Mark A. Meadows

    2005-05-25

    In this quarter we have continued our development of the inversion procedure for Phase III, in which time-lapse changes in seismic attributes are inverted to yield changes in CO{sub 2} fluid properties over time. In order to extract seismic attributes from the Sleipner North Sea CO{sub 2} time-lapse data set, a new, detailed interpretation was performed and multiple horizons were picked for the 1994 and 2002 vintages. Traveltime difference maps were constructed at several levels within the Sleipner CO{sub 2} injection zone, and were quantitatively analyzed. No traveltime change was seen in the overburden, as expected, while significant changes were seen in the upper half of the CO{sub 2} injection zone. Evidence of thin-bed tuning and undershooting was also found. A new semi-automated, quantitative method for estimating time sag anomalies was developed, and was used to calculate the amount of time sag along a selected horizon. The resulting time sag estimates matched those seen in the traveltime difference maps. Such a method will be useful for obtaining rapid, accurate quantitative measurements of traveltime changes in the Sleipner data cubes. The traveltime changes will be combined with other attributes, such as amplitude and frequency changes, for input into the real-data inversion.

  18. Importance of Contrast-Enhanced Fluid-Attenuated Inversion Recovery Magnetic Resonance Imaging in Various Intracranial Pathologic Conditions

    PubMed Central

    Lee, Eun Kyoung; Kim, Sungwon; Lee, Yong Seok

    2016-01-01

    Intracranial lesions may show contrast enhancement through various mechanisms that are closely associated with the disease process. The preferred magnetic resonance sequence in contrast imaging is T1-weighted imaging (T1WI) at most institutions. However, lesion enhancement is occasionally inconspicuous on T1WI. Although fluid-attenuated inversion recovery (FLAIR) sequences are commonly considered as T2-weighted imaging with dark cerebrospinal fluid, they also show mild T1-weighted contrast, which is responsible for the contrast enhancement. For several years, FLAIR imaging has been successfully incorporated as a routine sequence at our institution for contrast-enhanced (CE) brain imaging in detecting various intracranial diseases. In this pictorial essay, we describe and illustrate the diagnostic importance of CE-FLAIR imaging in various intracranial pathologic conditions. PMID:26798225

  19. Spinal cord infarction due to fibrocartilaginous embolization: the role of diffusion weighted imaging and short-tau inversion recovery sequences.

    PubMed

    Manara, Renzo; Calderone, Milena; Severino, Maria Savina; Citton, Valentina; Toldo, Irene; Laverda, Anna Maria; Sartori, Stefano

    2010-08-01

    Fibrocartilaginous embolization is a rare cause of ischemic myelopathy caused by embolization of intersomatic disk nucleus pulposus into spinal vasculature during Valsalva-like maneuvers. Diagnostic criteria are based on patient's clinical history, magnetic resonance evidence of T2-hyperintense spinal cord lesion, and exclusion of other causes of ischemic myelopathy. These criteria do not take into account the development of magnetic resonance techniques able to enhance signal abnormalities within the neighboring intersomatic disc or vertebral body and to early characterize central nervous system lesions according to the presence of cytotoxic edema. We present 2 pediatric cases of progressive paraplegia attributed to fibrocartilaginous embolization in which short-tau inversion recovery and diffusion-weighted imaging sequences played a pivotal role showing the ischemic nature of spinal cord lesions. Due to its specificity, diffusion-weighted imaging should be included in the magnetic resonance criteria of fibrocartilaginous embolization and in standard magnetic resonance analysis when dealing with acute transverse myelopathy.

  20. Diagnosis of retrodiscal tissue in painful temporomandibular joint (TMJ) by fluid-attenuated inversion recovery (FLAIR) signal intensity.

    PubMed

    Kuroda, Migiwa; Otonari-Yamamoto, Mika; Sano, Tsukasa; Fujikura, Mamiko; Wakoh, Mamoru

    2015-10-01

    The purpose of the present study is to analyze the fluid-attenuated inversion recovery (FLAIR) signal intensity of the retrodiscal tissue in a painful temporomandibular joint (TMJ), and to develop a diagnostic system based on FLAIR data. The study was based on 33 joints of 17 patients referred for MR imaging of the TMJ. Regions of interest were placed over retrodiscal tissue and gray matter (GM) on FLAIR images. Using signal intensities of GM as reference points, signal intensity ratios (SIR) of retrodiscal tissue were calculated. SIRs in painful TMJ were compared with those in painless TMJ. Wilcoxon's Rank Sum Test was used to analyze the difference in SIRs between the painful and painless groups (P<0·05). The SIRs of retrodiscal tissue were significantly higher in painful joints than in painless joints. FLAIR sequences provide a high signal in patients having painful TMJ, and it suggests that retrodiscal tissue in painful TMJ contains elements such as protein.

  1. A selective inversion recovery method for the improvement of 23Na NMR spectral resolution in isolated perfused rat hearts.

    PubMed

    Simor, T; Kim, S K; Chu, W J; Pohost, G M; Elgavish, G A

    1993-01-01

    Shift-reagent-aided 23Na NMR spectroscopy allows differentiation of the intracellular (Na(i)) and extracellular sodium (Na(o)) signals. The goal of the present study has been to develop a 23Na NMR spectroscopic method to minimize the intensity of the shift-reagent-shifted Na(o) signal and thus increase Na(i) resolution. This is achieved by a selective inversion recovery (SIR) method which enhances the resolution between the Na(i) and Na(o) peaks in shift-reagent-aided 23Na NMR spectroscopy. The application of SIR with Dy(TTHA), Tm(DOTP), or with low concentrations of Dy(PPP)2 results in both good spectral resolution and physiologically acceptable contractile function in the isolated, perfused rat heart model.

  2. Flow-sensitive alternating inversion recovery (fair) imaging for retrograde cortical venous drainage related to intracranial dural arteriovenous fistula.

    PubMed

    Noguchi, Kyo; Kuwayama, Naoya; Kubo, Michiya; Kamisaki, Yuichi; Kameda, Keisuke; Tomizawa, Gakuto; Kawabe, Hideto; Seto, Hikaru

    2011-03-01

    To evaluate the hypothesis that flow-sensitive alternating inversion recovery (FAIR) magnetic resonance (MR) imaging can detect retrograde cortical venous drainage (RCVD) in patients with intracranial dural arteriovenous fistula (DAVF). Seven patients with angiographically confirmed DAVF with RCVD and two DAVF patients without RCVD underwent examinations with conventional MR imaging and FAIR, five of these seven patients with RCVD also underwent examination with dynamic susceptibility contrast (DSC) MR imaging. The ability of FAIR to depict prominent cerebral veins was evaluated, and FAIR was compared with the relative cerebral blood volume (rCBV) maps created with DSC. In all DAVF patients with RCVD, FAIR clearly showed prominent veins on the surface of the brain in affected hemisphere, and FAIR corresponded well with the areas of increased rCBV. In all DAVF patients without RCVD, FAIR showed no prominent veins. FAIR can detect RCVD in patients with DAVF.

  3. Application of (13)C NMR cross-polarization inversion recovery experiments for the analysis of solid dosage forms.

    PubMed

    Pisklak, Dariusz Maciej; Zielińska-Pisklak, Monika; Szeleszczuk, Łukasz

    2016-11-20

    Solid-state nuclear magnetic resonance (ssNMR) is a powerful and unique method for analyzing solid forms of the active pharmaceutical ingredients (APIs) directly in their original formulations. Unfortunately, despite their wide range of application, the ssNMR experiments often suffer from low sensitivity and peaks overlapping between API and excipients. To overcome these limitations, the crosspolarization inversion recovery method was successfully used. The differences in the spin-lattice relaxation time constants for hydrogen atoms T1(H) between API and excipients were employed in order to separate and discriminate their peaks in ssNMR spectra as well as to increase the intensity of API signals in low-dose formulations. The versatility of this method was demonstrated by different examples, including the excipients mixture and commercial solid dosage forms (e.g. granules and tablets). Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Recovery of phenotypes obtained by adaptive evolution through inverse metabolic engineering.

    PubMed

    Hong, Kuk-Ki; Nielsen, Jens

    2012-11-01

    In a previous study, system level analysis of adaptively evolved yeast mutants showing improved galactose utilization revealed relevant mutations. The governing mutations were suggested to be in the Ras/PKA signaling pathway and ergosterol metabolism. Here, site-directed mutants having one of the mutations RAS2(Lys77), RAS2(Tyr112), and ERG5(Pro370) were constructed and evaluated. The mutants were also combined with overexpression of PGM2, earlier proved as a beneficial target for galactose utilization. The constructed strains were analyzed for their gross phenotype, transcriptome and targeted metabolites, and the results were compared to those obtained from reference strains and the evolved strains. The RAS2(Lys77) mutation resulted in the highest specific galactose uptake rate among all of the strains with an increased maximum specific growth rate on galactose. The RAS2(Tyr112) mutation also improved the specific galactose uptake rate and also resulted in many transcriptional changes, including ergosterol metabolism. The ERG5(Pro370) mutation only showed a small improvement, but when it was combined with PGM2 overexpression, the phenotype was almost the same as that of the evolved mutants. Combination of the RAS2 mutations with PGM2 overexpression also led to a complete recovery of the adaptive phenotype in galactose utilization. Recovery of the gross phenotype by the reconstructed mutants was achieved with much fewer changes in the genome and transcriptome than for the evolved mutants. Our study demonstrates how the identification of specific mutations by systems biology can direct new metabolic engineering strategies for improving galactose utilization by yeast.

  5. Dual Inversion Recovery Ultrashort Echo Time (DIR-UTE) Imaging and Quantification of the Zone of Calcified Cartilage (ZCC)

    PubMed Central

    Du, Jiang; Carl, Michael; Bae, Won C.; Statum, Sheronda; Chang, Eric; Bydder, Graeme M; Chung, Christine B.

    2012-01-01

    OBJECTIVE To develop ultrashort echo time (UTE) magnetic resonance imaging (MRI) techniques to image the zone of calcified cartilage (ZCC), and quantify its T2*, T1 and T1ρ. DESIGN In this feasibility study a dual inversion recovery ultrashort echo time (DIR-UTE) sequence was developed for high contrast imaging of the ZCC. T2* of the ZCC was measured with DIR-UTE acquisitions at progressively increasing TEs. T1 of the ZCC was measured with saturation recovery UTE acquisitions at progressively increasing saturation recovery times. T1ρ of the ZCC was measured with spin-locking prepared DIR-UTE acquisitions at progressively increasing spin-locking times. RESULTS The feasibility of the qualitative and quantitative DIR-UTE techniques was demonstrated on phantoms and in six cadaveric patellae using a clinical 3T scanner. On average the ZCC has a short T2* ranging from 1.0 to 3.3 ms (mean ± standard deviation = 2.0 ± 1.2 ms), a short T1 ranging from 256 to 389 ms (mean ± standard deviation = 305 ± 45 ms), and a short T1ρ ranging from 2.2 to 4.6 ms (mean ± standard deviation = 3.6 ± 1.2 ms). CONCLUSION UTE MR based techniques have been developed for high resolution imaging of the ZCC and quantitative evaluation of its T2*, T1 and T1ρ relaxation times, providing noninvasive assessment of collagen orientation and proteoglycan content at the zone of calcified cartilage and the bone cartilage interface. These measurements may be useful for non-invasive assessment of the ZCC, including understanding the involvement of this tissue component in osteoarthritis. PMID:23025927

  6. Three Dimensional T1, T2, and Proton Density Mapping with Inversion Recovery Balanced SSFP

    PubMed Central

    Newbould, Rexford D.; Skare, Stefan T.; Alley, Marcus T.; Gold, Garry E.; Bammer, Roland

    2010-01-01

    By combining a bSSFP readout with an initial inversion pulse, all three contrast parameters, T1, T2, and proton density (M0), may be rapidly calculated from the signal progression in time. However, here it is shown that this technique is quite sensitive to variation in the applied transmit RF (B1) field, leading to pronounced errors in calculated values. 2D acquisitions are taxed to accurately quantify the relaxation, as the short RF pulses required by SSFP's rapid TR contain a broad spectrum of excitation angles. A 3D excitation using a large diameter excitation coil was able to correctly quantify the parameters. While the extreme B1 sensitivity was previously problematic, and has precluded use of IR-bSSFP for relaxometry, in this work these obstacles were significantly reduced, allowing the rapid quantification of T1, T2, and M0. The results may further be used to simulate image contrast from common sequences, such as a T1-weighted or FLAIR examination. PMID:20692784

  7. Ultrasonic Stir Welding

    NASA Technical Reports Server (NTRS)

    Nabors, Sammy

    2015-01-01

    NASA Marshall Space Flight Center (MSFC) developed Ultrasonic Stir Welding (USW) to join large pieces of very high-strength metals such as titanium and Inconel. USW, a solid-state weld process, improves current thermal stir welding processes by adding high-power ultrasonic (HPU) energy at 20 kHz frequency. The addition of ultrasonic energy significantly reduces axial, frictional, and shear forces; increases travel rates; and reduces wear on the stir rod, which results in extended stir rod life. The USW process decouples the heating, stirring, and forging elements found in the friction stir welding process allowing for independent control of each process element and, ultimately, greater process control and repeatability. Because of the independent control of USW process elements, closed-loop temperature control can be integrated into the system so that a constant weld nugget temperature can be maintained during welding.

  8. The continuous production of stir cast material

    NASA Astrophysics Data System (ADS)

    Hamoen, A.

    1986-06-01

    The production of AlSi8 extrusion billets using a semicontinuous caster is described. The continuous casting process and the process parameters are outlined. The mathematical model, developed to calculate the temperature distribution within the billet during casting as a function of the process parameters, is explained. Quality control focussed on inversion segregation which causes the formation of a surface layer with a different structure and composition, imposing peeling of billets. Product development focussed on the production of stir-cast material of the same AlSi8 alloy. The use of AlSi8 as a wrought alloy by modification of the structure by stirring is discussed.

  9. Usefulness of three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging to detect inner-ear abnormalities in patients with sudden sensorineural hearing loss.

    PubMed

    Tanigawa, T; Shibata, R; Tanaka, H; Gosho, M; Katahira, N; Horibe, Y; Nakao, Y; Ueda, H

    2015-01-01

    Three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging has been used to detect alterations in the composition of inner-ear fluid. This study investigated the association between hearing level and the signal intensity of pre- and post-contrast three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging in patients with sudden-onset sensorineural hearing loss. Three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging was performed in 18 patients with sudden-onset sensorineural hearing loss: 12 patients with mild-to-moderate sensorineural hearing loss (baseline hearing levels of 60 dB or less) and 6 patients with severe-to-profound sensorineural hearing loss (baseline hearing levels of more than 60 dB). High-intensity signals in the inner ear were observed in two of the six patients (33 per cent) with severe-to-profound sensorineural hearing loss, but not in those with mild-to-moderate sensorineural hearing loss (mid-p test, p = 0.049). These signals were observed on magnetic resonance imaging scans 6 or 18 days after sensorineural hearing loss onset. The results indicate that three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging is not a useful tool for detecting inner-ear abnormalities in patients with mild sensorineural hearing loss.

  10. Fluid-Attenuated Inversion Recovery Vascular Hyperintensity Topography, Novel Imaging Marker for Revascularization in Middle Cerebral Artery Occlusion.

    PubMed

    Liu, Dezhi; Scalzo, Fabien; Rao, Neal M; Hinman, Jason D; Kim, Doojin; Ali, Latisha K; Saver, Jeffrey L; Sun, Wen; Dai, Qiliang; Liu, Xinfeng; Liebeskind, David S

    2016-11-01

    In acute arterial occlusion, fluid-attenuated inversion recovery vascular hyperintensity (FVH) has been linked to slow flow in leptomeningeal collaterals and cerebral hypoperfusion, but the impact on clinical outcome is still controversial. In this study, we aimed to investigate the association between FVH topography or FVH-Alberta Stroke Program Early CT Score (ASPECTS) pattern and outcome in acute M1-middle cerebral artery occlusion patients with endovascular treatment. We included acute M1-middle cerebral artery occlusion patients treated with endovascular therapy (ET). All patients had diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery before ET. Distal FVH-ASPECTS was evaluated according to distal middle cerebral artery-ASPECT area (M1-M6) and acute DWI lesion was also reviewed. The presence of FVH inside and outside DWI-positive lesions was separately analyzed. Clinical outcome after ET was analyzed with respect to different distal FVH-ASPECTS topography. Among 101 patients who met inclusion criteria for the study, mean age was 66.2±17.8 years and median National Institutes of Health Stroke Scale was 17.0 (interquartile range, 12.0-21.0). FVH-ASPECTS measured outside of the DWI lesion was significantly higher in patients with good outcome (modified Rankin Scale [mRS] score of 0-2; 8.0 versus 4.0, P<0.001). Logistic regression demonstrated that FVH-ASPECTS outside of the DWI lesion was independently associated with clinical outcome of these patients (odds ratio, 1.3; 95% confidence interval, 1.06-1.68; P=0.013). FVH-ASPECTS inside the DWI lesion was associated with hemorrhagic transformation (odds ratio, 1.3; 95% confidence interval, 1.04-1.51; P=0.019). Higher FVH-ASPECTS measured outside the DWI lesion is associated with good clinical outcomes in patients undergoing ET. FVH-ASPECTS measured inside the DWI lesion was predictive of hemorrhagic transformation. The FVH pattern, not number, can serve as an imaging selection marker for ET in

  11. Characteristic MRI findings in hyperglycaemia-induced seizures: diagnostic value of contrast-enhanced fluid-attenuated inversion recovery imaging.

    PubMed

    Lee, E J; Kim, K K; Lee, E K; Lee, J E

    2016-12-01

    To describe characteristic magnetic resonance imaging (MRI) abnormalities in hyperglycaemia-induced seizures, and evaluate the diagnostic value of contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging. Possible underlying mechanisms of this condition are also discussed. Eleven patients with hyperglycaemia-induced seizures and MRI abnormalities were retrospectively studied. Clinical manifestations, laboratory findings, MRI findings, and clinical outcomes were analysed. All patients, except one, presented with focal seizures, simple or complex partial seizures, or negative motor seizures. All patients had long-standing uncontrolled diabetes mellitus. The MRI abnormalities observed acutely were focal subcortical hypointensities on T2-weighted imaging and FLAIR imaging in all patients with overlying cortical gyral T2 hyperintensities in five. Focal overlying cortical or leptomeningeal enhancement on contrast-enhanced T1-weighted imaging or contrast-enhanced FLAIR imaging was observed in all patients. Contrast-enhanced FLAIR imaging was superior to contrast-enhanced T1-weighted imaging for detecting characteristic cortical or leptomeningeal enhancement. Diffusion-weighted imaging showed mildly restricted diffusion in four of five patients with cortical gyral T2 hyperintensity. In nine patients, the lesions were localised in the parietal or parieto-occipital lobes. The other two patients showed localised precentral gyral lesions. After treatment, the neurological symptoms, including the seizures, improved in all patients. On clinical recovery, the subcortical T2 hypointensity, gyral or leptomeningeal enhancement, and overlying cortical T2 hyperintensities resolved. Recognition of these radiological abnormalities in patients with hyperglycaemia-induced seizures is important in restricting unwarranted investigations and initiating early therapy. These patients generally have a good prognosis. Copyright © 2016 The Royal College of Radiologists. Published by

  12. Infrared properties of an anisotropically stirred fluid

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Barton, J. Michael

    1987-01-01

    A renormalization group is developed for the Navier-Stokes equations driven by an anisotropically correlated random stirring force. The stirring force generates homogeneous turbulence with a preferred direction. The force correlation is the sum of a small anisotropic perturbation and an isotropic correlation chosen, so that the fixed point of renormalization group has a k exp -5/3 energy spectrum. Fixed points for the anisotropic correlation are found near this isotropic fixed point. Two types of anisotropy are analyzed. when the additional stirring is in the plane perpendicular to the preferred direction, the renormalized viscosity is increased. When it is aligned with the preferred direction, the viscosity is decreased. A possible connection with the inverse energy cascade of two-dimensional turbulence is discussed.

  13. Application of variable threshold intensity to segmentation for white matter hyperintensities in fluid attenuated inversion recovery magnetic resonance images.

    PubMed

    Yoo, Byung Il; Lee, Jung Jae; Han, Ji Won; Oh, San Yeo Wool; Lee, Eun Young; MacFall, James R; Payne, Martha E; Kim, Tae Hui; Kim, Jae Hyoung; Kim, Ki Woong

    2014-04-01

    White matter hyperintensities (WMHs) are regions of abnormally high intensity on T2-weighted or fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI). Accurate and reproducible automatic segmentation of WMHs is important since WMHs are often seen in the elderly and are associated with various geriatric and psychiatric disorders. We developed a fully automated monospectral segmentation method for WMHs using FLAIR MRIs. Through this method, we introduce an optimal threshold intensity (I O ) for segmenting WMHs, which varies with WMHs volume (V WMH), and we establish the I O -V WMH relationship. Our method showed accurate validations in volumetric and spatial agreements of automatically segmented WMHs compared with manually segmented WMHs for 32 confirmatory images. Bland-Altman values of volumetric agreement were 0.96 ± 8.311 ml (bias and 95 % confidence interval), and the similarity index of spatial agreement was 0.762 ± 0.127 (mean ± standard deviation). Furthermore, similar validation accuracies were obtained in the images acquired from different scanners. The proposed segmentation method uses only FLAIR MRIs, has the potential to be accurate with images obtained from different scanners, and can be implemented with a fully automated procedure. In our study, validation results were obtained with FLAIR MRIs from only two scanner types. The design of the method may allow its use in large multicenter studies with correct efficiency.

  14. Comparison of Diffuse Weighted Imaging and Fluid Attenuation Inversion Recovery Sequences of MRI in Brain Multiple Sclerosis Plaques Detection.

    PubMed

    Nafisi-Moghadam, Reza; Rahimdel, Abolghasem; Shanbehzadeh, Tahereh; Fallah, Razieh

    2017-01-01

    Suitable magnetic resonance imaging (MRI) techniques from conventional to new devices can help physicians in diagnosis and follow up of Multiple Sclerosis (MS) patients. The aim of present research was to compare effectiveness of Fluid Attenuation Inversion Recovery (FLAIR) sequence of conventional MRI and Diffuse Weighted Imaging (DWI) sequence as a new technique in detection of brain MS plaques. In this analytic cross sectional study, sample size was assessed as 40 people to detect any significant difference between two sequences with a level of 0.05. DWI and FLAIR sequences of without contrast brain MRI of consecutive MS patients referred to MRI center of Shahid Sadoughi Hospital, Yazd, Iran from January to May 2012, were evaluated. Thirty-two females and 8 males with mean age of 35.20±9.80 yr (range = 11-66 yr) were evaluated and finally 340 plaques including 127(37.2%) in T2WI, 127(37.2%) in FLAIR, 63(18.5%) in DWI and 24(7.1%) in T1WI were detected. FLAIR sequence was more efficient than DWI in detection of brain MS plaques, oval, round, amorphous plaque shapes, frontal and occipital lobes, periventricular, intracapsular, corpus callosum, centrum semiovale, subcortical, basal ganglia plaques and diameter of detected MS plaques in DWI sequence was smaller than in FLAIR. Old lesion can be detected by conventional MRI and new techniques might be more useful in early inflammatory phase of MS and assessment of experimental treatments.

  15. SAR and scan-time optimized 3D whole-brain double inversion recovery imaging at 7T.

    PubMed

    Pracht, Eberhard D; Feiweier, Thorsten; Ehses, Philipp; Brenner, Daniel; Roebroeck, Alard; Weber, Bernd; Stöcker, Tony

    2017-09-14

    The aim of this project was to implement an ultra-high field (UHF) optimized double inversion recovery (DIR) sequence for gray matter (GM) imaging, enabling whole brain coverage in short acquisition times ( ≈5 min, image resolution 1 mm(3) ). A 3D variable flip angle DIR turbo spin echo (TSE) sequence was optimized for UHF application. We implemented an improved, fast, and specific absorption rate (SAR) efficient TSE imaging module, utilizing improved reordering. The DIR preparation was tailored to UHF application. Additionally, fat artifacts were minimized by employing water excitation instead of fat saturation. GM images, covering the whole brain, were acquired in 7 min scan time at 1 mm isotropic resolution. SAR issues were overcome by using a dedicated flip angle calculation considering SAR and SNR efficiency. Furthermore, UHF related artifacts were minimized. The suggested sequence is suitable to generate GM images with whole-brain coverage at UHF. Due to the short total acquisition times and overall robustness, this approach can potentially enable DIR application in a routine setting and enhance lesion detection in neurological diseases. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  16. Problems with diagnosis by fluid-attenuated inversion recovery magnetic resonance imaging in patients with acute aneurysmal subarachnoid hemorrhage.

    PubMed

    Shimoda, Masami; Hoshikawa, Kaori; Shiramizu, Hideki; Oda, Shinri; Matsumae, Mitsunori

    2010-01-01

    The diagnostic efficacy of fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging and computed tomography (CT) for acute subarachnoid hemorrhage (SAH) were compared and the problems with diagnosis were investigated in 81 patients with aneurysmal SAH within 24 hours after onset who underwent FLAIR imaging and CT on admission. The number of hematomas in the cisterns and ventricles were evaluated by clot scores. In addition, the frequency of undetected hematomas was calculated for the cisterns and ventricles. Clot scores were significantly higher for FLAIR imaging than for CT in the lateral sylvian, quadrigeminal, and convexity cisterns. On the other hand, clot scores were significantly higher for CT than for FLAIR imaging in the interhemispheric and medial sylvian cisterns. The overall frequency of undetected SAH was 2% for FLAIR imaging and 14% for CT. With the exception of the interhemispheric and medial sylvian cisterns, the frequency of undetected SAH was higher for CT than for FLAIR imaging. In this study, FLAIR imaging was more sensitive than CT for the detection of acute SAH within 24 hours after onset. However, the diagnostic efficacy of FLAIR imaging was reduced in comparatively tight cisterns.

  17. Prediction of Stroke Onset Is Improved by Relative Fluid-Attenuated Inversion Recovery and Perfusion Imaging Compared to the Visual Diffusion-Weighted Imaging/Fluid-Attenuated Inversion Recovery Mismatch.

    PubMed

    Wouters, Anke; Dupont, Patrick; Norrving, Bo; Laage, Rico; Thomalla, Götz; Albers, Gregory W; Thijs, Vincent; Lemmens, Robin

    2016-10-01

    Acute stroke patients with unknown time of symptom onset are ineligible for thrombolysis. The diffusion-weighted imaging and fluid-attenuated inversion recovery (FLAIR) mismatch is a reasonable predictor of stroke within 4.5 hours of symptom onset, and its clinical usefulness in selecting patients for thrombolysis is currently being investigated. The accuracy of the visual mismatch rating is moderate, and we hypothesized that the predictive value of stroke onset within 4.5 hours could be improved by including various clinical and imaging parameters. In this study, 141 patients in whom magnetic resonance imaging was obtained within 9 hours after symptom onset were included. Relative FLAIR signal intensity was calculated in the region of nonreperfused core. Mean Tmax was calculated in the total region with Tmax >6 s. Mean relative FLAIR, mean Tmax, lesion volume with Tmax >6 s, age, site of arterial stenosis, core volume, and location of infarct were analyzed by logistic regression to predict stroke onset time before or after 4.5 hours. Receiver-operating characteristic curve analysis revealed an area under the curve of 0.68 (95% confidence interval 0.59-0.78) for the visual diffusion-weighted imaging/FLAIR mismatch, thereby correctly classifying 69% of patients with an onset time before or after 4.5 hours. Age, relative FLAIR, and Tmax increased the accuracy significantly (P<0.01) to an area under the curve of 0.82 (95% confidence interval 0.74-0.89). This new predictive model correctly categorized 77% of patients according to stroke onset before versus after 4.5 hours. In patients with unknown stroke onset, the accuracy of predicting time from symptom onset within 4.5 hours is improved by obtaining relative FLAIR and perfusion imaging. © 2016 American Heart Association, Inc.

  18. Comparison of Diffuse Weighted Imaging and Fluid Attenuation Inversion Recovery Sequences of MRI in Brain Multiple Sclerosis Plaques Detection

    PubMed Central

    NAFISI-MOGHADAM, Reza; RAHIMDEL, Abolghasem; SHANBEHZADEH, Tahereh; FALLAH, Razieh

    2017-01-01

    Objective Suitable magnetic resonance imaging (MRI) techniques from conventional to new devices can help physicians in diagnosis and follow up of Multiple Sclerosis (MS) patients. The aim of present research was to compare effectiveness of Fluid Attenuation Inversion Recovery (FLAIR) sequence of conventional MRI and Diffuse Weighted Imaging (DWI) sequence as a new technique in detection of brain MS plaques. Materials & Methods In this analytic cross sectional study, sample size was assessed as 40 people to detect any significant difference between two sequences with a level of 0.05. DWI and FLAIR sequences of without contrast brain MRI of consecutive MS patients referred to MRI center of Shahid Sadoughi Hospital, Yazd, Iran from January to May 2012, were evaluated. Results Thirty-two females and 8 males with mean age of 35.20±9.80 yr (range = 11-66 yr) were evaluated and finally 340 plaques including 127(37.2%) in T2WI, 127(37.2%) in FLAIR, 63(18.5%) in DWI and 24(7.1%) in T1WI were detected. FLAIR sequence was more efficient than DWI in detection of brain MS plaques, oval, round, amorphous plaque shapes, frontal and occipital lobes, periventricular, intracapsular, corpus callosum, centrum semiovale, subcortical, basal ganglia plaques and diameter of detected MS plaques in DWI sequence was smaller than in FLAIR. Conclusion Old lesion can be detected by conventional MRI and new techniques might be more useful in early inflammatory phase of MS and assessment of experimental treatments. PMID:28277551

  19. Hyperintense vessels on acute stroke Fluid-attenuated Inversion Recovery imaging: Associations with clinical and other MRI findings

    PubMed Central

    Cheng, Bastian; Ebinger, Martin; Kufner, Anna; Köhrmann, Martin; Wu, Ona; Kang, Dong-Wha; Liebeskind, David; Tourdias, Thomas; Singer, Oliver C.; Christensen, Soren; Warach, Steve; Luby, Marie; Fiebach, Jochen B.; Fiehler, Jens; Gerloff, Christian; Thomalla, Götz

    2012-01-01

    Background and Purpose Hyperintense vessels (HV) have been observed in Fluid-Attenuated Inversion Recovery (FLAIR) imaging of patients with acute ischemic stroke and been linked to slow flow in collateral arterial circulation. Given the potential importance of HV, we used a large, multicentre dataset of stroke patients to clarify which clinical and imaging factors play a role in HV. Methods We analyzed data of 516 patients from the previously published PRE-FLAIR study. Patients were studied by MRI within 12 hours of symptom onset. HV were defined as hyperintensities in FLAIR corresponding to the typical course of a blood vessel that was not considered the proximal, occluded main artery ipsilateral to the diffusion restriction. Presence of HV was rated by two observers and related to clinical and imaging findings. Results Presence of HV was identified in 240 of all 516 patients (47%). Patients with HV showed larger initial ischemic lesion volumes (median 12.3 vs. 4.9 ml; p<0.001) and a more severe clinical impairment (median NIHSS 10.5 vs. 6; p<0.001). In 198 patients with MR-angiography, HV were found in 80% of patients with vessel occlusion and in 17% without vessel occlusion. In a multivariable logistic regression model, vessel occlusion was associated with HV (OR 21.7%; 95% CI 9.6–49.9, p < 0.001). HV detected vessel occlusion with a specificity of 0.86 (95% CI 0.80–0.90) and sensitivity of 0.76 (95% CI 0.69–0.83). Conclusions HV are a common finding associated with proximal arterial occlusions and more severe strokes. HV predict arterial occlusion with high diagnostic accuracy. PMID:22933582

  20. Fluid-attenuated inversion recovery hyperintensity correlates with matrix metalloproteinase-9 level and hemorrhagic transformation in acute ischemic stroke.

    PubMed

    Jha, Ruchira; Battey, Thomas W K; Pham, Ly; Lorenzano, Svetlana; Furie, Karen L; Sheth, Kevin N; Kimberly, W Taylor

    2014-04-01

    Matrix metalloproteinase-9 (MMP-9) is elevated in patients with acute stroke who later develop hemorrhagic transformation (HT). It is controversial whether early fluid-attenuated inversion recovery (FLAIR) hyperintensity on brain MRI predicts hemorrhagic transformation (HT). We assessed whether FLAIR hyperintensity was associated with MMP-9 and HT. We analyzed a prospectively collected cohort of acute stroke subjects with acute brain MRI images and MMP-9 values within the first 12 hours after stroke onset. FLAIR hyperintensity was measured using a signal intensity ratio between the stroke lesion and corresponding normal contralateral hemisphere. MMP-9 was measured using enzyme-linked immunosorbent assay. The relationships between FLAIR ratio (FR), MMP-9, and HT were evaluated. A total of 180 subjects were available for analysis. Patients were imaged with brain MRI at 5.6±4.3 hours from last seen well time. MMP-9 blood samples were drawn within 7.7±4.0 hours from last seen well time. The time to MRI (r=0.17, P=0.027) and MMP-9 level (r=0.29, P<0.001) were each associated with FR. The association between MMP-9 and FR remained significant after multivariable adjustment (P<0.001). FR was also associated with HT and symptomatic hemorrhage (P=0.012). FR correlates with both MMP-9 level and risk of hemorrhage. FLAIR changes in the acute phase of stroke may predict hemorrhagic transformation, possibly as a reflection of altered blood-brain barrier integrity.

  1. Ivy Sign on Fluid-Attenuated Inversion Recovery Images in Moyamoya Disease: Correlation with Clinical Severity and Old Brain Lesions

    PubMed Central

    Seo, Kwon-Duk; Suh, Sang Hyun; Kim, Yong Bae; Kim, Ji Hwa; Ahn, Sung Jun; Kim, Dong-Seok

    2015-01-01

    Purpose Leptomeningeal collateral, in moyamoya disease (MMD), appears as an ivy sign on fluid-attenuated inversion-recovery (FLAIR) images. There has been little investigation into the relationship between presentation of ivy signs and old brain lesions. We aimed to evaluate clinical significance of ivy signs and whether they correlate with old brain lesions and the severity of clinical symptoms in patients with MMD. Materials and Methods FLAIR images of 83 patients were reviewed. Each cerebral hemisphere was divided into 4 regions and each region was scored based on the prominence of the ivy sign. Total ivy score (TIS) was defined as the sum of the scores from the eight regions and dominant hemispheric ivy sign (DHI) was determined by comparing the ivy scores from each hemisphere. According to the degree of ischemic symptoms, patients were classified into four subgroups: 1) nonspecific symptoms without motor weakness, 2) single transient ischemic attack (TIA), 3) recurrent TIA, or 4) complete stroke. Results TIS was significantly different as follows: 4.86±2.55 in patients with nonspecific symptoms, 5.89±3.10 in patients with single TIA, 9.60±3.98 in patients with recurrent TIA and 8.37±3.39 in patients with complete stroke (p=0.003). TIS associated with old lesions was significantly higher than those not associated with old lesions (9.35±4.22 vs. 7.49±3.37, p=0.032). We found a significant correlation between DHI and motor symptoms (p=0.001). Conclusion Because TIS has a strong tendency with severity of ischemic motor symptom and the presence of old lesions, the ivy sign may be useful in predicting severity of disease progression. PMID:26256975

  2. Ivy Sign on Fluid-Attenuated Inversion Recovery Images in Moyamoya Disease: Correlation with Clinical Severity and Old Brain Lesions.

    PubMed

    Seo, Kwon-Duk; Suh, Sang Hyun; Kim, Yong Bae; Kim, Ji Hwa; Ahn, Sung Jun; Kim, Dong-Seok; Lee, Kyung-Yul

    2015-09-01

    Leptomeningeal collateral, in moyamoya disease (MMD), appears as an ivy sign on fluid-attenuated inversion-recovery (FLAIR) images. There has been little investigation into the relationship between presentation of ivy signs and old brain lesions. We aimed to evaluate clinical significance of ivy signs and whether they correlate with old brain lesions and the severity of clinical symptoms in patients with MMD. FLAIR images of 83 patients were reviewed. Each cerebral hemisphere was divided into 4 regions and each region was scored based on the prominence of the ivy sign. Total ivy score (TIS) was defined as the sum of the scores from the eight regions and dominant hemispheric ivy sign (DHI) was determined by comparing the ivy scores from each hemisphere. According to the degree of ischemic symptoms, patients were classified into four subgroups: 1) nonspecific symptoms without motor weakness, 2) single transient ischemic attack (TIA), 3) recurrent TIA, or 4) complete stroke. TIS was significantly different as follows: 4.86±2.55 in patients with nonspecific symptoms, 5.89±3.10 in patients with single TIA, 9.60±3.98 in patients with recurrent TIA and 8.37±3.39 in patients with complete stroke (p=0.003). TIS associated with old lesions was significantly higher than those not associated with old lesions (9.35±4.22 vs. 7.49±3.37, p=0.032). We found a significant correlation between DHI and motor symptoms (p=0.001). Because TIS has a strong tendency with severity of ischemic motor symptom and the presence of old lesions, the ivy sign may be useful in predicting severity of disease progression.

  3. Noninvasive investigation of exocrine pancreatic function: Feasibility of cine dynamic MRCP with a spatially selective inversion-recovery pulse.

    PubMed

    Yasokawa, Kazuya; Ito, Katsuyoshi; Tamada, Tsutomu; Yamamoto, Akira; Hayashida, Minoru; Tanimoto, Daigo; Higaki, Atsushi; Noda, Yasufumi; Kido, Ayumu

    2015-11-01

    To investigate the feasibility of noncontrast-enhanced cine dynamic magnetic resonance cholangiopancreatography (MRCP) with a spatially selective inversion-recovery (IR) pulse for evaluating exocrine pancreatic function in comparison with the N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) test as a pancreatic exocrine function test. Twenty subjects with or without chronic pancreatitis were included. MRCP with a spatially selective IR pulse was repeated every 15 seconds for 5 minutes to acquire a total of 20 images (cine-dynamic MRCP). The median and mean frequency of the observation (the number of times) and the moving distance (mean secretion grading scores) of pancreatic juice inflow on cine-dynamic MRCP were compared with a BT-PABA test. The urinary PABA excretion rate (%) had significant positive correlations with both the mean secretion grade (r = 0.66, P = 0.002) and frequency of secretory inflow (r = 0.62, P = 0.004) in cine dynamic MRCP. Both the mean frequency of observations of pancreatic secretory inflow (1.4 ± 1.6 times vs. 14.3 ± 4.2 times, P < 0.001) and the mean secretion grade (grade = 0.16 ± 0.24 vs. grade = 1.81 ± 0.81, P < 0.001) was significantly lower in the chronic pancreatitis group than in the normal subject group. Cine dynamic MRCP with a spatially selective IR pulse may have potential for estimating the pancreatic exocrine function noninvasively as a substitute for the BT-PABA test. © 2015 Wiley Periodicals, Inc.

  4. Friction stir welding tool

    DOEpatents

    Tolle; Charles R. , Clark; Denis E. , Barnes; Timothy A.

    2008-04-15

    A friction stir welding tool is described and which includes a shank portion; a shoulder portion which is releasably engageable with the shank portion; and a pin which is releasably engageable with the shoulder portion.

  5. Friction stir welding tool

    DOEpatents

    Tolle, Charles R.; Clark, Denis E.; Barnes, Timothy A.

    2008-04-15

    A friction stir welding tool is described and which includes a shank portion; a shoulder portion which is releasably engageable with the shank portion; and a pin which is releasably engageable with the shoulder portion.

  6. Friction-Stir Processing

    DTIC Science & Technology

    2006-01-01

    fatigue results for friction stir welded 2219 aluminum in the following conditions: 1) milled, 2) milled + LPB, 3) milled + 100 hours in a salt...same alloy following friction stir processing. Increased fatigue life in 5083-H321 aluminum fusion welds It will not be possible to friction...fine grain and weld defects near the surface will be eliminated. Potential benefits include both increased corrosion resistance and fatigue life

  7. Friction Stir Welding Development

    NASA Technical Reports Server (NTRS)

    Romine, Peter L.

    1998-01-01

    The research of this summer was a continuation of work started during the previous summer faculty fellowship period. The Friction Stir Welding process (FSW) patented by The Welding Institute (TWI), in Great Britain, has become a popular topic at the Marshall Space Flight Center over the past year. Last year it was considered a novel approach to welding but few people took it very seriously as a near term solution. However, due to continued problems with cracks in the new aluminum-lithium space shuttle external tank (ET), the friction stir process is being mobilized at full speed in an effort to mature this process for the potential manufacture of flight hardware. It is now the goal of NASA and Lockheed-Martin Corporation (LMC) to demonstrate a full-scale friction stir welding system capable of welding ET size barrel sections. The objectives this summer were: (1) Implementation and validation of the rotating dynamometer on the MSFC FSW system; (2) Collection of data for FSW process modeling efforts; (3) Specification development for FSW implementation on the vertical weld tool; (4) Controls and user interface development for the adjustable pin tool; and (5) Development of an instrumentation system for the planishing process. The projects started this summer will lead to a full scale friction stir welding system that is expected to produce a friction stir welded shuttle external tank type barrel section. The success of this could lead to the implementation of the friction stir process for manufacturing future shuttle external tanks.

  8. Evolution of Volume and Signal Intensity on Fluid-attenuated Inversion Recovery MR Images after Endovascular Stroke Therapy.

    PubMed

    Federau, Christian; Mlynash, Michael; Christensen, Soren; Zaharchuk, Greg; Cha, Brannon; Lansberg, Maarten G; Wintermark, Max; Albers, Gregory W

    2016-07-01

    Purpose To analyze both volume and signal evolution on magnetic resonance (MR) fluid-attenuated inversion recovery (FLAIR) images between the images after endovascular therapy and day 5 (which was the prespecified end point for infarct volume in the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution [DEFUSE 2] trial) in a subset of patients enrolled in the DEFUSE 2 study. Materials and Methods This study was approved by the local ethics committee at all participating sites. Informed written consent was obtained from all patients. In this post hoc analysis of the DEFUSE 2 study, 35 patients with FLAIR images acquired both after endovascular therapy (median time after symptom onset, 12 hours) and at day 5 were identified. Patients were separated into two groups based on the degree of reperfusion achieved on time to maximum greater than 6-second perfusion imaging (≥90% vs <90%). After coregistration and signal normalization, lesion volumes and signal intensity were assessed by using FLAIR imaging for the initial lesion (ie, visible after endovascular therapy) and the recruited lesion (the additional lesion visible on day 5, but not visible after endovascular therapy). Statistical significance was assessed by using Wilcoxon signed-rank, Mann-Whitney U, and Fisher exact tests. Results All 35 patients had FLAIR lesion growth between the after-revascularization examination and day 5. Median lesion growth was significantly larger in patients with <90% reperfusion (27.85 mL) compared with ≥90% (8.12 mL; P = .003). In the initial lesion, normalized signal did not change between after endovascular therapy (median, 1.60) and day 5 (median, 1.58) in the ≥90% reperfusion group (P = .97), but increased in the <90% reperfusion group (from 1.60 to 1.73; P = .01). In the recruited lesion, median normalized signal increased significantly in both groups between after endovascular therapy and day 5 (after endovascular therapy, from 1.19 to 1.56, P

  9. Triple-layer appearance of Brodmann area 4 at thin-section double inversion-recovery MR imaging.

    PubMed

    Kim, Eung Yeop; Kim, Dong-Hyun; Chang, Jong-Hee; Yoo, Eunhye; Lee, Jae-Wook; Park, Hae-Jeong

    2009-02-01

    To investigate whether thin-section axial double inversion-recovery (DIR) brain magnetic resonance (MR) imaging at 3.0 T can help distinguish the primary motor cortex (PMC), or Brodmann area 4, from other selected cortical regions, including the primary sensory cortex (PSC), or Brodmann areas 1-3, on the basis of the presence of a "triple-layer" appearance. This prospective study was approved by the institutional review board; informed consent was obtained from patients. This study included 191 patients (94 female, age range, 5-80 years; 97 male, age range, 5-76 years) with normal findings at 3.0-T MR imaging. The presence or absence of a triple-layer appearance within selected cortical regions on DIR images was graded independently by two neuroradiologists as definitely present (grade 2), probably present (grade 1), or definitely absent (grade 0). Ten additional patients with tumors underwent DIR imaging and intraoperative cortical mapping for further validation of the PMC. A myelin-stained brain specimen image in a patient not imaged with DIR was correlated with a representative set of DIR images. A triple-layer appearance was found in the PMC bilaterally in 184 of 191 patients; grade 0 was assigned in only seven patients, who were all younger than 10 years. Grades were significantly lower in patients younger than 10 years than in others (P < .0001) but were not significantly different between older age groups (P > .0018). Interobserver agreement was excellent (weighted kappa = 0.843). The PMC determined on DIR images was confirmed with cortical mapping in all 10 patients with tumors. Triple-layer appearance was not present in the other cortical regions examined, including the PSC (P < .01). The triple-layer appearance on DIR images corresponded to the myelin band within the PMC present on the myelin-stained specimen image. A triple-layer appearance was found in the PMC at thin-section 3.0-T DIR imaging but not in other examined brain regions and therefore might

  10. Modified look-locker inversion recovery T1 mapping indices: assessment of accuracy and reproducibility between magnetic resonance scanners

    PubMed Central

    2013-01-01

    Background Cardiovascular magnetic resonance (CMR) T1 mapping indices, such as T1 time and partition coefficient (λ), have shown potential to assess diffuse myocardial fibrosis. The purpose of this study was to investigate how scanner and field strength variation affect the accuracy and precision/reproducibility of T1 mapping indices. Methods CMR studies were performed on two 1.5T and three 3T scanners. Eight phantoms were made to mimic the T1/T2 of pre- and post-contrast myocardium and blood at 1.5T and 3T. T1 mapping using MOLLI was performed with simulated heart rate of 40-100 bpm. Inversion recovery spin echo (IR-SE) was the reference standard for T1 determination. Accuracy was defined as the percent error between MOLLI and IR-SE, and scan/re-scan reproducibility was defined as the relative percent mean difference between repeat MOLLI scans. Partition coefficient was estimated by ΔR1myocardium phantom/ΔR1blood phantom. Generalized linear mixed model was used to compare the accuracy and precision/reproducibility of T1 and λ across field strength, scanners, and protocols. Results Field strength significantly affected MOLLI T1 accuracy (6.3% error for 1.5T vs. 10.8% error for 3T, p<0.001) but not λ accuracy (8.8% error for 1.5T vs. 8.0% error for 3T, p=0.11). Partition coefficients of MOLLI were not different between two 1.5T scanners (47.2% vs. 47.9%, p=0.13), and showed only slight variation across three 3T scanners (49.2% vs. 49.8% vs. 49.9%, p=0.016). Partition coefficient also had significantly lower percent error for precision (better scan/re-scan reproducibility) than measurement of individual T1 values (3.6% for λ vs. 4.3%-4.8% for T1 values, approximately, for pre/post blood and myocardium values). Conclusion Based on phantom studies, T1 errors using MOLLI ranged from 6-14% across various MR scanners while errors for partition coefficient were less (6-10%). Compared with absolute T1 times, partition coefficient showed less variability across

  11. The leptomeningeal ivy sign on fluid-attenuated inversion recovery images in moyamoya disease: positron emission tomography study.

    PubMed

    Kaku, Yasuyuki; Iihara, Koji; Nakajima, Norio; Kataoka, Hiroharu; Fukushima, Kazuhito; Iida, Hidehiro; Hashimoto, Nobuo

    2013-01-01

    The ivy sign is sometimes seen on fluid-attenuated inversion recovery (FLAIR) images in moyamoya disease (MMD). In recent studies using single-photon emission computed tomography, ivy sign proliferation correlated with decreases in cerebrovascular reserve. However, a decreased vascular reserve is not concrete. The purpose of this study was to evaluate the correlation between ivy sign proliferation and the findings of 15O gas positron emission tomography (PET). In 19 MMD patients (12 women, age 31-69 years) with ischemic symptoms, FLAIR magnetic resonance imaging and 15O gas PET were performed. We classified the middle cerebral artery (MCA) territory into 2 regions in each hemisphere, and the degree of the ivy sign (ivy sign score) in each region was classified into 3 grades (0-2), where grade 0 indicated an absence of the ivy sign, grade 1 indicated that the ivy sign was seen on less than half of the cortical surface in each region, and grade 2 indicated that the ivy sign was seen on more than half of the cortical surface. We examined the relationship among the ivy sign score, the severity of ischemic symptoms and PET parameters in 76 MCA regions of 19 patients. Ivy sign scores of the regions were 0 (n = 19), 1 (n = 40), and 2 (n = 17). Total ivy sign score of a hemisphere increased as clinical symptoms became more severe. Cerebral blood flow (CBF) values were lower, cerebral blood volume (CBV) values were higher, and CBF/CBV values were lower than those of controls as symptoms became severe (p < 0.05). CBF and CBF/CBV values decreased and CBV values increased as the ivy sign score increased, and were significantly higher and lower, respectively, than control values (p < 0.05). No significant differences in cerebral metabolic rate of oxygen and oxygen extraction fraction were found between the 3 ivy sign scores. A positive correlation was found between ivy sign score and increases in CBV (p < 0.01), and a more obvious negative correlation was found between ivy sign

  12. High-resolution myocardial T1 mapping using single-shot inversion recovery fast low-angle shot MRI with radial undersampling and iterative reconstruction

    PubMed Central

    Joseph, Arun A; Kalentev, Oleksandr; Merboldt, Klaus-Dietmar; Voit, Dirk; Roeloffs, Volkert B; van Zalk, Maaike; Frahm, Jens

    2016-01-01

    Objective: To develop a novel method for rapid myocardial T1 mapping at high spatial resolution. Methods: The proposed strategy represents a single-shot inversion recovery experiment triggered to early diastole during a brief breath-hold. The measurement combines an adiabatic inversion pulse with a real-time readout by highly undersampled radial FLASH, iterative image reconstruction and T1 fitting with automatic deletion of systolic frames. The method was implemented on a 3-T MRI system using a graphics processing unit-equipped bypass computer for online application. Validations employed a T1 reference phantom including analyses at simulated heart rates from 40 to 100 beats per minute. In vivo applications involved myocardial T1 mapping in short-axis views of healthy young volunteers. Results: At 1-mm in-plane resolution and 6-mm section thickness, the inversion recovery measurement could be shortened to 3 s without compromising T1 quantitation. Phantom studies demonstrated T1 accuracy and high precision for values ranging from 300 to 1500 ms and up to a heart rate of 100 beats per minute. Similar results were obtained in vivo yielding septal T1 values of 1246 ± 24 ms (base), 1256 ± 33 ms (mid-ventricular) and 1288 ± 30 ms (apex), respectively (mean ± standard deviation, n = 6). Conclusion: Diastolic myocardial T1 mapping with use of single-shot inversion recovery FLASH offers high spatial resolution, T1 accuracy and precision, and practical robustness and speed. Advances in knowledge: The proposed method will be beneficial for clinical applications relying on native and post-contrast T1 quantitation. PMID:27759423

  13. Recovery

    NASA Image and Video Library

    This video discusses the recovery events that occur in high-power rocketry and the various devices used in safely recovering the rocket. The video includes a discussion of black powder and ejection...

  14. Texture Development in Friction Stir Welds

    DTIC Science & Technology

    2011-01-01

    distor- tion). Friction stir welding was initially developed for aluminium alloys, but has since been demonstrated for copper, iron, titanium and...textures. The predominant mode of deformation, particularly in regions near the tool, is simple shear, as confirmed in previous FSW studies of aluminium ...alloys.3–8 It has been demonstrated that continuous dynamic recrystallisation, i.e. the concurrent processes of deformation and dynamic recovery, is

  15. An inverse problem approach to recovery of in vivo nanoparticle concentrations from thermal image monitoring of MR-guided laser induced thermal therapy.

    PubMed

    Fuentes, D; Elliott, A; Weinberg, J S; Shetty, A; Hazle, J D; Stafford, R J

    2013-01-01

    Quantification of local variations in the optical properties of tumor tissue introduced by the presence of gold-silica nanoparticles (NP) presents significant opportunities in monitoring and control of NP-mediated laser induced thermal therapy (LITT) procedures. Finite element methods of inverse parameter recovery constrained by a Pennes bioheat transfer model were applied to estimate the optical parameters. Magnetic resonance temperature imaging (MRTI) acquired during a NP-mediated LITT of a canine transmissible venereal tumor in brain was used in the presented statistical inverse problem formulation. The maximum likelihood (ML) value of the optical parameters illustrated a marked change in the periphery of the tumor corresponding with the expected location of NP and area of selective heating observed on MRTI. Parameter recovery information became increasingly difficult to infer in distal regions of tissue where photon fluence had been significantly attenuated. Finite element temperature predictions using the ML parameter values obtained from the solution of the inverse problem are able to reproduce the NP selective heating within 5 °C of measured MRTI estimations along selected temperature profiles. Results indicate the ML solution found is able to sufficiently reproduce the selectivity of the NP mediated laser induced heating and therefore the ML solution is likely to return useful optical parameters within the region of significant laser fluence.

  16. Planar oscillatory stirring apparatus

    NASA Astrophysics Data System (ADS)

    Wolf, M. F.

    1985-08-01

    The present invention is directed to an apparatus for stirring materials using planar orthogonal axes oscillations. The apparatus has a movable slide plate sandwiched between two fixed parallel support plates. Pressurized air is supplied to the movable slide plate which employs a tri-arm air bearing vent structure which allows the slide plate to float and to translate between the parallel support plates. The container having a material to be stirred is secured to the upper surface of the slide plate through an aperture in the upper support plate. A motor driven eccentric shaft loosely extends into a center hole bearing of the slide plate to cause the horizontal oscillations. Novelty lies in the combination of elements which exploits the discovery that low frequency, orthogonal oscillations applied horizontally to a Bridgman crucible provides a very rigorous stirring action, comparable with and more effective by an order of magnitude than the accelerated crucible rotation technique.

  17. Utility of STIR MRI in pediatric cervical spine clearance after trauma.

    PubMed

    Henry, Mark; Scarlata, Katherine; Riesenburger, Ron I; Kryzanski, James; Rideout, Leslie; Samdani, Amer; Jea, Andrew; Hwang, Steven W

    2013-07-01

    Although MRI with short-term T1 inversion recovery (STIR) sequencing has been widely adopted in the clearance of cervical spine in adults who have sustained trauma, its applicability for cervical spine clearance in pediatric trauma patients remains unclear. The authors sought to review a Level 1 trauma center's experience using MRI for posttraumatic evaluation of the cervical spine in pediatric patients. A pediatric trauma database was retrospectively queried for patients who received an injury warranting radiographic imaging of the cervical spine and had a STIR-MRI sequence of the cervical spine performed within 48 hours of injury between 2002 and 2011. Demographic, radiographic, and outcome data were retrospectively collected through medical records. Seventy-three cases were included in the analysis. The mean duration of follow-up was 10 months (range 4 days-7 years). The mean age of the patients at the time of trauma evaluation was 8.3 ± 5.8 years, and 65% were male. The majority of patients were involved in a motor vehicle accident. In 70 cases, the results of MRI studies were negative, and the patients were cleared prior to discharge with no clinical suggestion of instability on follow-up. In 3 cases, the MRI studies had abnormal findings; 2 of these 3 patients were cleared with dynamic radiographs during the same admission. Only 1 patient had an unstable injury and required surgical stabilization. The sensitivity of STIR MRI to detect cervical instability was 100% with a specificity of 97%. The positive predictive value was 33% and the negative predictive value was 100%. Although interpretation of our results are diminished by limitations of the study, in our series, STIR MRI in routine screening for pediatric cervical trauma had a high sensitivity and slightly lower specificity, but may have utility in future practices and should be considered for implementation into protocols.

  18. Computational issues of importance to the inverse recovery of epicardial potentials in a realistic heart-torso geometry.

    PubMed

    Messinger-Rapport, B J; Rudy, Y

    1989-11-01

    In vitro data from a realistic-geometry electrolytic tank were used to demonstrate the consequences of computational issues critical to the ill-posed inverse problem in electrocardiography. The boundary element method was used to discretize the relationship between the body surface potentials and epicardial cage potentials. Variants of Tikhonov regularization were used to stabilize the inversion of the body surface potentials in order to reconstruct the epicardial surface potentials. The computational issues investigated were (1) computation of the regularization parameter; (2) effects of inaccuracy in locating the position of the heart; and (3) incorporation of a priori information on the properties of epicardial potentials into the regularization methodology. Two methods were suggested by which a priori information could be incorporated into the regularization formulation: (1) use of an estimate of the epicardial potential distribution everywhere on the surface and (2) use of regional bounds on the excursion of the potential. Results indicate that the a posteriori technique called CRESO, developed by Colli Franzone and coworkers, most consistently derives the regularization parameter closest to the optimal parameter for this experimental situation. The sensitivity of the inverse computation in a realistic-geometry torso to inaccuracies in estimating heart position are consistent with results from the eccentric spheres model; errors of 1 cm are well tolerated, but errors of 2 cm or greater result in a loss of position and amplitude information. Finally, estimates and bounds based on accurate, known information successfully lower the relative error associated with the inverse and have the potential to significantly enhance the amplitude and feature position information obtainable from the inverse-reconstructed epicardial potential map.

  19. Friction Stir Weld Tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  20. Friction stir weld tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  1. STIR: Advanced Quantum Sensing

    DTIC Science & Technology

    2014-07-18

    STIR: Advanced Quantum Sensing Recycling unmeasured photons in a system utilizing weak measurements can substantially improve the signal-to- noise...Quantum Sensing Report Title Recycling unmeasured photons in a system utilizing weak measurements can substantially improve the signal-to-noise ratio. We...Kevin Lyons, Andrew N. Jordan, Trent M. Graham, Paul G. Kwiat. Strengthening weak- value amplification with recycled photons , Physical Review A, (08

  2. Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and promises to be an important welding process for any industries where welds of optimal quality are demanded. This article provides an introduction to the FSW process. The chief concern is the physical effect of the tool on the weld metal: how weld seam bonding takes place, what kind of weld structure is generated, potential problems, possible defects for example, and implications for process parameters and tool design. Weld properties are determined by structure, and the structure of friction stir welds is determined by the weld metal flow field in the vicinity of the weld tool. Metal flow in the vicinity of the weld tool is explained through a simple kinematic flow model that decomposes the flow field into three basic component flows: a uniform translation, a rotating solid cylinder, and a ring vortex encircling the tool. The flow components, superposed to construct the flow model, can be related to particular aspects of weld process parameters and tool design; they provide a bridge to an understanding of a complex-at-first-glance weld structure. Torques and forces are also discussed. Some simple mathematical models of structural aspects, torques, and forces are included.

  3. The hyperintense acute reperfusion marker on fluid-attenuated inversion recovery magnetic resonance imaging is caused by gadolinium in the cerebrospinal fluid.

    PubMed

    Köhrmann, Martin; Struffert, Tobias; Frenzel, Thomas; Schwab, Stefan; Doerfler, Arnd

    2012-01-01

    The hyperintense acute reperfusion marker (HARM) on fluid-attenuated inversion recovery MRI is believed to be caused by gadolinium-based contrast agents crossing a disrupted blood-brain barrier. However, this hypothesis has never been directly verified in humans. In this study, we analyzed cerebrospinal fluid samples of patients with HARM on imaging regarding the presence and concentration of gadolinium-based contrast agents. Gadobutrol was found in concentrations of approximately 50 μmol/L. Using phantom MRI experiments, we demonstrate that the detected concentrations are consistent with the observed HARM imaging pattern. Our study yields first direct evidence in humans that the imaging phenomenon HARM is indeed caused by leakage of gadolinium-based contrast agents into the cerebrospinal fluid.

  4. Axial STIR MRI: a faster method for confirming femoral head reduction in DDH.

    PubMed

    Conroy, Eimear; Sproule, J; Timlin, M; McManus, F

    2009-06-01

    Non-concentric reduction of the femoral head within the acetabulum is detrimental to its delicate cartilaginous structure and may result in a growth disturbance. Successful relocation of the dislocated femoral head depends on subtle clinical findings and radiography. The combination of a dislocated femoral head and a severely dysplastic acetabulum can result in a clinical examination that is unhelpful in confirming reduction under anaesthesia. In cases where uncertainty existed regarding head reduction in a spica cast, we performed axial short inversion time inversion recovery (STIR) and axial proton density magnetic resonance imaging (MRI) scans. We retrospectively reviewed the efficiency and accuracy of MRI in confirming femoral head location after closed reduction and spica application in eight children. One hundred and fifty-three cases of developmental dysplasia were treated with examination under anaesthesia and spica application in our unit over a 3-year period. Eight cases where MRI scanning was performed were identified. Before application of the spica cast, we used radiographic screening to assess the stability of the reduction. Absence of the ossific nucleus within the femoral head made confirmation of the location with the image intensifier unreliable. To confirm concentric femoral head location after closed reduction and spica application, we performed an MRI scan in the immediate post-anaesthesia period. All scans were performed within 30 min of application of the spica, and the average time for each scan was 5 min. All eight children who had MRI post-application of the spica had concentric reduction of the femoral head. MRI allowed three-dimensional appreciation of the acetabulum and femoral head. Use of the axial STIR images allows accurate assessment of the cartilaginous ossific nucleus. All patients were discharged the same afternoon and followed up as outpatients. No patient in our group required contrast arthrography. While not indicated in all

  5. Assessment of the evaluation of liver T1 mapping imaging applying virtual ECG gating on a modified look-locker inversion recovery (MOLLI) pulse sequence

    NASA Astrophysics Data System (ADS)

    Yu, Seung-Man; Goo, Eun-Hoe; Lee, Suk-Jun; Choe, Bo-Young

    2014-10-01

    A T1 mapping calculation error may occur in a physicochemical environment with large relaxivity. We evaluated through a simulated electrocardiogram (ECG) the administration of a contrast with high relaxivity and its effect on the heart rate by using a modified Look-Locker inversion recovery (MOLLI) pulse sequence. The agarose 2% phantom of high relaxivity environment was developed by diluting gadoxetic acid magnetic resonance imaging (MRI) T1 contrast media. The gold standard T1 determination was based on coronal single section imaging with a 2D inversion-recovery turbo spin echo sequence (2D-IRTSE) in a 3T MR unit. Using the identical 3T MR scanner, we acquired T1 mapping for the MOLLI pulse sequence with various virtual heart rates. T1 mapping data of the two different pulse sequences ( i.e., 2D-IRTSE and MOLLI) were measured to investigate the accuracy and the specificity. An in vivo study was conducted in the same manner as the phantom experiments for liver T1 mapping imaging in three healthy volunteers. The MOLLI pulse sequence showed an error rate of less than 10% at a contrast agent concentration of 0.4 mmol/L, and significant error, compared with the reference value, was observed at 0.6 mmol/L or higher. The percentage error of the T1 value did not correlated with the RR ( i.e., the time between heart beats) change that was observed (P =.270). Based on the in-vivo liver test, T1 mapping imaging of an abdominal organ as the liver can be successfully achieved using the applied virtual ECG gating on the MOLLI sequence.

  6. Improving parenchyma segmentation by simultaneous estimation of tissue property T1 map and group-wise registration of inversion recovery MR breast images.

    PubMed

    Xing, Ye; Xue, Zhong; Englander, Sarah; Schnall, Mitchell; Shen, Dinggang

    2008-01-01

    The parenchyma tissue in the breast has a strong relation with predictive biomarkers of breast cancer. To better segment parenchyma, we perform segmentation on estimated tissue property T1 map. To improve the estimation of tissue property (T1) which is the basis for parenchyma segmentation, we present an integrated algorithm for simultaneous T1 map estimation, T1 map based parenchyma segmentation and group-wise registration on series of inversion recovery magnetic resonance (MR) breast images. The advantage of using this integrated algorithm is that the simultaneous T1 map estimation (E-step) and group-wise registration (R-step) could benefit each other and jointly improve parenchyma segmentation. In particular, in E-step, T1 map based segmentation could help perform an edge-preserving smoothing on the tentatively estimated noisy T1 map, and could also help provide tissue probability maps to be robustly registered in R-step. Meanwhile, the improved estimation of T1 map could help segment parenchyma in a more accurate way. In R-step, for robust registration, the group-wise registration is performed on the tissue probability maps produced in E-step, rather than the original inversion recovery MR images, since tissue probability maps are the intrinsic tissue property which is invariant to the use of different imaging parameters. The better alignment of images achieved in R-step can help improve T1 map estimation and indirectly the T1 map based parenchyma segmentation. By iteratively performing E-step and R-step, we can simultaneously obtain better results for T1 map estimation, T1 map based segmentation, group-wise registration, and finally parenchyma segmentation.

  7. Effect of Stirring Method on Protein Crystallization

    NASA Astrophysics Data System (ADS)

    Yaoi, Mari; Adachi, Hiroaki; Takano, Kazufumi; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Mori, Yusuke; Sasaki, Takatomo

    2004-10-01

    We previously proposed the use of solution stirring during the growth of protein crystals using the Micro-Stirring technique with a rotary shaker. In this paper, we report on the effects of a new type solution flow on the crystallization of hen egg-white lysozyme (HEWL) using a wave shaker. The time required for nucleation was reduced by wave stirring, but increased by rotary stirring. Nucleation was stimulated by wave stirring. This result indicates that protein crystal growth in a stirred solution is strongly dependent on the stirring method used and the solution flow. Therefore, optimized stirring conditions are essential for producing high-quality protein crystals.

  8. Electrical Monitoring of Fresh Water Displacement in a Brackish Aquifer During Aquifer Storage and Recovery: Forward and Inverse Modeling Results

    NASA Astrophysics Data System (ADS)

    Levannier, A.; Delhomme, J.

    2003-12-01

    Aquifer storage and recovery (ASR) projects are now used to temporarily store water in the subsurface and to recover it when needed. When freshwater is injected into a brackish aquifer, a transition zone forms, due to mixing, diffusion and gravity. The front displacement and the width of the transition zone depend on the characteristics of the aquifer but, from repeated surveys conducted with an array of downhole electrodes placed against the borehole wall, the changes in the front position/shape can be continuously monitored. Synthetic data were created for a targeted ASR situation through hydrodynamic and hydrodispersive modeling (performed with a finite difference scheme) that gave the salt concentration distribution in the aquifer, as a function of space and time, during ASR inject/store/pump cycles. Concentrations were converted first into water resistivity values Rw, and then into formation resistivity values Rt through Archie's law (1) calibrated on logging data: \\begin{equation} R_{t}=\\frac{a}{\\phi^{m}}R_w where φ is the porosity, and a and m depend on the lithology. Based on this information, the response of downhole electrodes was computed by solving equation (2) (using a finite element modeling code) for electrical surveys conducted at repeated times during the planned ASR cycles, and in particular during the initial ASR testing phase: \\begin{equation} \

  9. Mask pattern recovery by level set method based inverse inspection technology (IIT) and its application on defect auto disposition

    NASA Astrophysics Data System (ADS)

    Park, Jin-Hyung; Chung, Paul D. H.; Jeon, Chan-Uk; Cho, Han Ku; Pang, Linyong; Peng, Danping; Tolani, Vikram; Cecil, Tom; Kim, David; Baik, KiHo

    2009-10-01

    At the most advanced technology nodes, such as 32nm and 22nm, aggressive OPC and Sub-Resolution Assist Features (SRAFs) are required. However, their use results in significantly increased mask complexity, making mask defect disposition more challenging than ever. This paper describes how mask patterns can first be recovered from the inspection images by applying patented algorithms using Level Set Methods. The mask pattern recovery step is then followed by aerial/wafer image simulation, the results of which can be plugged into an automated mask defect disposition system based on aerial/wafer image. The disposition criteria are primarily based on wafer-plane CD variance. The system also connects to a post-OPC lithography verification tool that can provide gauges and CD specs, thereby enabling them to be used in mask defect disposition as well. Results on both programmed defects and production defects collected at Samsung mask shop are presented to show the accuracy and consistency of using the Level Set Methods and aerial/wafer image based automated mask disposition.

  10. Stirring turbulence with turbulence

    NASA Astrophysics Data System (ADS)

    Cekli, Hakki Ergun; Joosten, René; van de Water, Willem

    2015-12-01

    We stir wind-tunnel turbulence with an active grid that consists of rods with attached vanes. The time-varying angle of these rods is controlled by random numbers. We study the response of turbulence on the statistical properties of these random numbers. The random numbers are generated by the Gledzer-Ohkitani-Yamada shell model, which is a simple dynamical model of turbulence that produces a velocity field displaying inertial-range scaling behavior. The range of scales can be adjusted by selection of shells. We find that the largest energy input and the smallest anisotropy are reached when the time scale of the random numbers matches that of the largest eddies of the wind-tunnel turbulence. A large mismatch of these times creates a highly intermittent random flow with interesting but quite anomalous statistics.

  11. Thermal Stir Welds in Titanium

    NASA Astrophysics Data System (ADS)

    Fonda, Richard W.; Knipling, Keith E.; Pilchak, Adam L.

    2016-01-01

    Although conventional friction stir welding (FSW) has proven unsuccessful in joining thick sections of alpha and near-alpha titanium alloys, thermal stir welding, a variant of the FSW process in which an external heat source is used to preheat the workpiece, is demonstrated to be able to reliably join 12.3-mm-thick plates of CP titanium. This paper describes the microstructures and textures that develop in these thermal stir welds. The observed microstructure was used to reconstruct the high-temperature microstructure and texture present during the welding process and therefore reveal the genesis of the welding structures.

  12. Three-dimensional inversion recovery manganese-enhanced MRI of mouse brain using super-resolution reconstruction to visualize nuclei involved in higher brain function.

    PubMed

    Poole, Dana S; Plenge, Esben; Poot, Dirk H J; Lakke, Egbert A J F; Niessen, Wiro J; Meijering, Erik; van der Weerd, Louise

    2014-07-01

    The visualization of activity in mouse brain using inversion recovery spin echo (IR-SE) manganese-enhanced MRI (MEMRI) provides unique contrast, but suffers from poor resolution in the slice-encoding direction. Super-resolution reconstruction (SRR) is a resolution-enhancing post-processing technique in which multiple low-resolution slice stacks are combined into a single volume of high isotropic resolution using computational methods. In this study, we investigated, first, whether SRR can improve the three-dimensional resolution of IR-SE MEMRI in the slice selection direction, whilst maintaining or improving the contrast-to-noise ratio of the two-dimensional slice stacks. Second, the contrast-to-noise ratio of SRR IR-SE MEMRI was compared with a conventional three-dimensional gradient echo (GE) acquisition. Quantitative experiments were performed on a phantom containing compartments of various manganese concentrations. The results showed that, with comparable scan times, the signal-to-noise ratio of three-dimensional GE acquisition is higher than that of SRR IR-SE MEMRI. However, the contrast-to-noise ratio between different compartments can be superior with SRR IR-SE MEMRI, depending on the chosen inversion time. In vivo experiments were performed in mice receiving manganese using an implanted osmotic pump. The results showed that SRR works well as a resolution-enhancing technique in IR-SE MEMRI experiments. In addition, the SRR image also shows a number of brain structures that are more clearly discernible from the surrounding tissues than in three-dimensional GE acquisition, including a number of nuclei with specific higher brain functions, such as memory, stress, anxiety and reward behavior.

  13. STIR vs. T1-weighted fat-suppressed gadolinium-enhanced MRI of bone marrow edema of the knee: computer-assisted quantitative comparison and influence of injected contrast media volume and acquisition parameters.

    PubMed

    Mayerhoefer, Marius E; Breitenseher, Martin J; Kramer, Josef; Aigner, Nicolas; Norden, Cornelia; Hofmann, Siegfried

    2005-12-01

    To compare short tau inversion recovery (STIR) and T1-weighted (T1w) gadolinium (Gd)-enhanced fat-suppressed MRI of bone marrow edema (BME) of the knee, and investigate the influence of injected contrast media volume and variation of major acquisition parameters on apparent BME volume and signal contrast. STIR and T1w Gd-enhanced fat-suppressed images were obtained from 30 patients with BME of the knee. Two groups of patients were examined with different MR scanners, acquisition parameters, and contrast media volumes. For both sequences, BME volume and signal contrast were assessed by computer-assisted quantification, and were compared through their arithmetic means and correlation coefficients (r(2)). The injected contrast media volume was also correlated with BME volume and signal contrast differences between sequences. A strong correlation between the STIR and Gd-enhanced T1w images was found for BME volume (r(2) = 0.96-0.99) and BME signal contrast (r(2) = 0.86-0.94). Despite the differences in MR acquisition parameters and injected contrast media volume, both sequences depicted an almost identical BME volume in both groups. Contrast media volume showed a moderate correlation (r(2) = 0.40) with BME volume differences. STIR is the optimum method for determining the size and signal contrast of BME. The injected contrast media volume appears to have only a limited influence on apparent BME volume.

  14. Cerebrospinal Fluid Enhancement on Fluid Attenuated Inversion Recovery Images After Carotid Artery Stenting with Neuroprotective Balloon Occlusions: Hemodynamic Instability and Blood-Brain Barrier Disruption

    SciTech Connect

    Ogami, Ryo Nakahara, Toshinori; Hamasaki, Osamu; Araki, Hayato; Kurisu, Kaoru

    2011-10-15

    Purpose: A rare complication of carotid artery stenting (CAS), prolonged reversible neurological symptoms with delayed cerebrospinal fluid (CSF) space enhancement on fluid attenuated inversion recovery (FLAIR) images, is associated with blood-brain barrier (BBB) disruption. We prospectively identified patients who showed CSF space enhancement on FLAIR images. Methods: Nineteen patients-5 acute-phase and 14 scheduled-underwent 21 CAS procedures. Balloon catheters were navigated across stenoses, angioplasty was performed using a neuroprotective balloon, and stents were placed with after dilation under distal balloon protection. CSF space hyperintensity or obscuration on FLAIR after versus before CAS indicated CSF space enhancement. Correlations with clinical factors were examined. Results: CSF space was enhanced on FLAIR in 12 (57.1%) cases. Postprocedural CSF space enhancement was significantly related to age, stenosis rate, acute-stage procedure, and total occlusion time. All acute-stage CAS patients showed delayed enhancement. Only age was associated with delayed CSF space enhancement in scheduled CAS patients. Conclusions: Ischemic intolerance for severe carotid artery stenosis and temporary neuroprotective balloon occlusion, causing reperfusion injury, seem to be the main factors that underlie BBB disruption with delayed CSF space enhancement shortly after CAS, rather than sudden poststenting hemodynamic change. Our results suggest that factors related to hemodynamic instability or ischemic intolerance seem to be associated with post-CAS BBB vulnerability. Patients at risk for hemodynamic instability or with ischemic intolerance, which decrease BBB integrity, require careful management to prevent intracranial hemorrhagic and other post-CAS complications.

  15. T1-weighted gradient-echo imaging, with and without inversion recovery, in the identification of anatomical structures on the lateral surface of the brain*

    PubMed Central

    Georgeto, Sergio Murilo; Zicarelli, Carlos Alexandre Martins; Gariba, Munir Antônio; Aguiar, Luiz Roberto

    2016-01-01

    Objective To compare brain structures using volumetric magnetic resonance imaging with isotropic resolution, in T1-weighted gradient-echo (GRE) acquisition, with and without inversion recovery (IR). Materials and methods From 30 individuals, we evaluated 120 blocks of images of the left and right cerebral hemispheres being acquired by T1 GRE and by T1 IR GRE. On the basis of the Naidich et al. method for localization of anatomical landmarks, 27 anatomical structures were divided into two categories: identifiable and inconclusive. Those two categories were used in the analyses of repeatability (intraobserver agreement) and reproducibility (interobserver agreement). McNemar's test was used in order to compare the T1 GRE and T1 IR GRE techniques. Results There was good agreement in the intraobserver and interobserver analyses (mean kappa > 0.60). McNemar's test showed that the frequency of identifiable anatomical landmarks was slightly higher when the T1 IR GRE technique was employed than when the T1 GRE technique was employed. The difference between the two techniques was statistically significant. Conclusion In the identification of anatomical landmarks, the T1 IR GRE technique appears to perform slightly better than does the T1 GRE technique. PMID:28057964

  16. Non-enhanced MR angiography of renal artery using inflow-sensitive inversion recovery pulse sequence: a prospective comparison with enhanced CT angiography.

    PubMed

    Xu, Jun-ling; Shi, Da-Peng; Li, Yong-Li; Zhang, Ji-liang; Zhu, Shao-cheng; Shen, Hao

    2011-11-01

    To prospectively evaluate the diagnostic value of non-enhanced inflow-sensitive inversion recovery (IFIR) MR angiography for the detection of renal artery stenosis (RAS), with enhanced CT angiography performed as the reference standard. Sixty consecutive patients suspected of RAS underwent both of IFIR MR and enhanced CT angiography. Subjective image quality, renal artery depiction and renal artery grading were all evaluated on artery-by-artery basis. Spearman rank correlation analysis was used to assess agreement between the two techniques. The diagnostic sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for RAS detection at IFIR MR angiography were calculated. One hundred twenty-six main renal arteries were visualized on enhanced CT and non-enhanced MR angiographic images, respectively. The Spearman rank correlation was 0.773 (P<.001) for renal artery depiction, 0.998 (P<.001) for renal arteries grading and 0.833 (P<.001) for RAS detection between the two modalities. The sensitivity, specificity, PPV and NPV of IFIR MR angiography for RAS detection demonstrated 100%, 99.0%, 92.0% and 100%, respectively. Non-enhanced IFIR MR angiography had high sensitivity, specificity, PPV and NPV for RAS detection. It could be the first choice of renal artery imaging methods to avoid ionizing irradiation and renal toxicity from contrast media. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  17. Comparison of Maximum Signal Intensity of Contrast Agent on T1-Weighted Images Using Spin Echo, Fast Spin Echo and Inversion Recovery Sequences

    PubMed Central

    Nazarpoor, Mahmood; Poureisa, Masoud; Daghighi, Mohammad Hossein

    2012-01-01

    Background MRI is not able to directly measure the concentration of contrast agent. It is measured indirectly from the signal intensity (SI). It is very important to know how much contrast agent should be injected to receive a maximum SI in the region of interest (ROI). Objectives The aim of this study was to investigate the maximum relationship between contrast concentration and signal intensity (SI) on T1-weighted images using spin echo (SE), fast spin echo (FSE) and inversion recovery (IR) sequences. Materials and Methods To assess the relationship between SI and concentration, a water-filled phantom containing vials of different concentrations of gadolinium DTPA (Gd-DTPA) (0 to 19.77 mmol/L) or a constant concentration (1.2 mmol/L) of contrast agent was used. The vials of constant concentration were used to measure coil nonuniformity. The mean SI was obtained in the ROI using T1-weighted images. All studies were carried out using a 0.3 T clinical MR scanner with a standard head coil. Results This study shows that maximum SI will appear at different ranges in different sequences. The maximum SI can be seen at concentrations of 5.95, 4.96 and 3.98mmol/L for SE, FSE and IR, respectively. Conclusion Using standard imaging parameters, each MRI sequence reaches its maximum SI in a specific contrast concentration, which is highest in SE and least in IR in a comparison between SE, FSE and IR sequences. PMID:23599710

  18. A high resolution and high contrast MRI for differentiation of subcortical structures for DBS targeting: the Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR).

    PubMed

    Sudhyadhom, Atchar; Haq, Ihtsham U; Foote, Kelly D; Okun, Michael S; Bova, Frank J

    2009-08-01

    DBS depends on precise placement of the stimulating electrode into an appropriate target region. Image-based (direct) targeting has been limited by the ability of current technology to visualize DBS targets. We have recently developed and employed a Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR) 3T MRI sequence to more reliably visualize these structures. The FGATIR provides significantly better high resolution thin (1 mm) slice visualization of DBS targets than does either standard 3T T1 or T2-weighted imaging. The T1 subcortical image revealed relatively poor contrast among the targets for DBS, though the sequence did allow localization of striatum and thalamus. T2 FLAIR scans demonstrated better contrast between the STN, SNr, red nucleus (RN), and pallidum (GPe/GPi). The FGATIR scans allowed for localization of the thalamus, striatum, GPe/GPi, RN, and SNr and displayed sharper delineation of these structures. The FGATIR also revealed features not visible on other scan types: the internal lamina of the GPi, fiber bundles from the internal capsule piercing the striatum, and the boundaries of the STN. We hope that use of the FGATIR to aid initial targeting will translate in future studies to faster and more accurate procedures with consequent improvements in clinical outcomes.

  19. Potential of fluid-attenuated inversion recovery MRI as an alternative to contrast-enhanced MRI for oral and maxillofacial vascular malformations: experimental and clinical studies.

    PubMed

    Sasaki, Yoshinori; Sakamoto, Junichiro; Otonari-Yamamoto, Mika; Nishikawa, Keiichi; Sano, Tsukasa

    2013-10-01

    To determine the potential of fluid-attenuated inversion recovery (FLAIR) imaging of oral and maxillofacial vascular malformations as an alternative to contrast-enhanced magnetic resonance imaging (MRI), we investigated the influence of differences in T1 and T2 values on image contrast in FLAIR images and evaluated the diagnostic utility of such images. FLAIR imaging and heavily T2-weighted (hT2-weighted) imaging were performed using a phantom. FLAIR and hT2-weighted images of 32 lesions (11 mucous cysts, 12 vascular malformations, and 9 tumors) were also studied retrospectively. The contrast-to-noise ratios (CNRs) and CNR change ratios were compared. All aqueous solutions except those with a short T2 value were discriminated by CNR change ratio (P < .05). All 3 types of lesions were discriminated by CNR change ratio (P < .05). FLAIR imaging has potential as an alternative to contrast-enhanced MRI in differentiating vascular malformations from other types of lesions in the oral and maxillofacial region. Copyright © 2013 Elsevier Inc. All rights reserved.

  20. Fast perfusion measurements in rat skeletal muscle at rest and during exercise with single-voxel FAIR (flow-sensitive alternating inversion recovery).

    PubMed

    Pohmann, Rolf; Künnecke, Basil; Fingerle, Jürgen; von Kienlin, Markus

    2006-01-01

    Non-invasive measurement of perfusion in skeletal muscle by in vivo magnetic resonance remains a challenge due to its low level and the correspondingly low signal-to-noise ratio. To enable accurate, quantitative, and time-resolved perfusion measurements in the leg muscle, a technique with a high sensitivity is required. By combining a flow-sensitive alternating inversion recovery (FAIR)-sequence with a single-voxel readout, we have developed a new technique to measure the perfusion in the rat gastrocnemius muscle at rest, yielding an average value of 19.4 +/- 4.8 mL/100 g/min (n = 22). In additional experiments, perfusion changes were elicited by acute ischemia and reperfusion or by exercise induced by electrical, noninvasive muscle stimulation with varying duration and intensity. The perfusion time courses during these manipulations were measured with a temporal resolution of 2.2 min, showing increases in perfusion of a factor of up to 2.5. In a direct comparison, the results agreed closely with values found with microsphere measurements in the same animals. The quantitative and noninvasive method can significantly facilitate the investigation of atherosclerotic diseases and the examination of drug efficacy.

  1. Time course of arterial hyperintensity with fast fluid-attenuated inversion-recovery imaging in acute and subacute middle cerebral arterial infarction.

    PubMed

    Maeda, M; Koshimoto, Y; Uematsu, H; Yamada, H; Kimura, H; Kawamura, Y; Itoh, H; Sakuma, H; Takeda, K

    2001-06-01

    The purpose of this study was to evaluate the time course of arterial hyperintensity (AH) in acute and subacute cerebral infarctions of the middle cerebral artery (MCA) distribution by using fast fluid-attenuated inversion-recovery (FLAIR) imaging. A total of 40 FLAIR MR examinations were performed in 27 patients with MCA infarction within 13 days after ictus. Thirteen patients underwent two MR examinations during this period. Thrombotic or embolic infarctions were included in this study, but lacunar infarctions were excluded. The presence or absence of AH and the location of AH were analyzed. Overall, AH was found in 24 (60%) of 40 FLAIR examinations within 13 days after onset. AH was seen in 17 (100%) examinations less than 24 hours old, four (40%) of 10 examinations 1-4 days old, two (18%) of 11 examinations 5-9 days old, and one (50%) of two examinations 10-13 days old. AH was most frequently found at the sylvian fissure (87%), followed by the sulci (54%), and the horizontal segment of MCA (29%) in the affected MCA distribution. Although AH could be seen even at 13 days after ictus, the presence of AH declined over time. AH represented an early sign of acute embolic or thrombotic infarction. J. Magn. Reson. Imaging 2001;13:987-990. Copyright 2001 Wiley-Liss, Inc.

  2. Quantitative measurements of relative fluid-attenuated inversion recovery (FLAIR) signal intensities in acute stroke for the prediction of time from symptom onset

    PubMed Central

    Cheng, Bastian; Brinkmann, Mathias; Forkert, Nils D; Treszl, Andras; Ebinger, Martin; Köhrmann, Martin; Wu, Ona; Kang, Dong-Wha; Liebeskind, David S; Tourdias, Thomas; Singer, Oliver C; Christensen, Soren; Luby, Marie; Warach, Steven; Fiehler, Jens; Fiebach, Jochen B; Gerloff, Christian; Thomalla, Götz

    2013-01-01

    In acute stroke magnetic resonance imaging, a ‘mismatch' between visibility of an ischemic lesion on diffusion-weighted imaging (DWI) and missing corresponding parenchymal hyperintensities on fluid-attenuated inversion recovery (FLAIR) data sets was shown to identify patients with time from symptom onset ≤4.5 hours with high specificity. However, moderate sensitivity and suboptimal interpreter agreement are limitations of a visual rating of FLAIR lesion visibility. We tested refined image analysis methods in patients included in the previously published PREFLAIR study using refined visual analysis and quantitative measurements of relative FLAIR signal intensity (rSI) from a three-dimensional, segmented stroke lesion volume. A total of 399 patients were included. The rSI of FLAIR lesions showed a moderate correlation with time from symptom onset (r=0.382, P<0.001). A FLAIR rSI threshold of <1.0721 predicted symptom onset ≤4.5 hours with slightly increased specificity (0.85 versus 0.78) but also slightly decreased sensitivity (0.47 versus 0.58) as compared with visual analysis. Refined visual analysis differentiating between ‘subtle' and ‘obvious' FLAIR hyperintensities and classification and regression tree algorithms combining information from visual and quantitative analysis also did not improve diagnostic accuracy. Our results raise doubts whether the prediction of stroke onset time by visual image judgment can be improved by quantitative rSI measurements. PMID:23047272

  3. The leptomeningeal "ivy sign" on fluid-attenuated inversion recovery MR imaging in Moyamoya disease: a sign of decreased cerebral vascular reserve?

    PubMed

    Mori, N; Mugikura, S; Higano, S; Kaneta, T; Fujimura, M; Umetsu, A; Murata, T; Takahashi, S

    2009-05-01

    Moyamoya disease is an idiopathic occlusive cerebrovascular disorder with abnormal microvascular proliferation. We investigated the clinical utility of leptomeningeal high signal intensity (ivy sign) sometimes seen on fluid-attenuated inversion recovery images in Moyamoya disease. We examined the relationship between the degree of the ivy sign and the severity of the ischemic symptoms in 96 hemispheres of 48 patients with Moyamoya disease. We classified each cerebral hemisphere into 4 regions from anterior to posterior. In 192 regions of 24 patients, we examined the relationship between the degree of the ivy sign and findings of single-photon emission CT, including the resting cerebral blood flow (CBF) and cerebral vascular reserve (CVR). The degree of the ivy sign showed a significant positive relationship with the severity of the ischemic symptoms (P < .001). Of the 4 regions, the ivy sign was most frequently and prominently seen in the anterior part of the middle cerebral artery region. The degree of the ivy sign showed a negative relationship with the resting CBF (P < .0034) and a more prominent negative relationship with the CVR (P < .001). The leptomeningeal ivy sign indicates decreased CVR in Moyamoya disease.

  4. The Ivy Sign on Fluid Attenuated Inversion Recovery Images Related to Single-Photon Emission Computed Tomography Cerebral Blood Flow in Moyamoya Disease: A Case Report.

    PubMed

    Matano, Fumihiro; Murai, Yasuo; Kubota, Asami; Mizunari, Takayuki; Kobayashi, Shiro; Morita, Akio

    2017-01-17

    Moyamoya disease is an idiopathic progressive cerebrovascular steno-occlusive disorder characterized by the formation of numerous collaterals called moyamoya vessels. Accurate evaluation of vascular status and CBF is needed for prompt treatment to prevent ischemic and/or hemorrhagic events. The pathogenesis of the ivy sign on fluid attenuated inversion recovery (FLAIR) images of moyamoya disease patients is unclear. We report a moyamoya disease case wherein the ivy sign changed in relation to SPECT-measured CBF during progression and following treatment. A 49-year-old female presented with slight aphasia and right hemiparesis. MRI diffusion-weighted image revealed cerebral infarction in the left frontal lobe. Cerebral angiography images showed bilateral distal internal carotid artery stenosis and moyamoya vessels. FLAIR images exhibited the ivy sign. We performed superficial temporal artery-middle cerebral artery(STA-MCA) bypass surgery with encephalogaleosynangiosis(EGS) and encephalomyosynangiosis(EMS) on the left side 6 months after first presentation. After operation, left-side resting CBF gradually improved on SPECT and the ivy sign decreased. On the other hand, right-side CBF gradually deteriorated at rest, and the ivy sign increased. Therefore, we performed STA-MCA bypass with EGS and EMS on the right side 4 years after first presentation. After operation, resting CBF increased and ivy sign decreased. The FLAIR ivy sign may be a useful indicator of both deterioration and improvement of CBF status without the need for CBF imaging using contrast material.

  5. MR imaging of focal lung lesions: elimination of flow and motion artifact by breath-hold ECG-gated and black-blood techniques on T2-weighted turbo SE and STIR sequences.

    PubMed

    Yamashita, Y; Yokoyama, T; Tomiguchi, S; Takahashi, M; Ando, M

    1999-05-01

    Respiratory and cardiac motion correction may result in better turbo spin-echo (SE) imaging of the lung. To compare breath-hold cardiac-gated black-blood T2-weighted turbo SE and turbo short-inversion-time inversion-recovery (STIR) magnetic resonance (MR) imaging pulse sequences with conventional breath-hold turbo SE and half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences for lesion conspicuity of focal lung lesions, 42 patients with focal lung lesions were prospectively studied with MR imaging at 1.5 T. Helical computed tomography was used as a reference. In comparison with the conventional breath-hold turbo SE sequence, all black-blood sequences had fewer image artifacts arising from the heart and blood flow. The overall image quality for the black-blood turbo SE and turbo STIR sequences was superior to that for the breath-hold turbo SE and HASTE sequence (P < 0.01). Not only focal lung lesions but also surrounding inflammatory changes were clearly visualized with these two sequences. With the HASTE sequence, although several slices could be obtained in one breath-hold, both the tumor and vessels appeared blurred. We conclude that T2-weighted turbo SE and turbo STIR imaging of the lung with effective suppression of flow and motion artifacts provide high-quality images in patients with focal lung lesions.

  6. Lipid suppression via double inversion recovery with symmetric frequency sweep for robust 2D‐GRAPPA‐accelerated MRSI of the brain at 7 T

    PubMed Central

    Hangel, Gilbert; Strasser, Bernhard; Považan, Michal; Gruber, Stephan; Chmelík, Marek; Gajdošík, Martin; Trattnig, Siegfried

    2015-01-01

    This work presents a new approach for high‐resolution MRSI of the brain at 7 T in clinically feasible measurement times. Two major problems of MRSI are the long scan times for large matrix sizes and the possible spectral contamination by the transcranial lipid signal. We propose a combination of free induction decay (FID)‐MRSI with a short acquisition delay and acceleration via in‐plane two‐dimensional generalised autocalibrating partially parallel acquisition (2D‐GRAPPA) with adiabatic double inversion recovery (IR)‐based lipid suppression to allow robust high‐resolution MRSI. We performed Bloch simulations to evaluate the magnetisation pathways of lipids and metabolites, and compared the results with phantom measurements. Acceleration factors in the range 2–25 were tested in a phantom. Five volunteers were scanned to verify the value of our MRSI method in vivo. GRAPPA artefacts that cause fold‐in of transcranial lipids were suppressed via double IR, with a non‐selective symmetric frequency sweep. The use of long, low‐power inversion pulses (100 ms) reduced specific absorption rate requirements. The symmetric frequency sweep over both pulses provided good lipid suppression (>90%), in addition to a reduced loss in metabolite signal‐to‐noise ratio (SNR), compared with conventional IR suppression (52–70%). The metabolic mapping over the whole brain slice was not limited to a rectangular region of interest. 2D‐GRAPPA provided acceleration up to a factor of nine for in vivo FID‐MRSI without a substantial increase in g‐factors (<1.1). A 64 × 64 matrix can be acquired with a common repetition time of ~1.3 s in only 8 min without lipid artefacts caused by acceleration. Overall, we present a fast and robust MRSI method, using combined double IR fat suppression and 2D‐GRAPPA acceleration, which may be used in (pre)clinical studies of the brain at 7 T. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd

  7. In-season changes in heart rate recovery are inversely related to time to exhaustion but not aerobic capacity in rowers.

    PubMed

    Haraldsdottir, K; Brickson, S; Sanfilippo, J; Dunn, W; Watson, A

    2017-06-26

    To determine if in-season changes in heart rate recovery (HRR) are related to aerobic fitness and performance in collegiate rowers. Twenty-two female collegiate rowers completed testing before and after their competitive season. Body fat percentage (BF%) was determined by dual-energy X-ray absorptiometry. Maximal aerobic capacity (VO2max ) and time to exhaustion (Tmax ) were determined during maximal rowing ergometer testing followed by 1 minute of recovery. HRR was expressed absolutely and as a percentage of maximal HR (HRR%1 min ). Variables were compared using paired Wilcoxon tests. Multivariable regression models were used to predict in-season changes in HRR using changes in VO2max and Tmax , while accounting for changes in BF%. From preseason to post-season, VO2max and BF% decreased (3.98±0.42 vs 3.78±0.35 L/min, P=.002 and 23.8±3.4 vs 21.3±3.9%, P<.001, respectively), while Tmax increased (11.7±1.3 vs 12.6±1.3 min, P=.002), and HRR%1 min increased (11.1±2.7 vs 13.8±3.8, P=.001). In-season changes in VO2max were not associated with HRR%1 min (P>.05). In-season changes in Tmax were related to changes in HRR%1 min (β=-1.67, P=.006). In-season changes in BF% were not related to changes in HRR (P>.05 for all). HRR1 min and HRR%1 min were faster preseason to post-season, although the changes were unrelated to VO2max . Faster HRR%1 min post-season was inversely related to changes in Tmax . This suggests that HRR should not be used as a measure of aerobic capacity in collegiate rowers, but is a promising measure of training status in this population. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. [Study of optimal flip angle for inversion-recovery gradient echo method in delayed contrast-enhanced cardiac magnetic resonance imaging].

    PubMed

    Ogawa, Masashi; Matsumura, Yoshio; Tsuchihashi, Toshio

    2013-04-01

    Delayed contrast-enhanced cardiac magnetic resonance imaging (MRI) is a valuable tool for detecting myocardial infarction and assessing myocardial viability. The standard viability MRI technique is the inversion-recovery gradient echo (IR-GRE) method. Several previous studies have demonstrated that this imaging technique provides superior image quality at high magnetic field strengths, e.g., 3.0 T. However, there are numerous possible flip angles. We investigated the optimal flip angle of IR-GRE in delayed contrast-enhanced cardiac MRI. Phantoms were made that modeled infarcted myocardium and normal myocardium after administration of contrast agent. To determine optimal flip angle, we compared the contrast-to-noise ratio (CNR) among these phantoms and evaluated the degree of artifacts induced by increased flip angle. The flip angle that showed the highest CNR for 2D IR-GRE and 3D IR-GRE was 30°/15° at 1.5 T and 25°/15° at 3.0 T. The flip angle that showed the highest CNR was independent of R-R interval. Streak artifacts induced by increased flip angle tended to occur more readily at 3.0 T than 1.5 T. The optimal flip angle for 2D IR-GRE and 3D IR-GRE at 1.5 T was 30° and 15°, respectively. At 3.0 T, taking into account the results for both CNR and streak artifacts, we concluded the optimal flip angle of 2D IR-GRE to be 15-20°.

  9. 2D phase-sensitive inversion recovery imaging to measure in vivo spinal cord gray and white matter areas in clinically feasible acquisition times.

    PubMed

    Papinutto, Nico; Schlaeger, Regina; Panara, Valentina; Caverzasi, Eduardo; Ahn, Sinyeob; Johnson, Kevin J; Zhu, Alyssa H; Stern, William A; Laub, Gerhard; Hauser, Stephen L; Henry, Roland G

    2015-09-01

    To present and assess a procedure for measurement of spinal cord total cross-sectional areas (TCA) and gray matter (GM) areas based on phase-sensitive inversion recovery imaging (PSIR). In vivo assessment of spinal cord GM and white matter (WM) could become pivotal to study various neurological diseases, but it is challenging because of insufficient GM/WM contrast provided by conventional magnetic resonance imaging (MRI). We acquired 2D PSIR images at 3T at each disc level of the spinal axis in 10 healthy subjects and measured TCA, cord diameters, WM and GM areas, and GM area/TCA ratios. Second, we investigated 32 healthy subjects at four selected levels (C2-C3, C3-C4, T8-T9, T9-T10, total acquisition time <8 min) and generated normative reference values of TCA and GM areas. We assessed test-retest, intra- and interoperator reliability of the acquisition strategy, and measurement steps. The measurement procedure based on 2D PSIR imaging allowed TCA and GM area assessments along the entire spinal cord axis. The tests we performed revealed high test-retest/intraoperator reliability (mean coefficient of variation [COV] at C2-C3: TCA = 0.41%, GM area = 2.75%) and interoperator reliability of the measurements (mean COV on the 4 levels: TCA = 0.44%, GM area = 4.20%; mean intraclass correlation coefficient: TCA = 0.998, GM area = 0.906). 2D PSIR allows reliable in vivo assessment of spinal cord TCA, GM, and WM areas in clinically feasible acquisition times. The area measurements presented here are in agreement with previous MRI and postmortem studies. © 2014 Wiley Periodicals, Inc.

  10. Sensory neuronopathy involves the spinal cord and brachial plexus: a quantitative study employing multiple-echo data image combination (MEDIC) and turbo inversion recovery magnitude (TIRM).

    PubMed

    Bao, Yi-Fang; Tang, Wei-Jun; Zhu, Dong-Qing; Li, Yu-Xin; Zee, Chi-Shing; Chen, Xiang-Jun; Geng, Dao-Ying

    2013-01-01

    Sensory neuronopathy (SNN) is a distinctive subtype of peripheral neuropathies, specifically targeting dorsal root ganglion (DRG). We utilized MRI to demonstrate the imaging characteristics of DRG, spinal cord (SC), and brachial plexus at C7 level in SNN. We attempted multiple-echo data image combination (MEDIC) and turbo inversion recovery magnitude (TIRM) methods in nine patients with sensory neuronopathy and compared with those in 16 disease controls and 20 healthy volunteers. All participants underwent MRI for the measurement of DRG, posterior column (PC), lateral column, and spinal cord area (SCA) at C7 level. DRG diameters were obtained through its largest cross section, standardized by dividing sagittal diameter of mid-C7 vertebral canal. We also made comparisons of standardized anteroposterior diameter (APD) and left-right diameters of SC and PC in these groups. Signal intensity and diameter of C7 spinal nerve were assessed on TIRM. Compared to control groups, signal intensities of DRG and PC were higher in SNN patients when using MEDIC, but the standardized diameters were shorter in either DRG or PC. Abnormal PC signal intensities were identified in eight out of nine SNN patients (89 %) with MEDIC and five out of nine (56 %) with T2-weighted images. SCA, assessed with MEDIC, was smaller in SNN patients than in the other groups, with significant reduction of its standardized APD. C7 nerve root diameters, assessed with TIRM, were decreased in SNN patients. MEDIC and TIRM sequences demonstrate increased signal intensities and decreased area of DRG and PC, and decreased diameter of nerve roots in patients with SNN, which can play a significant role in early diagnosis.

  11. Diffusion-weighted imaging-fluid-attenuated inversion recovery mismatch is associated with better neurologic response to intravenous thrombolytic therapy in acute ischemic stroke patients.

    PubMed

    Jeong, Jong Yeong; Han, Sang Kuk; Shin, Dong Hyuk; Na, Ji Ung; Lee, Hyun Jung; Choi, Pil Cho; Lee, Jeong Hun

    2015-03-01

    To investigate differences in the effect of intravenous (IV) thrombolysis regarding the mismatch of diffusion-weighted imaging-fluid-attenuated inversion recovery (DWI-FLAIR) among acute ischemic stroke patients who visited the emergency department (ED) within 3 hours from the onset of symptoms. Among ED patients presenting with an acute ischemic stroke between January 2011 and May 2013 at a tertiary hospital, those who underwent magnetic resonance imaging before IV thrombolytic therapy were included in this retrospective study. Patients were divided into DWI-FLAIR mismatch and match groups. National Institutes of Health Stroke Scale (NIHSS) scores obtained initially, 24 hours after thrombolytic therapy, and on discharge, and early neurologic improvement (ENI) and major neurologic improvement (MNI) were compared. During the study period, 50 of the 213 acute ischemic stroke patients who presented to the ED were included. The DWI-FLAIR mismatch group showed a statistically significantly greater reduction in NIHSS both at 24 hours after thrombolytic therapy and upon discharge than did the match group (5.5 vs. 1.2, P<0.001; 6.0 vs. 2.3, P<0.01, respectively). Moreover, ENI and MNI were significantly greater for the DWI-FLAIR mismatch group than for the match group (27/36 vs. 2/14, P<0.001; 12/36 vs. 0/14, P=0.012, respectively). Among acute ischemic stroke patients who visited the ED within 3 hours from the onset of symptoms, patients who showed DWI-FLAIR mismatch showed a significantly better response to IV thrombolytic therapy than did the DWI-FLAIR match group in terms of neurologic outcome.

  12. Accuracy for detection of simulated lesions: comparison of fluid-attenuated inversion-recovery, proton density--weighted, and T2-weighted synthetic brain MR imaging

    NASA Technical Reports Server (NTRS)

    Herskovits, E. H.; Itoh, R.; Melhem, E. R.

    2001-01-01

    OBJECTIVE: The objective of our study was to determine the effects of MR sequence (fluid-attenuated inversion-recovery [FLAIR], proton density--weighted, and T2-weighted) and of lesion location on sensitivity and specificity of lesion detection. MATERIALS AND METHODS: We generated FLAIR, proton density-weighted, and T2-weighted brain images with 3-mm lesions using published parameters for acute multiple sclerosis plaques. Each image contained from zero to five lesions that were distributed among cortical-subcortical, periventricular, and deep white matter regions; on either side; and anterior or posterior in position. We presented images of 540 lesions, distributed among 2592 image regions, to six neuroradiologists. We constructed a contingency table for image regions with lesions and another for image regions without lesions (normal). Each table included the following: the reviewer's number (1--6); the MR sequence; the side, position, and region of the lesion; and the reviewer's response (lesion present or absent [normal]). We performed chi-square and log-linear analyses. RESULTS: The FLAIR sequence yielded the highest true-positive rates (p < 0.001) and the highest true-negative rates (p < 0.001). Regions also differed in reviewers' true-positive rates (p < 0.001) and true-negative rates (p = 0.002). The true-positive rate model generated by log-linear analysis contained an additional sequence-location interaction. The true-negative rate model generated by log-linear analysis confirmed these associations, but no higher order interactions were added. CONCLUSION: We developed software with which we can generate brain images of a wide range of pulse sequences and that allows us to specify the location, size, shape, and intrinsic characteristics of simulated lesions. We found that the use of FLAIR sequences increases detection accuracy for cortical-subcortical and periventricular lesions over that associated with proton density- and T2-weighted sequences.

  13. Assessment of left ventricular myocardial scar in infiltrative and non-ischemic cardiac diseases by free breathing three dimensional phase sensitive inversion recovery (PSIR) TurboFLASH.

    PubMed

    Kino, Aya; Keeling, Aoife N; Farrelly, Cormac T; Sheehan, John J; Davarpanah, Amir H; Weele, Peter J; Zuehldorff, Sven; Carr, James C

    2011-04-01

    The purpose of this study was to compare a navigator gated free breathing 3D Phase Sensitive Inversion Recovery (PSIR) TurboFLASH to an established 2D PSIR TurboFLASH method for detecting myocardial late gadolinium hyperenhanced lesions caused by infiltrative and non-ischemic cardiomyopathy. Under an IRB approved protocol; patients with suspected non-ischemic infiltrative myocardial heart disease were examined on a 1.5T MR scanner for late enhancement after the administration of gadolinium using a segmented 2D PSIR TurboFLASH sequence followed by a navigator-gated 3D PSIR TurboFLASH sequence. Two independent readers analyzed image quality using a four point Likert scale for qualitative analysis (0 = poor, non diagnostic; 1 = fair, diagnostic may be impaired; 2 = good, some artifacts but not interfering in diagnostics, 3 = excellent, no artifacts) and also reported presence or absence of scar. Detected scars were classified based on area and location and also compared quantitatively in volume. Twenty-seven patients were scanned using both protocols. Image quality score did not differ significantly (p = 0.358, Wilcoxon signed rank test) for both technique. Scars were detected in 24 patients. Larger numbers of hyperenhanced scars were detected with 3D PSIR (200) compared to 2D PSIR (167) and scar volume were significant larger in 3D PSIR (p = 0.004). The mean scar volume over all cases was 49.95 cm(3) for 2D PSIR and 70.02 cm(3) for 3D PSIR. The navigator gated free breathing 3D PSIR approach is a suitable method for detecting myocardial late gadolinium hyperenhanced lesions caused by non-ischemic cardiomyopathy due to its complete isotropic coverage of the left ventricle, improving detection of scar lesions compared to 2D PSIR imaging.

  14. Simultaneous acquisition of high-contrast and quantitative liver T1 images using 3D phase-sensitive inversion recovery: a feasibility study.

    PubMed

    Fujiwara, Yasuhiro; Maruyama, Hirotoshi; Kosaka, Nobuyuki; Ishimori, Yoshiyuki

    2017-08-01

    Background Tumor-to-liver contrast is low in images of chronically diseased livers because gadolinium-based hepatocyte-specific contrast agents (Gd-EOB-DTPA) accumulate less to hepatocytes. Purpose To determine whether phase-sensitive inversion recovery (PSIR) could improve the T1 contrasts of Gd-based contrast agents and liver parenchyma and simultaneously provide accurate T1 values for abdominal organs. Material and Methods The image contrasts of phantoms with different Gd concentrations that were obtained using PSIR were compared to conventional turbo field echo (TFE) results. T1 value was estimated using PSIR by performing iterations to investigate the two IR magnetization evolutions. The estimated T1 values were validated using IR-spin echo (IR-SE) and Look-Locker (L-L) sequences. In an in vivo study, the liver-to-spleen and liver-to-muscle contrasts of the PSIR and TFE images of seven volunteers were compared, as were the T1 values of liver parenchyma, spleen, and muscle obtained using PSIR and L-L sequences. Results The PSIR images showed T1 contrasts higher than those in the TFE results. The PSIR and IR-SE T1 values were linearly correlated. Additionally, the R1 estimated using PSIR were correlated with those measured using IR-SE and L-L. In the in vivo study, the liver-to-spleen and liver-to-muscle contrasts of PSIR were significantly higher than those obtained using TFE. T1 values of abdominal organs obtained using PSIR and L-L were clearly correlated. Conclusion PSIR may be capable of improving liver image T1 contrasts when Gd-based contrast agents are employed and simultaneously yielding accurate T1 values of abdominal organs.

  15. Localisation of the central sulcus region in glioma patients with three-dimensional fluid-attenuated inversion recovery and volume rendering: comparison with functional and conventional magnetic resonance.

    PubMed

    Willemse, Ronald B; Pouwels, Petra J W; Barkhof, Frederik; Vandertop, W Peter

    2011-04-01

    Volume rendering (VR) of three-dimensional (3D) fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images shows regional intensity differences, reflecting the central sulcus (CS) region and occipital cortex. The purpose of this study was to determine whether 3D FLAIR with VR could be used as an alternative method to localise the CS region in comparison with functional and conventional MR-imaging in patients with perirolandic glioma. Eleven patients with intracranial gliomas were studied with single-slab 3D FLAIR including VR and conventional T1-weighted imaging. In all patients, preoperative functional magnetic resonance imaging (fMRI) was performed with a motor paradigm of the hand. The hypo-intense central gyri on 3D FLAIR with VR were interpreted as the CS area. Localisation of the motor hand knob on anatomical images and fMRI results were used for identification of the primary motor cortex. Anatomical localisation of the motor hand knob on T1-weighted images was possible in 91% of both hemispheres. In 73% of the affected hemispheres (AH) and 91% of the unaffected hemispheres (UH) the hand knob and CS region could be identified on 3D FLAIR axial and VR images, respectively. With one exception, fMRI activation confirmed the CS region as observed with 3D FLAIR with VR. Volume rendering of 3D FLAIR MR images shows central hypo-intensities frequently corresponding with the CS region. Two-dimensional localisation of the CS region on conventional T1-weighted images and fMRI seems favourable compared to 3D FLAIR. However, in selected cases, especially where fMRI is not possible or feasible, volume rendering with 3D FLAIR may enhance the 3D visualisation of gliomas in relation to the CS region which can be used as an alternative method in the presurgical structural and functional evaluation of neurosurgical patients.

  16. [Three-dimensional fluid attenuated inversion recovery imaging at 3T MRI in sudden deafness: its findings and relationship with the prognosis].

    PubMed

    Qian, Yin-feng; Wu, Ji-chun; Zhang, Cheng; Yu, Yong-qiang

    2011-10-01

    To investigate inner ear of patients with sudden deafness with three-dimensional fluid attenuated inversion recovery (3D FLAIR) MRI, and the relationship between the results of 3D FLAIR and the prognosis. Twenty-three patients with sudden deafness received 3D FLAIR at 3T MRI, and the signals of inner ear were recorded. Hearing levels were evaluated at initial visit and after treatment. The relationship between 3D FLAIR findings and hearing prognosis was evaluated. Eight patients with sudden deafness showed high signals in the affected cochlea on 3D FLAIR, the others of affected cochlea and all of contralateral cochlea showed no signal on 3D FLAIR. The age, sex, affected side, period to initial visit and initial audiogram had no difference between cochlea no signal group and high signal group. The average auditory threshold (x±s) in cochlea high signal group (90±21) dB HL was significant higher than that in cochlea no signal group (60±28) dB HL, P<0.05 at patients' discharge. After treatment, in cochlea no signal group, two cases' hearing was complete recovered, remarkable improvement in five cases, slight improvement in two cases and no change in six cases. In cochlea high signal group, hearing was slight improvement in one case and no change in seven cases. The prognosis was significant difference between two groups. Five of seven patients with vertigo and sudden deafness showed high signal in affected side vestibule on 3D FLAIR, and the hearing of whom had no change after treatment. 3D FLAIR can show high signal in affected inner ear in sudden deafness patients, and which is related to a poor hearing prognosis.

  17. Unilateral hemispheric proliferation of ivy sign on fluid-attenuated inversion recovery images in moyamoya disease correlates highly with ipsilateral hemispheric decrease of cerebrovascular reserve.

    PubMed

    Kawashima, M; Noguchi, T; Takase, Y; Ootsuka, T; Kido, N; Matsushima, T

    2009-10-01

    An ivy sign is considered to represent diffuse leptomeningeal collaterals found on fluid-attenuated inversion recovery (FLAIR) images of patients with Moyamoya disease. We evaluated the correlation between unilateral ivy proliferation in a hemisphere and cerebrovascular hemodynamic status to learn the clinical significance of the ivy sign. A total of 35 patients with Moyamoya disease were included. Correlation between ivy dominance on FLAIR images and hemodynamic status with use of iodine 123 N-isopropyl-p-iodoamphetamine ((123)I-IMP) single-photon emission CT (SPECT) was evaluated. Distributional differences of ivy signs between both hemispheres were observed in 22 (64.7%) of 34 patients with a positive ivy sign, all of whom showed decreased vascular reserve/reactivity in the ivy-dominant hemisphere (IDH). The proportion of the stage II (misery perfusion) area to IDH was higher than that in the ivy less-dominant hemisphere (ILDH) in the quantitative analysis. The mean vascular reserve was lower in IDH than ILDH. There were 15 of 22 patients who had bypass surgery on IDH because of transient ischemic attack from ischemia of IDH. Patients with symmetric ivy distributions showed a variety of hemodynamic status. MR angiography (MRA) stage of IDH (2.95 +/- 0.39) was higher compared with ILDH (2.60 +/- 0.50; P < .05). Regional arteriocapillary circulation time ratio in IDH was longer compared with ILDH (P < .05). Ivy proliferation decreased in 10 (55.6%) of 18 patients who underwent bypass surgery during the follow-up period. Unilateral hemispheric ivy proliferation correlated highly with the existence of an ipsilateral decreased vascular reserve associated with the development of leptomeningeal collaterals in patients with Moyamoya disease.

  18. Accuracy for detection of simulated lesions: comparison of fluid-attenuated inversion-recovery, proton density--weighted, and T2-weighted synthetic brain MR imaging

    NASA Technical Reports Server (NTRS)

    Herskovits, E. H.; Itoh, R.; Melhem, E. R.

    2001-01-01

    OBJECTIVE: The objective of our study was to determine the effects of MR sequence (fluid-attenuated inversion-recovery [FLAIR], proton density--weighted, and T2-weighted) and of lesion location on sensitivity and specificity of lesion detection. MATERIALS AND METHODS: We generated FLAIR, proton density-weighted, and T2-weighted brain images with 3-mm lesions using published parameters for acute multiple sclerosis plaques. Each image contained from zero to five lesions that were distributed among cortical-subcortical, periventricular, and deep white matter regions; on either side; and anterior or posterior in position. We presented images of 540 lesions, distributed among 2592 image regions, to six neuroradiologists. We constructed a contingency table for image regions with lesions and another for image regions without lesions (normal). Each table included the following: the reviewer's number (1--6); the MR sequence; the side, position, and region of the lesion; and the reviewer's response (lesion present or absent [normal]). We performed chi-square and log-linear analyses. RESULTS: The FLAIR sequence yielded the highest true-positive rates (p < 0.001) and the highest true-negative rates (p < 0.001). Regions also differed in reviewers' true-positive rates (p < 0.001) and true-negative rates (p = 0.002). The true-positive rate model generated by log-linear analysis contained an additional sequence-location interaction. The true-negative rate model generated by log-linear analysis confirmed these associations, but no higher order interactions were added. CONCLUSION: We developed software with which we can generate brain images of a wide range of pulse sequences and that allows us to specify the location, size, shape, and intrinsic characteristics of simulated lesions. We found that the use of FLAIR sequences increases detection accuracy for cortical-subcortical and periventricular lesions over that associated with proton density- and T2-weighted sequences.

  19. Evaluation of focus laterality in temporal lobe epilepsy: a quantitative study comparing double inversion-recovery MR imaging at 3T with FDG-PET.

    PubMed

    Morimoto, Emiko; Okada, Tomohisa; Kanagaki, Mitsunori; Yamamoto, Akira; Fushimi, Yasutaka; Matsumoto, Riki; Takaya, Shigetoshi; Ikeda, Akio; Kunieda, Takeharu; Kikuchi, Takayuki; Paul, Dominik; Miyamoto, Susumu; Takahashi, Ryosuke; Togashi, Kaori

    2013-12-01

    To quantitatively compare the diagnostic capability of double inversion-recovery (DIR) with F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for detection of seizure focus laterality in temporal lobe epilepsy (TLE). This study was approved by the institutional review board, and written informed consent was obtained. Fifteen patients with TLE and 38 healthy volunteers were enrolled. All magnetic resonance (MR) images were acquired using a 3T-MRI system. Voxel-based analysis (VBA) was conducted for FDG-PET images and white matter segments of DIR images (DIR-WM) focused on the whole temporal lobe (TL) and the anterior part of the temporal lobe (ATL). Distribution of hypometabolic areas on FDG-PET and increased signal intensity areas on DIR-WM were evaluated, and their laterality was compared with clinically determined seizure focus laterality. Correct diagnostic rates of laterality were evaluated, and agreement between DIR-WM and FDG-PET was assessed using κ statistics. Increased signal intensity areas on DIR-WM were located at the vicinity of the hypometabolic areas on FDG-PET, especially in the ATL. Correct diagnostic rates of seizure focus laterality for DIR-WM (0.80 and 0.67 for the TL and the ATL, respectively) were slightly higher than those for FDG-PET (0.67 and 0.60 for the TL and the ATL, respectively). Agreement of laterality between DIR-WM and FDG-PET was substantial for the TL and almost perfect for the ATL (κ = 0.67 and 0.86, respectively). High agreement in localization between DIR-WM and FDG-PET and nearly equivalent detectability of them show us an additional role of MRI in TLE. Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.

  20. Postprandial changes in secretory flow of pancreatic juice in the main pancreatic duct: evaluation with cine-dynamic MRCP with a spatially selective inversion-recovery (IR) pulse.

    PubMed

    Yasokawa, Kazuya; Ito, Katsuyoshi; Tamada, Tsutomu; Yamamoto, Akira; Hayashida, Minoru; Torigoe, Teruyuki; Tanimoto, Daigo; Higaki, Atsushi; Noda, Yasufumi; Kido, Ayumu

    2016-12-01

    To evaluate the influence of oral ingestion on the secretory flow dynamics of physiological pancreatic juice within the main pancreatic duct in healthy subjects by using cine-dynamic MRCP with spatially-selective inversion-recovery (IR) pulse non-invasively. Thirty-eight healthy subjects were investigated. MRCP with spatially-selective IR pulse was repeated every 15 s for 5 min to acquire a total of 20 images (cine-dynamic MRCP). A set of 20 MRCP images was repeatedly obtained before and after liquid oral ingestion every 7 min (including 2-min interval) for 40 min (a total of seven sets). Secretion grade of pancreatic juice on cine-dynamic MRCP was compared before and after oral ingestion using the nonparametric Wilcoxon signed-rank test. Median secretion grades of pancreatic juice at 5 min (score = 2.15), 12 min (score = 1.95) and 19 min (score = 2.05) after ingestion were significantly higher than that before ingestion (score = 1.40) (P = 0.004, P = 0.032, P = 0.045, respectively). Secretion grade of pancreatic juice showed a maximum peak of 2.15 at 5 min after ingestion. Thereafter, the secretion grade of pancreatic juice tended to gradually decline. Non-invasive cine-dynamic MRCP using spatially-selective IR pulse showed potential for evaluating postprandial changes in the secretory flow dynamics of pancreatic juice as a physiological reaction. • Secretion grade of pancreatic juice at cine-dynamic MRCP after ingestion was evaluated. • Secretion grade was significantly increased within 19 min after liquid meal ingestion. • Secretion grade showed maximum peak of 2.15 at 5 min after ingestion. • Postprandial changes in pancreatic juice flow can be assessed by cine-dynamic MRCP.

  1. Regional Fluid-Attenuated Inversion Recovery (FLAIR) at 7 Tesla correlates with amyloid beta in hippocampus and brainstem of cognitively normal elderly subjects

    PubMed Central

    Schreiner, Simon J.; Liu, Xinyang; Gietl, Anton F.; Wyss, Michael; Steininger, Stefanie C.; Gruber, Esmeralda; Treyer, Valerie; Meier, Irene B.; Kälin, Andrea M.; Leh, Sandra E.; Buck, Alfred; Nitsch, Roger M.; Pruessmann, Klaas P.; Hock, Christoph; Unschuld, Paul G.

    2014-01-01

    Background: Accumulation of amyloid beta (Aβ) may occur during healthy aging and is a risk factor for Alzheimer Disease (AD). While individual Aβ-accumulation can be measured non-invasively using Pittsburgh Compund-B positron emission tomography (PiB-PET), Fluid-attenuated inversion recovery (FLAIR) is a Magnetic Resonance Imaging (MRI) sequence, capable of indicating heterogeneous age-related brain pathologies associated with tissue-edema. In the current study cognitively normal elderly subjects were investigated for regional correlation of PiB- and FLAIR intensity. Methods: Fourteen healthy elderly subjects without known history of cognitive impairment received 11C-PiB-PET for estimation of regional Aβ-load. In addition, whole brain T1-MPRAGE and FLAIR-MRI sequences were acquired at high field strength of 7 Tesla (7T). Volume-normalized intensities of brain regions were assessed by applying an automated subcortical segmentation algorithm for spatial definition of brain structures. Statistical dependence between FLAIR- and PiB-PET intensities was tested using Spearman's rank correlation coefficient (rho), followed by Holm–Bonferroni correction for multiple testing. Results: Neuropsychological testing revealed normal cognitive performance levels in all participants. Mean regional PiB-PET and FLAIR intensities were normally distributed and independent. Significant correlation between volume-normalized PiB-PET signals and FLAIR intensities resulted for Hippocampus (right: rho = 0.86; left: rho = 0.84), Brainstem (rho = 0.85) and left Basal Ganglia vessel region (rho = 0.82). Conclusions: Our finding of a significant relationship between PiB- and FLAIR intensity mainly observable in the Hippocampus and Brainstem, indicates regional Aβ associated tissue-edema in cognitively normal elderly subjects. Further studies including clinical populations are necessary to clarify the relevance of our findings for estimating individual risk for age-related neurodegenerative

  2. Multicentre multiobserver study of diffusion-weighted and fluid-attenuated inversion recovery MRI for the diagnosis of sporadic Creutzfeldt-Jakob disease: a reliability and agreement study.

    PubMed

    Fujita, Koji; Harada, Masafumi; Sasaki, Makoto; Yuasa, Tatsuhiko; Sakai, Kenji; Hamaguchi, Tsuyoshi; Sanjo, Nobuo; Shiga, Yusei; Satoh, Katsuya; Atarashi, Ryuichiro; Shirabe, Susumu; Nagata, Ken; Maeda, Tetsuya; Murayama, Shigeo; Izumi, Yuishin; Kaji, Ryuji; Yamada, Masahito; Mizusawa, Hidehiro

    2012-01-01

    Objectives To assess the utility of the display standardisation of diffusion-weighted MRI (DWI) and to compare the effectiveness of DWI and fluid-attenuated inversion recovery (FLAIR) MRI for the diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD). Design A reliability and agreement study. Setting Thirteen MRI observers comprising eight neurologists and five radiologists at two universities in Japan. Participants Data of 1.5-Tesla DWI and FLAIR were obtained from 29 patients with sCJD and 13 controls. Outcome measures Standardisation of DWI display was performed utilising b0 imaging. The observers participated in standardised DWI, variable DWI (the display adjustment was observer dependent) and FLAIR sessions. The observers independently assessed each MRI for CJD-related lesions, that is, hyperintensity in the cerebral cortex or striatum, using a continuous rating scale. Performance was evaluated by the area under the receiver operating characteristics curve (AUC). Results The mean AUC values were 0.84 (95% CI 0.81 to 0.87) for standardised DWI, 0.85 (95% CI 0.82 to 0.88) for variable DWI and 0.68 (95% CI 0.63 to 0.72) for FLAIR, demonstrating the superiority of DWI (p<0.05). There was a trend for higher intraclass correlations of standardised DWI (0.74, 95% CI 0.66 to 0.83) and variable DWI (0.72, 95% CI 0.62 to 0.81) than that of FLAIR (0.63, 95% CI 0.53 to 0.74), although the differences were not statistically significant. Conclusions Standardised DWI is as reliable as variable DWI, and the two DWI displays are superior to FLAIR for the diagnosis of sCJD. The authors propose that hyperintensity in the cerebral cortex or striatum on 1.5-Tesla DWI but not FLAIR can be a reliable diagnostic marker for sCJD.

  3. Melt Stirring by Horizontal Crucible Vibration

    NASA Technical Reports Server (NTRS)

    Wolf, M. F.; Elwell, D.; Feigelson, R. S.

    1985-01-01

    Horizontal vibration suggested as technique for more effective stirring of melts in crystal-growth apparatus. Vibrational technique may replace accelerated crucible rotation. Potential superiority of vibrational technique shown by preliminary experiments in which ink stirred into water.

  4. A Chaotic Stirring by an Oscillating Point Vortex

    NASA Astrophysics Data System (ADS)

    Suh, Yong Kweon

    1991-03-01

    Aref’s blinking vortex system (H. Aref: J. Fluid Mech. 143 (1984) 1.) is extended to the case when the vortex oscillates harmonically. The equations of motion of the passive particle are given in coordinates suitable for integration. Stirring mechanism could be described by the horse-shoe map in the rotational way not in the linear way. The optimal operating condition for the best stirring exists for the parameter μ (proportional to the vortex strength, the period of the vortex motion and the inverse of the tank area). Merging and splitting between the chaotic regions takes place abruptly near the boundary when the parameters are changed and is responsible for the abrupt change in the chaotic area. The present system gives on the whole the chaotic region smaller than the original system.

  5. Deformation During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    White, Henry J.

    2002-01-01

    Friction Stir Welding (FSW) is a solid state welding process that exhibits characteristics similar to traditional metal cutting processes. The plastic deformation that occurs during friction stir welding is due to the superposition of three flow fields: a primary rotation of a radially symmetric solid plug of metal surrounding the pin tool, a secondary uniform translation, and a tertiary ring vortex flow (smoke rings) surrounding the tool. If the metal sticks to the tool, the plug surface extends down into the metal from the outer edge of the tool shoulder, decreases in diameter like a funnel, and closes up beneath the pin. Since its invention, ten years have gone by and still very little is known about the physics of the friction stir welding process. In this experiment, an H13 steel weld tool (shoulder diameter, 0.797 in; pin diameter, 0.312 in; and pin length, 0.2506 in) was used to weld three 0.255 in thick plates. The deformation behavior during friction stir welding was investigated by metallographically preparing a plan view sections of the weldment and taking Vickers hardness test in the key-hole region.

  6. Reliability of cortical lesion detection on double inversion recovery MRI applying the MAGNIMS-Criteria in multiple sclerosis patients within a 16-months period

    PubMed Central

    Thaler, Christian; Ceyrowski, Tim; Broocks, Gabriel; Treffler, Natascha; Sedlacik, Jan; Stürner, Klarissa; Stellmann, Jan-Patrick; Heesen, Christoph; Fiehler, Jens; Siemonsen, Susanne

    2017-01-01

    Purpose In patients with multiple sclerosis (MS), Double Inversion Recovery (DIR) magnetic resonance imaging (MRI) can be used to identify cortical lesions (CL). We sought to evaluate the reliability of CL detection on DIR longitudinally at multiple subsequent time-points applying the MAGNIMs scoring criteria for CLs. Methods 26 MS patients received a 3T-MRI (Siemens, Skyra) with DIR at 12 time-points (TP) within a 16 months period. Scans were assessed in random order by two different raters. Both raters separately marked all CLs on each scan and total lesion numbers were obtained for each scan-TP and patient. After a retrospective re-evaluation, the number of consensus CLs (conL) was defined as the total number of CLs, which both raters finally agreed on. CLs volumes, relative signal intensities and CLs localizations were determined. Both ratings (conL vs. non-consensus scoring) were compared for further analysis. Results A total number of n = 334 CLs were identified by both raters in 26 MS patients with a first agreement of both raters on 160 out of 334 of the CLs found (κ = 0.48). After the retrospective re-evaluation, consensus agreement increased to 233 out of 334 CL (κ = 0.69). 93.8% of conL were visible in at least 2 consecutive TP. 74.7% of the conL were visible in all 12 consecutive TP. ConL had greater mean lesion volumes and higher mean signal intensities compared to lesions that were only detected by one of the raters (p<0.05). A higher number of CLs in the frontal, parietal, temporal and occipital lobe were identified by both raters than the number of those only identified by one of the raters (p<0.05). Conclusions After a first assessment, slightly less than a half of the CL were considered as reliably detectable on longitudinal DIR images. A retrospective re-evaluation notably increased the consensus agreement. However, this finding is narrowed, considering the fact that retrospective evaluation steps might not be practicable in clinical routine

  7. Reliability of cortical lesion detection on double inversion recovery MRI applying the MAGNIMS-Criteria in multiple sclerosis patients within a 16-months period.

    PubMed

    Faizy, Tobias Djamsched; Thaler, Christian; Ceyrowski, Tim; Broocks, Gabriel; Treffler, Natascha; Sedlacik, Jan; Stürner, Klarissa; Stellmann, Jan-Patrick; Heesen, Christoph; Fiehler, Jens; Siemonsen, Susanne

    2017-01-01

    In patients with multiple sclerosis (MS), Double Inversion Recovery (DIR) magnetic resonance imaging (MRI) can be used to identify cortical lesions (CL). We sought to evaluate the reliability of CL detection on DIR longitudinally at multiple subsequent time-points applying the MAGNIMs scoring criteria for CLs. 26 MS patients received a 3T-MRI (Siemens, Skyra) with DIR at 12 time-points (TP) within a 16 months period. Scans were assessed in random order by two different raters. Both raters separately marked all CLs on each scan and total lesion numbers were obtained for each scan-TP and patient. After a retrospective re-evaluation, the number of consensus CLs (conL) was defined as the total number of CLs, which both raters finally agreed on. CLs volumes, relative signal intensities and CLs localizations were determined. Both ratings (conL vs. non-consensus scoring) were compared for further analysis. A total number of n = 334 CLs were identified by both raters in 26 MS patients with a first agreement of both raters on 160 out of 334 of the CLs found (κ = 0.48). After the retrospective re-evaluation, consensus agreement increased to 233 out of 334 CL (κ = 0.69). 93.8% of conL were visible in at least 2 consecutive TP. 74.7% of the conL were visible in all 12 consecutive TP. ConL had greater mean lesion volumes and higher mean signal intensities compared to lesions that were only detected by one of the raters (p<0.05). A higher number of CLs in the frontal, parietal, temporal and occipital lobe were identified by both raters than the number of those only identified by one of the raters (p<0.05). After a first assessment, slightly less than a half of the CL were considered as reliably detectable on longitudinal DIR images. A retrospective re-evaluation notably increased the consensus agreement. However, this finding is narrowed, considering the fact that retrospective evaluation steps might not be practicable in clinical routine. Lesions that were not reliably

  8. Fast volumetric imaging of bound and pore water in cortical bone using three-dimensional ultrashort-TE (UTE) and inversion recovery UTE sequences.

    PubMed

    Chen, Jun; Carl, Michael; Ma, Yajun; Shao, Hongda; Lu, Xing; Chen, Bimin; Chang, Eric Y; Wu, Zhihong; Du, Jiang

    2016-10-01

    We report the three-dimensional ultrashort-TE (3D UTE) and adiabatic inversion recovery UTE (IR-UTE) sequences employing a radial trajectory with conical view ordering for bi-component T2 * analysis of bound water (T2 *(BW) ) and pore water (T2 *(PW) ) in cortical bone. An interleaved dual-echo 3D UTE acquisition scheme was developed for fast bi-component analysis of bound and pore water in cortical bone. A 3D IR-UTE acquisition scheme employing multiple spokes per IR was developed for bound water imaging. Two-dimensional UTE (2D UTE) and IR-UTE sequences were employed for comparison. The sequences were applied to bovine bone samples (n = 6) and volunteers (n = 6) using a 3-T scanner. Bi-component fitting of 3D UTE images of bovine samples showed a mean T2 *(BW) of 0.26 ± 0.04 ms and T2 *(PW) of 4.16 ± 0.35 ms, with fractions of 21.5 ± 3.6% and 78.5 ± 3.6%, respectively. The 3D IR-UTE signal showed a single-component decay with a mean T2 *(BW) of 0.29 ± 0.05 ms, suggesting selective imaging of bound water. Similar results were achieved with the 2D UTE and IR-UTE sequences. Bi-component fitting of 3D UTE images of the tibial midshafts of healthy volunteers showed a mean T2 *(BW) of 0.32 ± 0.08 ms and T2 *(PW) of 5.78 ± 1.24 ms, with fractions of 34.2 ± 7.4% and 65.8 ± 7.4%, respectively. Single-component fitting of 3D IR-UTE images showed a mean T2 *(BW) of 0.35 ± 0.09 ms. The 3D UTE and 3D IR-UTE techniques allow fast volumetric mapping of bound and pore water in cortical bone. Copyright © 2016 John Wiley & Sons, Ltd.

  9. A comparison of inner ear imaging features at different time points of sudden sensorineural hearing loss with three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging.

    PubMed

    Zhu, Honglei; Ou, Yongkang; Fu, Jia; Zhang, Ya; Xiong, Hao; Xu, Yaodong

    2015-10-01

    It has been reported that about half of patients with sudden sensorineural hearing loss (SSNHL) show high signals in the affected inner ear on three-dimensional, fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI). These signals may reflect minor hemorrhage or an increased concentration of protein in the inner ear, which has passed through blood vessels with increased permeability. Our objective was to compare the positive ratio of the high signal in affected inner ears at different time points to determine the suitable imaging time point for 3D-FLAIR MRI in SSNHL. 3D-FLAIR MRI images were taken at three times, precontrast and approximately 10 min and 4 h after intravenous injection of a single dose of gadodiamide (Gd) (0.1 mmol/kg), in 46 patients with SNHL. We compared the positive findings of the high signals in the inner ear of patients with SNHL as well as the signal intensity ratio (SIR) between the affected cochleae and unaffected cochleae at three time points. The positive ratios of the high signals in the affected inner ear at the time points of precontrast and 10 min and 4 h after the intravenous Gd injection were 26.1, 32.6, and 41.3%, respectively. The high signal intensity ratios of affected inner ears at the three time points were 1.28, 1.31, and 1.48, respectively. The difference between the positive ratios precontrast and at 10 min after the intravenous Gd injection was statistically significant (P = 0.006); the differences between the positive ratios at 4 h after the intravenous Gd injection and precontrast and between the ratios at 4 h and 10 min after the intravenous Gd injection were not statistically significant. The time effects of the median value of SIR were not significant (P = 0.064). We do not recommend 4 h after intravenous Gd injection as a time point to image the inner ear in SNHL. We believe that imaging precontrast and at 10 min after the intravenous Gd injection are suitable time points.

  10. Magnetic resonance imaging fluid-attenuated inversion recovery sequence signal reduction after endoscopic endonasal transcribiform total resection of olfactory groove meningiomas

    PubMed Central

    Prevedello, Daniel M.; Ditzel Filho, Leo F. S.; Fernandez-Miranda, Juan C.; Solari, Domenico; do Espírito Santo, Marcelo Prudente; Wehr, Allison M.; Carrau, Ricardo L.; Kassam, Amin B.

    2015-01-01

    Background: Olfactory groove meningiomas grow insidiously and compress adjacent cerebral structures. Achieving complete removal without further damage to frontal lobes can be difficult. Microsurgical removal of large lesions is a challenging procedure and usually involves some brain retraction. The endoscopic endonasal approaches (EEAs) for tumors arising from the anterior fossa have been well described; however, their effect on the adjacent brain tissue has not. Herein, the authors utilized the magnetic resonance imaging fluid attenuated inversion recovery (FLAIR) sequence signal as a marker for edema and gliosis on pre- and post-operative images of olfactory groove meningiomas, thus presenting an objective parameter for brain injury after surgical manipulation. Methods: Imaging of 18 olfactory groove meningiomas removed through EEAs was reviewed. Tumor and pre/postoperative FLAIR signal volumes were assessed utilizing the DICOM image viewer OsiriX®. Inclusion criteria were: (1) No previous treatment; (2) EEA gross total removal; (3) no further treatment. Results: There were 14 females and 4 males; the average age was 53.8 years (±8.85 years). Average tumor volume was 24.75 cm3 (±23.26 cm3, range 2.8–75.7 cm3), average preoperative FLAIR volume 31.17 cm3 (±39.38 cm3, range 0–127.5 cm3) and average postoperative change volume, 4.16 cm3 (±6.18 cm3, range 0–22.2 cm3). Average time of postoperative scanning was 6 months (range 0.14–20 months). In all cases (100%) gross total tumor removal was achieved. Nine patients (50%) had no postoperative FLAIR changes. In 2 patients (9%) there was minimal increase of changes postoperatively (2.2 cm3 and 6 cm3 respectively); all others demonstrated image improvement. The most common complication was postoperative cerebrospinal fluid leakage (27.8%); 1 patient (5.5%) died due to systemic complications and pulmonary sepsis. Conclusions: FLAIR signal changes tend to resolve after endonasal tumor resection and do not seem

  11. The Correlation of Stir Zone Texture Development with Base Metal Texture and Tool-Induced Deformation in Friction Stir Processing of Severely Deformed Aluminum

    NASA Astrophysics Data System (ADS)

    Sarkari Khorrami, M.; Kazeminezhad, Mohsen; Miyashita, Y.; Kokabi, A. H.

    2017-01-01

    The texture development during friction stir processing (FSP) of 1050 aluminum severely deformed at the strain magnitude of 2.32 was comprehensively discussed. It was observed that the component bar{B} of the ideal shear texture along with the cube texture was developed in the severely deformed base metal. The effects of base metal texture on the texture development of stir zone, thermo-mechanically affected zone, and heat-affected zone during FSP were examined. Also, the developed texture components in the vicinity of the FSP tool and the stir zone were correlated to the deformation induced by the rotating tool which consisted of pin and shoulder. The observed texture components in the longitudinal section of the stir zone were found coincided with the ideal shear ones, but different from those observed in the severely deformed base metal. It could be responsible for the fact that the material beneath the FSP tool is predominantly deformed and stirred by the shoulder rather than the pin. The independency of texture development in the stir zone from pin-induced deformation was also consistent with the observation associated with the stir zone geometry which was independent of the pin geometry. Microstructural evolutions in the regions located ahead of the FSP tool manifested the incident of static recovery and recrystallization as a result of the stored strain in the severely deformed base metal. These led to the development of almost random texture and the deterioration of base metal texture in this region. This suggested the independency of texture development in the stir zone from the texture of severely deformed base metal.

  12. Friction Stir Welding and NASA

    NASA Technical Reports Server (NTRS)

    Horton, K Renee

    2016-01-01

    Friction stir welding (FSW) is a solid state welding process with potential advantages for aerospace and automotive industries dealing with light alloys. Self-reacting friction stir welding (SR-FSW) is one variation of the FSW process being developed at the National Aeronautics and Space Administration (NASA) for use in the fabrication of propellant tanks and other areas used on the Space Launch System (SLS) NASA's SLS is an advanced, heavy-lift launch vehicle which will provide an entirely new capability for science and human exploration beyond Earth's orbit. The SLS will give the nation a safe, affordable and sustainable means of reaching beyond our current limits and open new doors of discovery from the unique vantage point of space This talk will elaborate on the SR-FSW process and it's usage on the current Space Launch System Program at NASA.

  13. Pulsed ultrasonic stir welding system

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  14. Friction Stir Process Mapping Methodology

    NASA Technical Reports Server (NTRS)

    Kooney, Alex; Bjorkman, Gerry; Russell, Carolyn; Smelser, Jerry (Technical Monitor)

    2002-01-01

    In FSW (friction stir welding), the weld process performance for a given weld joint configuration and tool setup is summarized on a 2-D plot of RPM vs. IPM. A process envelope is drawn within the map to identify the range of acceptable welds. The sweet spot is selected as the nominal weld schedule. The nominal weld schedule is characterized in the expected manufacturing environment. The nominal weld schedule in conjunction with process control ensures a consistent and predictable weld performance.

  15. Flexible Friction Stir Joining Technology

    SciTech Connect

    Feng, Zhili; Lim, Yong Chae; Mahoney, Murray; Sanderson, Samuel; Larsen, Steve; Steel, Russel; Fleck, Dale; Fairchild, Doug P; Wasson, Andrew J; Babb, Jon; Higgins, Paul

    2015-07-23

    Reported herein is the final report on a U.S. Department of Energy (DOE) Advanced Manufacturing Office (AMO) project with industry cost-share that was jointly carried out by Oak Ridge National Laboratory (ORNL), ExxonMobil Upstream Research Company (ExxonMobil), and MegaStir Technologies (MegaStir). The project was aimed to advance the state of the art of friction stir welding (FSW) technology, a highly energy-efficient solid-state joining process, for field deployable, on-site fabrications of large, complex and thick-sectioned structures of high-performance and high-temperature materials. The technology innovations developed herein attempted to address two fundamental shortcomings of FSW: 1) the inability for on-site welding and 2) the inability to weld thick section steels, both of which have impeded widespread use of FSW in manufacturing. Through this work, major advance has been made toward transforming FSW technology from a “specialty” process to a mainstream materials joining technology to realize its pervasive energy, environmental, and economic benefits across industry.

  16. The time window of MRI of murine atherosclerotic plaques after administration of CB2 receptor targeted micelles: inter-scan variability and relation between plaque signal intensity increase and gadolinium content of inversion recovery prepared versus non-prepared fast spin echo.

    PubMed

    te Boekhorst, B C M; Bovens, S M; van de Kolk, C W A; Cramer, M J M; Doevendans, P A F M; ten Hove, M; van der Weerd, L; Poelmann, R; Strijkers, G J; Pasterkamp, G; van Echteld, C J A

    2010-10-01

    Single fast spin echo scans covering limited time frames are mostly used for contrast-enhanced MRI of atherosclerotic plaque biomarkers. Knowledge on inter-scan variability of the normalized enhancement ratio of plaque (NER(plaque)) and relation between NER(plaque) and gadolinium content for inversion-recovery fast spin echo is limited. Study aims were: evaluation of (1) timing of MRI after intravenous injection of cannabinoid-2 receptor (CB2-R) (expressed by human and mouse plaque macrophages) targeted micelles; (2) inter-scan variability of inversion-recovery fast spin echo and fast spin echo; (3) relation between NER(plaque) and gadolinium content for inversion-recovery fast spin echo and fast spin echo. Inversion-recovery fast spin echo/fast spin echo imaging was performed before and every 15 min up to 48 h after injection of CB2-R targeted or control micelles using several groups of mice measured in an interleaved fashion. NER(plaque) (determined on inversion-recovery fast spin echo images) remained high (∼2) until 48 h after injection of CB2-R targeted micelles, whereas NER(plaque) decreased after 36 h in the control group. The inter-scan variability and relation between NER(plaque) and gadolinium (assessed with inductively coupled plasma- mass spectrometry) were compared between inversion-recovery fast spin echo and fast spin echo. Inter-scan variability was higher for inversion-recovery fast spin echo than for fast spin echo. Although gadolinium and NER(plaque) correlated well for both techniques, the NER of plaque was higher for inversion-recovery fast spin echo than for fast spin echo. In mice injected with CB2-R targeted micelles, NER(plaque) can be best evaluated at 36-48 h post-injection. Because NER(plaque) was higher for inversion-recovery fast spin echo than for fast spin echo, but with high inter-scan variability, repeated inversion-recovery fast spin echo imaging and averaging of the obtained NER(plaque) values is recommended.

  17. Stirring effect on kaolinite dissolution rate

    NASA Astrophysics Data System (ADS)

    Metz, Volker; Ganor, Jiwchar

    2001-10-01

    Experiments were carried out measuring kaolinite dissolution rates using stirred and nonstirred flow-through reactors at pHs 2 to 4 and temperatures of 25°C, 50°C, and 70°C. The results show an increase of kaolinite dissolution rate with increasing stirring speed. The stirring effect is reversible, i.e., as the stirring slows down the dissolution rate decreases. The effect of stirring speed on kaolinite dissolution rate is higher at 25°C than at 50°C and 70°C and at pH 4 than at pHs 2 and 3. It is suggested that fine kaolinite particles are formed as a result of stirring-induced spalling or abrasion of kaolinite. These very fine particles have an increased ratio of reactive surface area to specific surface area, which results in enhancement of kaolinite dissolution rate. A balance between production and dissolution of the fine particles explains both the reversibility and the temperature and pH dependence of the stirring effect. Since the stirring effect on kaolinite dissolution rate varies with temperature and pH, measurement of kinetic parameters such as activation energy may be influenced by stirring. Therefore, standard use of nonagitated reaction vessels for kinetic experiments of mineral dissolution and precipitation is recommended, at least for slow reactions that are surface controlled.

  18. Anterior temporal lobe white matter abnormal signal (ATLAS) as an indicator of seizure focus laterality in temporal lobe epilepsy: comparison of double inversion recovery, FLAIR and T2W MR imaging.

    PubMed

    Morimoto, Emiko; Kanagaki, Mitsunori; Okada, Tomohisa; Yamamoto, Akira; Mori, Nobuyuki; Matsumoto, Riki; Ikeda, Akio; Mikuni, Nobuhiro; Kunieda, Takeharu; Paul, Dominik; Miyamoto, Susumu; Takahashi, Ryosuke; Togashi, Kaori

    2013-01-01

    To investigate the diagnostic capability of anterior temporal lobe white matter abnormal signal (ATLAS) for determining seizure focus laterality in temporal lobe epilepsy (TLE) by comparing different MR sequences. This prospective study was approved by the institutional review board and written informed consent was obtained. Three 3D sequences (double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging (T2WI)) and two 2D sequences (FLAIR and T2WI) were acquired at 3 T. Signal changes in the anterior temporal white matter of 21 normal volunteers were evaluated. ATLAS laterality was evaluated in 21 TLE patients. Agreement of independent evaluations by two neuroradiologists was assessed using κ statistics. Differences in concordance between ATLAS laterality and clinically defined seizure focus laterality were analysed using McNemar's test with multiple comparisons. Pre-amygdala high signals (PAHS) were detected in all volunteers only on 3D-DIR. Inter-evaluator agreement was moderate to almost perfect for each sequence. Correct diagnosis of seizure laterality was significantly more frequent on 3D-DIR than on any other sequences (P ≤ 0.031 for each evaluator). The most sensitive sequence for detecting ATLAS laterality was 3D-DIR. ATLAS laterality on 3D-DIR can be a good indicator for determining seizure focus localization in TLE.

  19. Pulsed ultrasonic stir welding method

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  20. [Uterine inversion].

    PubMed

    Neves, J; Cardoso, E; Araújo, C; Santo, S; Gonçalves, P; Melo, A; Rodrigues, R; Coelho, A Pereira

    2006-01-01

    The uterine inversion is a rare but serious pathology of the delivery. We describe two cases of uterine inversion of secondary and quaternary degree; the first had a delay diagnosis and the second having a return after the manual replacement, finishing both on surgical resolution. The authors describe the causal factors, the diagnosis and the therapeutic of uterine inversion.

  1. Modelling and simulation of a copper slag cleaning process improved by electromagnetic stirring

    NASA Astrophysics Data System (ADS)

    Yang, H.; Wolters, J.; Pischke, P.; Soltner, H.; Eckert, S.; Natour, G.; Fröhlich, J.

    2017-07-01

    Electromagnetic stirring in a copper slag cleaning process aims at improving the recovery efficiency of the finely dispersed metallic materials from the waste. In the present study the multiphase problems involved in the slag cleaning process are numerically investigated. An Euler-Lagrange approach with advanced collision and coalescence modelling is employed. The corresponding methodologies are briefly introduced and discussed. Based on the implemented sub-models, the copper recovery is numerically investigated for operating parameters corresponding to industrial pilot plants.

  2. Wiping Metal Transfer in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Much evidence suggests that as the friction stir pin-tool moves along a weld seam the displacement of metal takes place by a wiping action at the surface of a plug of metal that rotates with the tool. The wiping model is explained and some consequences for the friction stir welding process are drawn.

  3. Gimbaled-shoulder friction stir welding tool

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Lawless, Kirby G. (Inventor)

    2010-01-01

    A gimbaled-shoulder friction stir welding tool includes a pin and first and second annular shoulders coupled to the pin. At least one of the annular shoulders is coupled to the pin for gimbaled motion with respect thereto as the tool is rotated by a friction stir welding apparatus.

  4. Stirring properties of vortex rings

    NASA Astrophysics Data System (ADS)

    Auerbach, David

    1991-05-01

    Ring vortex evolution, from the initial roll-up phase through to the final turbulent phase, was experimentally studied to see the dependence of its stirring properties on both the initial (accelerating, constant, decelerating, slow, fast) piston motion as well as on the boundary (tube/hole geometry) conditions. Stirring between fluid initially upstream and that initially downstream of the nozzle plane is done more by convective entrainment at the beginning (roll-up and contraction phases), by diffusive entrainment during the laminar and wavy phases, and by mixed entrainment and ejection during the transition to turbulence and the turbulent phase itself. During vortex roll-up, it was found that tubes eject shorter streaklines than do holes, and that there is less Re dependence for this for tubes than for holes. During the contraction phase, entrainment ends, save for minimal entrainment due to axial inflow into the ring from along the cores of Goertler-type vortices. Generally, the rate of fluid ejected is largest during the transition from the wavy to the turbulent state. As far as the stability of the vortices is concerned, rings generated at holes are less stable than those generated at tubes. During the final turbulent phase, rings not only entrain fluid but eject it periodically into the wake: Between two and four hairpin vortices are generated and laid off in the wake during each ejection. The frequency at which such ejections takes place scales as a Strouhal number that takes on values of between 2 and 4.

  5. In vitro recovery of triamcinolone acetonide in microdialysis.

    PubMed

    Rojas, C; Nagaraja, N V; Derendorf, H

    2000-09-01

    The purpose of this study was to assess the factors affecting the calibration of the microdialysis probe for the in vitro recovery of triamcinolone acetonide (TA). Recoveries of TA were determined in microdialysis, retrodialysis, and no-net flux methods. Experiments were performed at room temperature or 37 degrees C while the reservoir medium was either stirred or unstirred. The effect of the viscosity of the medium on the recovery was studied using methylcellulose gel spiked with TA. Recovery was also calculated by the no-net-flux method in Ringer's solution and in plasma. Stirring the medium increased the recovery of TA by 30%. The recovery was higher at 37 degrees C under stirred or unstirred conditions and was same in either direction of dialysis. Increasing viscosity of the reservoir medium decreased the recovery (55% in Ringer's solution to 14% in 20% methylcellulose gel). Recovery from spiked plasma under stirred conditions was only 15% and this shift which was also seen in no-net-flux method was accounted for by the protein binding. Binding of TA, determined by ultrafiltration, was 20% in 5% gel and 81% in plasma. The recovery determined by the no-net-flux method was similar to the retrodialysis result. Stirring, temperature, viscosity and protein binding in the reservoir medium affected the in vitro recovery of TA.

  6. [Uterine inversion].

    PubMed

    Dirken, J J; Vlaanderen, W

    1994-01-01

    Inversion of the uterus is a rare complication of childbirth. A primigravida aged 21 and a multigravida aged 32, hospitalized as emergency cases because of inversion of the uterus with major blood loss, were treated with infusion of liquids (to combat shock), repositioning of the uterus under anaesthesia and prevention of reinversion by uterine tonics. Inversion of the uterus should be part of the differential diagnosis in every case of fluxus post partum.

  7. Macrostructure of Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Aloor, S.; Nowak, B.; Vargas, R.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    This paper will discuss two of the well know large scale features of friction stir welds: the "onion rings" seen in transverse sections, and the striations on the surface of the work piece. It will be shown that the surface features (sometimes called "tool marks") are the result of irregularities on the rotating shoulder of the pin tool and disappear when the shoulder is polished. The "onion ring" structure seen in transverse cross sections is formed by parts of the "carousel", the zone of material adjacent to and rotating with the pin tool, that are shed off in each rotation. The relation between the carousel and the "ring vortex", a rotational flow extending both in and out of the carousel and resembling a smoke-ring with the hole centered on the pin tool, will be discussed.

  8. Friction Stir Welding and Processing

    SciTech Connect

    Hovanski, Yuri; Carsley, John; Clarke, Kester D.; Krajewski, Paul E.

    2015-05-01

    With nearly twenty years of international research and collaboration in friction stir welding (FSW) and processing industrial applications have spread into nearly every feasible market. Currently applications exist in aerospace, railway, automotive, personal computers, technology, marine, cutlery, construction, as well as several other markets. Implementation of FSW has demonstrated diverse opportunities ranging from enabling new materials to reducing the production costs of current welding technologies by enabling condensed packaging solutions for traditional fabrication and assembly. TMS has sponsored focused instruction and communication in this technology area for more than fifteen years, with leadership from the Shaping and Forming Committee, which organizes a biannual symposium each odd year at the annual meeting. A focused publication produced from each of these symposia now comprises eight volumes detailing the primary research and development activities in this area over the last two decades. The articles assembled herein focus on both recent developments and technology reviews of several key markets from international experts in this area.

  9. Partitioning of main and side-chain units between different phases: a solid-state 13C NMR inversion-recovery cross-polarization study on a homogeneous, metallocene-based, ethylene-1-octene copolymer.

    PubMed

    Litvinov, Victor M; Mathot, Vincent B F

    2002-01-01

    13C NMR inversion-recovery cross-polarization experiments are used to study the phase structure and partitioning of main and side-chain groups in a homogeneous, metallocene-based, ethylene-1-octene copolymer. The results provide strong evidence for a three-phase model, i.e. a rigid, (imperfect) crystalline phase, which is mainly composed of long sequences of methylene carbon atoms of the main chain, a semi-rigid, amorphous interphase (also denoted as 'rigid amorphous'), which is enriched by chain segments bearing methylene and methine carbon atoms of the main chain, and a soft fraction of the amorphous phase (also denoted as 'mobile amorphous'), which is largely composed of side chains and short methylene sequences of the main chain.

  10. Myocardial T1 Mapping at 3.0T Using an Inversion Recovery Spoiled Gradient Echo Readout and Bloch Equation Simulation with Slice Profile Correction (BLESSPC) T1 Estimation Algorithm

    PubMed Central

    Shao, Jiaxin; Rapacchi, Stanislas; Nguyen, Kim-Lien; Hu, Peng

    2015-01-01

    Purpose To develop an accurate and precise myocardial T1 mapping technique using an inversion recovery spoiled gradient echo readout at 3.0T. Materials and Methods The modified Look-Locker inversion-recovery (MOLLI) sequence was modified to use fast low angle shot (FLASH) readout, incorporating a BLESSPC (Bloch Equation Simulation with Slice Profile Correction) T1 estimation algorithm, for accurate myocardial T1 mapping. The FLASH-MOLLI with BLESSPC fitting was compared to different approaches and sequences with regards to T1 estimation accuracy, precision and image artifact based on simulation, phantom studies, and in vivo studies of 10 healthy volunteers and 3 patients at 3.0T. Results The FLASH-MOLLI with BLESSPC fitting yields accurate T1 estimation (average error = −5.4±15.1 ms, percentage error = −0.5%±1.2%) for T1 from 236–1852 ms and heart rate from 40–100 bpm in phantom studies. The FLASH-MOLLI sequence prevented off-resonance artifacts in all 10 healthy volunteers at 3.0T. In vivo, there was no significant difference between FLASH-MOLLI-derived myocardial T1 values and “ShMOLLI+IE” derived values (1458.9±20.9 ms vs. 1464.1±6.8 ms, p=0.50); However, the average precision by FLASH-MOLLI was significantly better than that generated by “ShMOLLI+IE” (1.84±0.36% variance vs. 3.57±0.94%, p<0.001). Conclusion The FLASH-MOLLI with BLESSPC fitting yields accurate and precise T1 estimation, and eliminates banding artifacts associated with bSSFP at 3.0T. PMID:26214152

  11. What Adolescents Stir up in Me.

    ERIC Educational Resources Information Center

    Dupont, Philippe J.

    2001-01-01

    Fritz Redl challenged professionals to examine situations in which adolescents stir up negative feelings in them. The author also applies Redl's concepts to his own work in administering a school for troubled students. (Author)

  12. Material Flow in Friction Stir Welds

    NASA Astrophysics Data System (ADS)

    Fonda, Richard; Reynolds, Anthony; Feng, C. R.; Knipling, Keith; Rowenhorst, David

    2013-01-01

    Friction stir welding generates periodic features within the weld. These "onion ring" features are associated with variations in both texture and the orientation of that texture along the length of the weld. Analysis of an AA2195 friction stir weld reveals the presence of periodic oscillations between the dominant B and overline{{B}} components of the ideal shear texture, suggesting a periodic reversal in the predominant shear orientation during welding that is inconsistent with current understandings of the friction stir welding process. Microstructural features present in the weld and machine force variations during welding indicate that these textures may arise from the oscillation of an off-centered tool. Such a tool oscillation can generate a periodic extrusion of material around the tool, giving rise to the observed flow features, machine force variations, and reversals of the local shear texture orientations. A new model of material flow during friction stir welding is proposed to explain the observed features.

  13. Gimballed Shoulders for Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Carter, Robert; Lawless, Kirby

    2008-01-01

    In a proposed improvement of tooling for friction stir welding, gimballed shoulders would supplant shoulders that, heretofore, have been fixedly aligned with pins. The proposal is especially relevant to self-reacting friction stir welding. Some definitions of terms, recapitulated from related prior NASA Tech Briefs articles, are prerequisite to a meaningful description of the proposed improvement. In friction stir welding, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a pin that rotates with the shoulder and protrudes from the shoulder into the depth of the workpiece. In conventional friction stir welding, the main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional friction stir welding is augmented with an auto-adjustable pin-tool (APT) capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or forcecontrol system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding as practiced heretofore, there are two shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. Both shoulders rotate with the pin and remain aligned coaxially with the pin. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft into the friction-stir-welding machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. This concludes the prerequisite definitions of terms.

  14. Numerical Simulation of Tension Properties for Al-Cu Alloy Friction Stir-Welded Joints with GTN Damage Model

    NASA Astrophysics Data System (ADS)

    Sun, Guo-Qin; Sun, Feng-Yang; Cao, Fang-Li; Chen, Shu-Jun; Barkey, Mark E.

    2015-11-01

    The numerical simulation of tensile fracture behavior on Al-Cu alloy friction stir-welded joint was performed with the Gurson-Tvergaard-Needleman (GTN) damage model. The parameters of the GTN model were studied in each region of the friction stir-welded joint by means of inverse identification. Based on the obtained parameters, the finite element model of the welded joint was built to predict the fracture behavior and tension properties. Good agreement can be found between the numerical and experimental results in the location of the tensile fracture and the mechanical properties.

  15. Stir bar sorptive extraction of diclofenac from liquid formulations: a proof of concept study.

    PubMed

    Kole, Prashant Laxman; Millership, Jeff; McElnay, James C

    2011-03-25

    A new stir bar sorptive extraction (SBSE) technique coupled with HPLC-UV method for quantification of diclofenac in pharmaceutical formulations has been developed and validated as a proof of concept study. Commercially available polydimethylsiloxane stir bars (Twister™) were used for method development and SBSE extraction (pH, phase ratio, stirring speed, temperature, ionic strength and time) and liquid desorption (solvents, desorption method, stirring time etc) procedures were optimised. The method was validated as per ICH guidelines and was successfully applied for the estimation of diclofenac from three liquid formulations viz. Voltarol(®) Optha single dose eye drops, Voltarol(®) Ophtha multidose eye drops and Voltarol(®) ampoules. The developed method was found to be linear (r=0.9999) over 100-2000ng/ml concentration range with acceptable accuracy and precision (tested over three QC concentrations). The SBSE extraction recovery of the diclofenac was found to be 70% and the LOD and LOQ of the validated method were found to be 16.06 and 48.68ng/ml, respectively. Furthermore, a forced degradation study of a diclofenac formulation leading to the formation of structurally similar cyclic impurity (indolinone) was carried out. The developed extraction method showed comparable results to that of the reference method, i.e. method was capable of selectively extracting the indolinone and diclofenac from the liquid matrix. Data on inter and intra stir bar accuracy and precision further confirmed robustness of the method, supporting the multiple re-use of the stir bars. Copyright © 2010 Elsevier B.V. All rights reserved.

  16. Molecularly imprinted polymer monolith containing magnetic nanoparticles for the stir-bar sorptive extraction of triazines from environmental soil samples.

    PubMed

    Díaz-Álvarez, Myriam; Turiel, Esther; Martín-Esteban, Antonio

    2016-10-21

    In this work, novel molecularly imprinted stir-bars based upon the entrapment of modified magnetic nanoparticles within an imprinted polymer monolith is developed for stir-bar sorptive extraction (SBSE). Firstly, magnetic nanoparticles were surface modified with oleic acid followed by encapsulation inside a silica network. Then, vinyl-groups were grafted onto the particles surface for the subsequent copolymerization with the imprinting polymerization mixture using a glass vial insert as a mold. As a result, the obtained imprinted monolith presented magnetic properties allowing its use as magnetic stir-bar. Variables affecting both polymer morphology (i.e., amount of magnetic nanoparticles, polymerization time) and binding-elution conditions of target analytes (i.e., solvents, time) was carefully optimized. Optimum imprinted stir-bars were evaluated for the SBSE of triazines in soil sample extracts. Recoveries, at 16ngg(-1) concentration level, ranged from 2.4 to 8.7% with relative standard deviations lower than 15% (n=3). Although low recoveries were obtained, the high selectivity provided by the new molecularly imprinted stir-bars allowed reaching detection limits below 7.5ngg(-1) by liquid chromatography coupled to UV detection.

  17. Friction Stir Welding of Steel Alloys

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The friction stir welding process has been developed primarily for the welding of aluminum alloys. Other higher melting allows such, as steels are much more difficult to join. Special attention must be given to pin tool material selection and welding techniques. This paper addresses the joining of steels and other high melting point materials using the friction stir welding process. Pin tool material and welding parameters will be presented. Mechanical properties of weldments will also be presented. Significance: There are many applications for the friction stir welding process other than low melting aluminum alloys. The FSW process can be expanded for use with high melting alloys in the pressure vessel, railroad and ship building industries.

  18. Friction Stir Welding of Steel Alloys

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The friction stir welding process has been developed primarily for the welding of aluminum alloys. Other higher melting allows such, as steels are much more difficult to join. Special attention must be given to pin tool material selection and welding techniques. This paper addresses the joining of steels and other high melting point materials using the friction stir welding process. Pin tool material and welding parameters will be presented. Mechanical properties of weldments will also be presented. Significance: There are many applications for the friction stir welding process other than low melting aluminum alloys. The FSW process can be expanded for use with high melting alloys in the pressure vessel, railroad and ship building industries.

  19. An analytical model which determines the apparent T1 for Modified Look-Locker Inversion Recovery - Analysis of the longitudinal relaxation under the influence of discontinuous balanced (classical MOLLI) and spoiled gradient echo readouts.

    PubMed

    Kampf, Thomas; Reiter, Theresa; Bauer, Wolfgang Rudolf

    2017-08-09

    Quantitative nuclear magnetic resonance imaging (MRI) shifts more and more into the focus of clinical research. Especially determination of relaxation times without/and with contrast agents becomes the foundation of tissue characterization, e.g. in cardiac MRI for myocardial fibrosis. Techniques which assess longitudinal relaxation times rely on repetitive application of readout modules, which are interrupted by free relaxation periods, e.g. the Modified Look-Locker Inversion Recovery = MOLLI sequence. These discontinuous sequences reveal an apparent relaxation time, and, by techniques extrapolated from continuous readout sequences, a putative real T1 is determined. What is missing is a rigorous analysis of the dependence of the apparent relaxation time on its real partner, readout sequence parameters and biological parameters as heart rate. This is provided in this paper for the discontinuous balanced steady state free precession (bSSFP) and spoiled gradient echo readouts. It turns out that the apparent longitudinal relaxation rate is the time average of the relaxation rates during the readout module, and free relaxation period. Knowing the heart rate our results vice versa allow to determine the real T1 from its measured apparent partner. Copyright © 2017. Published by Elsevier GmbH.

  20. Study of stirred layers on 316L steel created by friction stir processing

    NASA Astrophysics Data System (ADS)

    Langlade, C.; Roman, A.; Schlegel, D.; Gete, E.; Folea, M.

    2014-08-01

    Nanostructured materials are known to exhibit attractive properties, especially in the mechanical field where high hardness is of great interest. The friction stir process (FSP) is a recent surface engineering technique derived from the friction stir welding method (FSW). In this study, the FSP of an 316L austenitic stainless steel has been evaluated. The treated layers have been characterized in terms of hardness and microstructure and these results have been related to the FSP operational parameters. The process has been analysed using a Response Surface Method (RSM) to enable the stirred layer thickness prediction.

  1. Stir bar sorptive extraction-thermal desorption-capillary GC-MS applied to biological fluids.

    PubMed

    Tienpont, B; David, F; Desmet, K; Sandra, P

    2002-05-01

    A new sample preparation method, stir bar sorptive extraction (SBSE), has been evaluated for the enrichment of organic solutes from biological fluids such as urine and blood. In SBSE, a stir bar coated with a polydimethylsiloxane layer is stirred for a given time in the sample. After sampling the stir bar is placed in a thermal desorption unit coupled on-line to capillary gas chromatography-mass spectrometry (SBSE-TD-CGC-MS). The principle and operation of SBSE are presented. Total profiling and target compound analysis have been selected as applications to illustrate the performance of SBSE-TD-CGC-MS (MSD). It is demonstrated that a variety analytes ranging from biological markers (phenols, hormones, fatty acids) to artificial contaminants (recreational drugs, plasticizers) can be enriched with high sensitivity. For polar solutes, in-situ derivatization can enhance both recovery into the polydimethylsiloxane (PDMS) layer and chromatographic analysis. Two types of derivatization have been applied, derivatization with ethyl chloroformate and with acetic acid anhydride. Linearity, detectability, and repeatability are illustrated by the determination of 1-hydroxypyrene in a urine sample from a smoker.

  2. Control of Protein Crystal Nucleation and Growth Using Stirring Solution

    NASA Astrophysics Data System (ADS)

    Niino, Ai; Adachi, Hiroaki; Takano, Kazufumi; Matsumura, Hiroyoshi; Kinoshita, Takayoshi; Warizaya, Masaichi; Inoue, Tsuyoshi; Mori, Yusuke; Sasaki, Takatomo

    2004-11-01

    We have previously developed a protein crystallization technique using a stirring protein solution and revealed that (i) continuous stirring prevents excess spontaneous nucleation and accelerates the growth of protein crystals and (ii) prestirring (solution stirring in advance) promotes the crystal nucleation of hen egg-white lysozyme. In bovine adenosine deaminase (ADA) crystallization, continuous stirring improves the crystal quality but elongates the nucleation time. In this paper, in order to control both the crystal nucleation and growth of ADA using a Micro-Stirring technique, we carried out five different stirring patterns such as (i) no stirring, (ii) continuous stirring, (iii) prestirring, (iv) poststirring (stirring late in the growth period) and (v) restirring (combined pre- and poststirring). The results showed that high-quality well-shaped crystals were obtained under the continuous stirring and restirring conditions and the nucleation time under the prestirring and restirring conditions was shorter than that under the continuous stirring and poststirring conditions. Consequently, high-quality crystals were promptly obtained under the restirring condition. These results suggest that we are able to control both the nucleation and growth of protein crystals with the stirring techniques.

  3. Friction Stir & Ultrasonic Solid State Joining Magnesium

    SciTech Connect

    Grant, Glenn J.; Hovanski, Yuri; Santella, M. L.

    2009-12-30

    Solid state joining between automotive sheet steel and magnesium alloys was investigated. Both friction stir welding and ultrasonic welding were utilized to study the potential for creating structural bonds between these dissimilar materials. A detailed investigation into the joint characteristics was undertaken including an evaluation of joint strength, microstructure, chemical structures, and alloy formation.

  4. Stirring the Ashes of Public Discourse.

    ERIC Educational Resources Information Center

    Marinara, Martha

    Sylvia Plath's confessional poem, "Lady Lazarus" can be used to illustrate a connection between autobiography and social critique. "You poke and stir" among the institutions that form social relations--the educational system, the court system, the economic system--to find individuals whose lives, whose joys and pains, and…

  5. School-Meals Makeover Stirs the Pot

    ERIC Educational Resources Information Center

    Shah, Nirvi

    2011-01-01

    Proposed new federal rules governing the meals served to school children across the country each weekday are causing a stir among food industry groups, cafeteria managers, parents, and students. The skirmish is over the U.S. Department of Agriculture's efforts, prompted by the recent passage of the Healthy, Hunger-Free Kids Act, to rewrite the…

  6. School-Meals Makeover Stirs the Pot

    ERIC Educational Resources Information Center

    Shah, Nirvi

    2011-01-01

    Proposed new federal rules governing the meals served to school children across the country each weekday are causing a stir among food industry groups, cafeteria managers, parents, and students. The skirmish is over the U.S. Department of Agriculture's efforts, prompted by the recent passage of the Healthy, Hunger-Free Kids Act, to rewrite the…

  7. Indirect inversions

    NASA Astrophysics Data System (ADS)

    Sergienko, Olga

    2013-04-01

    Since Doug MacAyeal's pioneering studies of the ice-stream basal traction optimizations by control methods, inversions for unknown parameters (e.g., basal traction, accumulation patterns, etc) have become a hallmark of the present-day ice-sheet modeling. The common feature of such inversion exercises is a direct relationship between optimized parameters and observations used in the optimization procedure. For instance, in the standard optimization for basal traction by the control method, ice-stream surface velocities constitute the control data. The optimized basal traction parameters explicitly appear in the momentum equations for the ice-stream velocities (compared to the control data). The inversion for basal traction is carried out by minimization of the cost (or objective, misfit) function that includes the momentum equations facilitated by the Lagrange multipliers. Here, we build upon this idea, and demonstrate how to optimize for parameters indirectly related to observed data using a suite of nested constraints (like Russian dolls) with additional sets of Lagrange multipliers in the cost function. This method opens the opportunity to use data from a variety of sources and types (e.g., velocities, radar layers, surface elevation changes, etc.) in the same optimization process.

  8. Effects of Solution Stirring on Protein Crystal Growth

    NASA Astrophysics Data System (ADS)

    Yaoi, Mari; Aadachi, Hiroaki; Takano, Kazufumi; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Mori, Yusuke; Sasaki, Takatomo

    2004-05-01

    We report the influence of solution stirring on the growth of hen egg white lysozyme crystals. Solution stirring rate was controlled by varying the rotation speed of a rotary shaker. A range of precipitation agent (sodium chloride) concentrations was also investigated. The time required for crystal nucleation to occur was observed to be much greater in stirred samples than in unstirred samples. Solution stirring resulted in a reduced number of crystals (at sodium chloride concentrations from 6 to 9%). These crystals were larger and of a higher quality. However, the time required for nucleation to occur was reduced by gentle stirring (25 and 50 rpm) in a 12.5% sodium chloride concentration solution, suggesting that stirring can stimulate nucleation. These results indicate that the optimization of solution stirring rates is a useful technique for controlling protein crystal growth.

  9. Thermal Stir Welding: A New Solid State Welding Process

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey

    2003-01-01

    Thermal stir welding is a new welding process developed at NASA's Marshall Space Flight Center in Huntsville, AL. Thermal stir welding is similar to friction stir welding in that it joins similar or dissimilar materials without melting the parent material. However, unlike friction stir welding, the heating, stirring and forging elements of the process are all independent of each other and are separately controlled. Furthermore, the heating element of the process can be either a solid-state process (such as a thermal blanket, induction type process, etc), or, a fusion process (YG laser, plasma torch, etc.) The separation of the heating, stirring, forging elements of the process allows more degrees of freedom for greater process control. This paper introduces the mechanics of the thermal stir welding process. In addition, weld mechanical property data is presented for selected alloys as well as metallurgical analysis.

  10. Thermal Stir Welding: A New Solid State Welding Process

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Thermal stir welding is a new welding process developed at NASA's Marshall Space Flight Center in Huntsville, AL. Thermal stir welding is similar to friction stir welding in that it joins similar or dissimilar materials without melting the parent material. However, unlike friction stir welding, the heating, stirring and forging elements of the process are all independent of each other and are separately controlled. Furthermore, the heating element of the process can be either a solid-state process (such as a thermal blanket, induction type process, etc), or, a fusion process (YG laser, plasma torch, etc.) The separation of the heating, stirring, forging elements of the process allows more degrees of freedom for greater process control. This paper introduces the mechanics of the thermal stir welding process. In addition, weld mechanical property data is presented for selected alloys as well as metallurgical analysis.

  11. Thermal Stir Welding: A New Solid State Welding Process

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey

    2003-01-01

    Thermal stir welding is a new welding process developed at NASA's Marshall Space Flight Center in Huntsville, AL. Thermal stir welding is similar to friction stir welding in that it joins similar or dissimilar materials without melting the parent material. However, unlike friction stir welding, the heating, stirring and forging elements of the process are all independent of each other and are separately controlled. Furthermore, the heating element of the process can be either a solid-state process (such as a thermal blanket, induction type process, etc), or, a fusion process (YG laser, plasma torch, etc.) The separation of the heating, stirring, forging elements of the process allows more degrees of freedom for greater process control. This paper introduces the mechanics of the thermal stir welding process. In addition, weld mechanical property data is presented for selected alloys as well as metallurgical analysis.

  12. Thermal Stir Welding: A New Solid State Welding Process

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Thermal stir welding is a new welding process developed at NASA's Marshall Space Flight Center in Huntsville, AL. Thermal stir welding is similar to friction stir welding in that it joins similar or dissimilar materials without melting the parent material. However, unlike friction stir welding, the heating, stirring and forging elements of the process are all independent of each other and are separately controlled. Furthermore, the heating element of the process can be either a solid-state process (such as a thermal blanket, induction type process, etc), or, a fusion process (YG laser, plasma torch, etc.) The separation of the heating, stirring, forging elements of the process allows more degrees of freedom for greater process control. This paper introduces the mechanics of the thermal stir welding process. In addition, weld mechanical property data is presented for selected alloys as well as metallurgical analysis.

  13. Spectral presaturation inversion recovery MR imaging sequence after gadolinium injection to differentiate fibrotic scar tissue and neoplastic strands in the mesorectal fat in patients undergoing restaging of rectal carcinoma after neoadjuvant chemo- and radiation therapy.

    PubMed

    Quaia, Emilio; Ulcigrai, Veronica; Coss, Matteo; De Paoli, Luca; Ukmar, Maja; Zanconati, Fabrizio; De Pellegrin, Alessandro; De Manzini, Nicolò; Cova, Maria Assunta

    2011-11-01

    To retrospectively assess the value of spectral presaturation by inversion-recovery (SPIR) magnetic resonance (MR) imaging sequence after gadolinium injection to differentiate fibrotic scar tissue and tumoral infiltration within the mesorectal fat in patients with rectal carcinoma undergoing MR restaging after neoadjuvant chemo- and radiation therapy (CRT). Forty-three consecutive patients (mean age, 65.8 years; range, 46-85 years; male:female, 29:14) with locally advanced rectal carcinoma underwent CRT followed by surgery. MR imaging was performed before and after completion of CRT by using T2-weighted turbo spin-echo and T1-weighted SPIR sequences before and after gadolinium injection, and MR images were assessed by two radiologists in consensus. Logistic regression was conducted to test the significance of the MR image findings with histology. After CRT the disease was either limited to the rectal wall (n = 18 patients) or presented perirectal infiltration (n = 25) on histology. In 21 patients, mesorectal enhancing strands were observed. Reticular-shaped enhancing strands reaching the mesorectal fascia presented the highest correlation with tumor infiltration of the mesorectal fat (OR 130.33, 95% CI: 4.1-4220.29; logistic regression), whereas linear-shaped enhancing strands either reaching or not reaching the mesorectal fascia (OR 0.25 or 0.1, 95% CI: 0.024-2.6 or 0.01-1.07) revealed the lowest correlation. Reticular-shaped enhancing strands on SPIR MR imaging after gadolinium injection are associated with tumor infiltration of the mesorectal fat. Copyright © 2011 AUR. Published by Elsevier Inc. All rights reserved.

  14. Added value of high-b-value (b = 3000 s/mm2) diffusion-weighted imaging at 3 T in relation to fluid-attenuated inversion recovery images for the evaluation of cortical lesions in inflammatory brain diseases.

    PubMed

    Iwashita, Koya; Hirai, Toshinori; Kitajima, Mika; Shigematsu, Yoshinori; Uetani, Hiroyuki; Iryo, Yasuhiko; Azuma, Minako; Hayashida, Eri; Ando, Yukio; Murakami, Ryuji; Yamashita, Yasuyuki

    2013-01-01

    The purpose of this study was to determine how the gray-to-white matter contrast in healthy subjects changes on high-b-value diffusion-weighted imaging (DWI) acquired at 3 T and evaluate whether high-b-value DWI at 3 T is useful for the detection of cortical lesions in inflammatory brain diseases. Ten healthy volunteers underwent DWI at b = 1000, 2000, 3000, 4000, and 5000 s/mm(2) on a 3-T MRI unit. On DW images, 1 radiologist performed region-of-interest measurements of the signal intensity of 8 gray matter structures. The gray-to-white matter contrast ratio (GWCR) was calculated. Ten patients with inflammatory cortical lesions were also included. All patients underwent conventional MRI and DWI at b = 1000 and 3000 s/mm(2). Using a 4-point grading system, 2 radiologists independently assessed the presence of additional information on DW images compared with fluid-attenuated inversion recovery images. Interobserver agreement was assessed by κ statistics. In the healthy subjects, the b value increased as the GWCR decreased in all evaluated gray matter structures. On DW images acquired at b = 3000 s/mm(2), mean GWCR was less than 1.0 in 7 of 8 structures. For both reviewers, DWI at b = 3000 s/mm(2) yielded significantly more additional information than did DWI at b = 1000 s/mm(2) (P < 0.05). Interobserver agreement for DWI at b = 1000 s/mm(2) and b = 3000 s/mm(2) was fair (κ = 0.35) and excellent (κ = 1.0), respectively. At 3-T DWI, the gray-to-white matter contrast in most gray matter structures reverses at b = 3000 s/mm. In the evaluation of cortical lesions in patients with inflammatory brain diseases, 3-T DWI at b = 3000 s/mm was more useful than b = 1000 s/mm(2).

  15. A prospective comparison study of fast T1 weighted fluid attenuation inversion recovery and T1 weighted turbo spin echo sequence at 3 T in degenerative disease of the cervical spine

    PubMed Central

    Bydder, G M

    2014-01-01

    Objective: This study compared T1 fluid attenuation inversion recovery (FLAIR) and T1 turbo spin echo (TSE) sequences for evaluation of cervical spine degenerative disease at 3 T. Methods: 72 patients (44 males and 28 females; mean age of 39 years; age range, 27–75 years) with suspected cervical spine degenerative disease were prospectively evaluated. Sagittal images of the spine were obtained using T1 FLAIR and T1 TSE sequences. Two experienced neuroradiologists compared the sequences qualitatively and quantitatively. Results: On qualitative evaluation, cerebrospinal fluid (CSF) nulling and contrast at cord–CSF, disc–CSF and disc–cord interfaces were significantly higher on fast T1 FLAIR images than on T1 TSE images (p < 0.001). No significant difference was seen between the sequences in evaluation of neural foramina and bone–disc interface. On quantitative evaluation, the signal-to-noise ratios of cord and CSF on fast T1 FLAIR images were significantly higher than those on T1 TSE images (p < 0.05). Contrast-to-noise ratios (CNRs) of cord to CSF on T1 FLAIR images were significantly higher than those of T1 TSE images (p < 0.05). CNRs of bone to disc for T1 weighted TSE images were significantly higher than those of T1 FLAIR images (p < 0.05). Conclusion: At 3 T, T1 FLAIR imaging is superior to T1 TSE for evaluating cervical spine degenerative disease, owing to higher cord–CSF, disc–cord and disc–CSF contrast. However, intrinsic cord contrast is low on T1 FLAIR images. Advances in knowledge: T1 FLAIR is more promising and sensitive than T1 TSE for evaluation of degenerative spondyloarthropathy and may provide a foundation for development of MR protocols for early detection of degenerative and neoplastic diseases. PMID:25010068

  16. Inversion recovery ultrashort echo time magnetic resonance imaging: A method for simultaneous direct detection of myelin and high signal demonstration of iron deposition in the brain - A feasibility study.

    PubMed

    Sheth, Vipul R; Fan, Shujuan; He, Qun; Ma, Yajun; Annese, Jacopo; Switzer, Robert; Corey-Bloom, Jody; Bydder, Graeme M; Du, Jiang

    2017-05-01

    Multiple sclerosis (MS) causes demyelinating lesions in the white matter and increased iron deposition in the subcortical gray matter. Myelin protons have an extremely short T2* (<1ms) and are not directly detected with conventional clinical magnetic resonance (MR) imaging sequences. Iron deposition also reduces T2*, leading to reduced signal on clinical sequences. In this study we tested the hypothesis that the inversion recovery ultrashort echo time (IR-UTE) pulse sequence can directly and simultaneously image myelin and iron deposition using a clinical 3T scanner. The technique was first validated on a synthetic myelin phantom (myelin powder in D2O) and a Feridex iron phantom. This was followed by studies of cadaveric MS specimens, healthy volunteers and MS patients. UTE imaging of the synthetic myelin phantom showed an excellent bi-component signal decay with two populations of protons, one with a T2* of 1.2ms (residual water protons) and the other with a T2* of 290μs (myelin protons). IR-UTE imaging shows sensitivity to a wide range of iron concentrations from 0.5 to ~30mM. The IR-UTE signal from white matter of the brain of healthy volunteers shows a rapid signal decay with a short T2* of ~300μs, consistent with the T2* values of myelin protons in the synthetic myelin phantom. IR-UTE imaging in MS brain specimens and patients showed multiple white matter lesions as well as areas of high signal in subcortical gray matter. This in specimens corresponded in position to Perl's diaminobenzide staining results, consistent with increased iron deposition. IR-UTE imaging simultaneously detects lesions with myelin loss in the white matter and iron deposition in the gray matter. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Transverse texture and microstructure gradients in friction-stir welded 2519 aluminum.

    SciTech Connect

    Bingert, J. F.; Fonda, R. W.

    2003-01-01

    Friction-stir welding produces severe thermomechanical transients that generate crystallographic texture evolution throughout the weld-affected microstructure . In this study, a friction stir weld in a coarse-grained 2519 aluminum plate was investigated in order to resolve the influence of these thermal and deformation effects on texture and microstructure development . Automated electron backscatter diffraction (EBSD) was applied to spatially resolve orientations in the base metal, weld nugget, and thermomechanical and heat-affected zones. Results show a gradient demarcated by an alteration in boundary character, texture, and precipitate distribution between the thermomechanical affected zone and the recrystallized weld nugget . EBSD scans and microstructural characterizations reveal substructure evolution from the base plate to the nugget indicative of dynamic recovery and recrystallization processes . Experimental results of texture evolution, however, did not directly follow from considerations of simplified deformation gradients and resultant simple shear textures resulting from restricted glide .

  18. Friction stir processing on carbon steel

    SciTech Connect

    Tarasov, Sergei Yu.; Melnikov, Alexander G.; Rubtsov, Valery E.

    2014-11-14

    Friction stir processing of medium carbon steel samples has been carried out using a milling machine and tools made of cemented tungsten carbide. Samples have been machined from 40 and 40X steels. The tools have been made in the shape of 5×5×1.5 mm and 3×3×1.5 mm tetrahedrons. The microstructure of stirred zone has been obtained using the smaller tool and consists of fine recrystallized 2-3 μm grains, whereas the larger tool has produced the 'onion-like' structures comprising hard quenched 'white' 500-600 MPa layers with 300-350 MPa interlayers of bainite needles. The mean values of wear intensity obtained after measuring the wear scar width were 0.02 mm/m and 0.001 mm/m for non-processed and processed samples, respectively.

  19. Microstructure characterization of the stir zone of submerged friction stir processed aluminum alloy 2219

    SciTech Connect

    Feng, Xiuli; Liu, Huijie; Lippold, John C.

    2013-08-15

    Aluminum alloy 2219-T6 was friction stir processed using a novel submerged processing technique to facilitate cooling. Processing was conducted at a constant tool traverse speed of 200 mm/min and spindle rotation speeds in the range from 600 to 800 rpm. The microstructural characteristics of the base metal and processed zone, including grain structure and precipitation behavior, were studied using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness maps were constructed on polished cross sections of as-processed samples. The effect of tool rotation speed on the microstructure and hardness of the stir zone was investigated. The average grain size of the stir zone was much smaller than that of the base metal, but the hardness was also lower due to the formation of equilibrium θ precipitates from the base metal θ′ precipitates. Stir zone hardness was found to decrease with increasing rotation speed (heat input). The effect of processing conditions on strength (hardness) was rationalized based on the competition between grain refinement strengthening and softening due to precipitate overaging. - Highlights: • SZ grain size (∼ 1 μm) is reduced by over one order of magnitude relative to the BM. • Hardness in the SZ is lower than that of the precipitation strengthened BM. • Metastable θ′ in the base metal transforms to equilibrium θ in the stir zone. • Softening in the SZ results from a decrease of precipitation strengthening.

  20. Magnesium Based Composite via Friction Stir Processing

    DTIC Science & Technology

    2013-04-01

    process developed by Mishra et.al [8] based on the principles of friction stir welding ( FSW ) is getting increased attention. It involves the traverse...compared to other thermomechanical processes [9]. Mishra et al. [10] have used FSP to fabricate a surface composite with SiC particulates in aluminum ...This work was followed by other reports of composite fabrication in aluminum alloys with various reinforcements, like Al3Ti, Al2Cu, Al2O3

  1. Ultrasonic stir welding process and apparatus

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2009-01-01

    An ultrasonic stir welding device provides a method and apparatus for elevating the temperature of a work piece utilizing at least one ultrasonic heater. Instead of relying on a rotating shoulder to provide heat to a workpiece an ultrasonic heater is utilized to provide ultrasonic energy to the workpiece. A rotating pin driven by a motor assembly performs the weld on the workpiece. A handheld version can be constructed as well as a fixedly mounted embodiment.

  2. Flexible Hybrid Friction Stir Joining Technology

    SciTech Connect

    2008-12-01

    This factsheet describes a research project whose goal is to advance the friction stir welding (FSW) process as a manufacturing technology that can be deployed for on-site construction of large, complex and typically thick-sectioned structures made of high performance and high-temperature materials. This would transform FSW from a specialty joining process into one with pervasive application potential across a number of industrial sectors where the payoff of energy reduction, environmental and economic benefits would be significant.

  3. Fuel property effects in stirred combustors

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Soot formation in strongly backmixed combustion was investigated using the jet-stirred combustor (JSC). This device provided a combustion volume in which temperature and combustion were uniform. It simulated the recirculating characteristics of the gas turbine primary zone; it was in this zone where mixture conditions were sufficiently rich to produce soot. Results indicate that the JSC allows study of soot formation in an aerodynamic situation revelant to gas turbines.

  4. Eddy stirring in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Naveira Garabato, A. C.; Ferrari, R.; Polzin, K. L.

    2011-09-01

    There is an ongoing debate concerning the distribution of eddy stirring across the Antarctic Circumpolar Current (ACC) and the nature of its controlling processes. The problem is addressed here by estimating the isentropic eddy diffusivity κ from a collection of hydrographic and altimetric observations, analyzed in a mixing length theoretical framework. It is shown that, typically, κ is suppressed by an order of magnitude in the upper kilometer of the ACC frontal jets relative to their surroundings, primarily as a result of a local reduction of the mixing length. This observation is reproduced by a quasi-geostrophic theory of eddy stirring across a broad barotropic jet based on the scaling law derived by Ferrari and Nikurashin (2010). The theory interprets the observed widespread suppression of the mixing length and κ in the upper layers of frontal jets as the kinematic consequence of eddy propagation relative to the mean flow within jet cores. Deviations from the prevalent regime of mixing suppression in the core of upper-ocean jets are encountered in a few special sites. Such `leaky jet' segments appear to be associated with sharp stationary meanders of the mean flow that are generated by the interaction of the ACC with major topographic features. It is contended that the characteristic thermohaline structure of the Southern Ocean, consisting of multiple upper-ocean thermohaline fronts separated and underlaid by regions of homogenized properties, is largely a result of the widespread suppression of eddy stirring by parallel jets.

  5. Stir bar sorptive extraction for trace analysis.

    PubMed

    David, Frank; Sandra, Pat

    2007-06-08

    Stir bar sorptive extraction (SBSE) was introduced in 1999 as a solventless sample preparation method for the extraction and enrichment of organic compounds from aqueous matrices. The method is based on sorptive extraction, whereby the solutes are extracted into a polymer coating on a magnetic stirring rod. The extraction is controlled by the partitioning coefficient of the solutes between the polymer coating and the sample matrix and by the phase ratio between the polymer coating and the sample volume. For a polydimethylsiloxane coating and aqueous samples, this partitioning coefficient resembles the octanol-water partitioning coefficient. In comparison to solid phase micro-extraction, a larger amount of sorptive extraction phase is used and consequently extremely high sensitivities can be obtained as illustrated by several successful applications in trace analysis in environmental, food and biomedical fields. Initially SBSE was mostly used for the extraction of compounds from aqueous matrices. The technique has also been applied in headspace mode for liquid and solid samples and in passive air sampling mode. In this review article, the principles of stir bar sorptive extraction are described and an overview of SBSE applications is given.

  6. Improved border sharpness of post-infarct scar by a novel self-navigated free-breathing high-resolution 3D whole-heart inversion recovery magnetic resonance approach.

    PubMed

    Rutz, Tobias; Piccini, Davide; Coppo, Simone; Chaptinel, Jerome; Ginami, Giulia; Vincenti, Gabriella; Stuber, Matthias; Schwitter, Juerg

    2016-12-01

    The border zone of post-infarction myocardial scar as identified by late gadolinium enhancement (LGE) has been identified as a substrate for arrhythmias and consequently, high-resolution 3D scar information is potentially useful for planning of electrophysiological interventions. This study evaluates the performance of a novel high-resolution 3D self-navigated free-breathing inversion recovery magnetic resonance pulse sequence (3D-SN-LGE) vs. conventional 2D breath-hold LGE (2D-LGE) with regard to sharpness of borders (SBorder) of post-infarction scar. Patients with post-infarction scar underwent two magnetic resonance examinations for conventional 2D-LGE and high-resolution 3D-SN-LGE acquisitions (both 15 min after 0.2 mmol/kg Gadobutrol IV) at 1.5T. In the prototype 3D-SN-LGE sequence, each ECG-triggered radial steady-state-free-precession read-out segment is preceded by a non-slice-selective inversion pulse. Scar volume and SBorder were assessed on 2D-LGE and matching reconstructed high-resolution 3D-SN-LGE short-axis slices. In 16 patients (four females, 58 ± 10y) all scars visualized by 2D-LGE could be identified on 3D-SN-LGE (time between 2D-LGE and 3D-SN-LGE 48 ± 53 days). A good agreement of scar volume by 3D-SN-LGE vs. 2D-LGE was found (Bland-Altman: -3.7 ± 3.4 ml, correlation: r = 0.987, p < 0.001) with a small difference in scar volume (20.5 (15.8, 35.2) ml vs. 24.5 (20.0, 41.9)) ml, respectively, p = 0.002] and a good intra- and interobserver variability (1.1 ± 4.1 and -1.1 ± 11.9 ml, respectively). SBorder of border "scar to non-infarcted myocardium" was superior on 3D-SN-LGE vs. 2D-LGE: 0.180 ± 0.044 vs. 0.083 ± 0.038, p < 0.001. Detection and quantification of myocardial scar by 3D-SN-LGE is feasible and accurate in comparison to 2D-LGE. The high spatial resolution of the 3D sequence improves delineation of scar borders.

  7. Stirring effects in models of oceanic plankton populations

    NASA Astrophysics Data System (ADS)

    Neufeld, Zoltan

    2012-09-01

    We present an overview and extend previous results on the effects of large scale oceanic transport processes on plankton population dynamics, considering different types of ecosystem models. We find that increasing stirring rate in an environment where the carrying capacity is non-uniformly distributed leads to an overall decrease of the effective carrying capacity of the system. This may lead to sharp regime shifts induced by stirring in systems with multiple steady states. In prey-predator type systems, stirring leads to resonant response of the population dynamics to fluctuations enhancing the spatial variability—patchiness—in a certain range of stirring rates. Oscillatory population models produce strongly heterogeneous patchy distribution of plankton blooms when the stirring is weak, while strong stirring may either synchronise the oscillatory dynamics, when the inhomogeneity is relatively weak, or suppress oscillations completely (oscillator death) by reducing the effective carrying capacity below the bifurcation point.

  8. Stirring effects in models of oceanic plankton populations.

    PubMed

    Neufeld, Zoltan

    2012-09-01

    We present an overview and extend previous results on the effects of large scale oceanic transport processes on plankton population dynamics, considering different types of ecosystem models. We find that increasing stirring rate in an environment where the carrying capacity is non-uniformly distributed leads to an overall decrease of the effective carrying capacity of the system. This may lead to sharp regime shifts induced by stirring in systems with multiple steady states. In prey-predator type systems, stirring leads to resonant response of the population dynamics to fluctuations enhancing the spatial variability-patchiness-in a certain range of stirring rates. Oscillatory population models produce strongly heterogeneous patchy distribution of plankton blooms when the stirring is weak, while strong stirring may either synchronise the oscillatory dynamics, when the inhomogeneity is relatively weak, or suppress oscillations completely (oscillator death) by reducing the effective carrying capacity below the bifurcation point.

  9. Corrosion Behavior of Friction Stir Welded High Strength Aluminum Alloys

    DTIC Science & Technology

    2002-01-18

    Angelo Guinasso, " Stress Corrosion Susceptibility in 7050 -T751 Aluminum Following Friction Stir Welding", Proc. First Friction Stir Welding Symposium...potential of the nugget. Susceptibility to stress corrosion cracking (SCC) was evaluated using the slow strain rate (SSR) method described in ASTM Standards...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP015941 TITLE: Corrosion Behavior of Friction Stir Welded High Strength

  10. Inverse Floatation

    NASA Astrophysics Data System (ADS)

    Nath, Saurabh; Mukherjee, Anish; Chatterjee, Souvick; Ganguly, Ranjan; Sen, Swarnendu; Mukhopadhyay, Achintya; Boreyko, Jonathan

    2014-11-01

    We have observed that capillarity forces may cause floatation in a few non-intuitive configurations. These may be divided into 2 categories: i) floatation of heavier liquid droplets on lighter immiscible ones and ii) fully submerged floatation of lighter liquid droplets in a heavier immiscible medium. We call these counter-intuitive because of the inverse floatation configuration. For case (i) we have identified and studied in detail the several factors affecting the shape and maximum volume of the floating drop. We used water and vegetable oil combinations as test fluids and established the relation between Bond Number and maximum volume contained in a floating drop (in the order of μL). For case (ii), we injected vegetable oil drop-wise into a pool of water. The fully submerged configuration of the drop is not stable and a slight perturbation to the system causes the droplet to burst and float in partially submerged condition. Temporal variation of a characteristic length of the droplet is analyzed using MATLAB image processing. The constraint of small Bond Number establishes the assumption of lubrication regime in the thin gap. A brief theoretical formulation also shows the temporal variation of the gap thickness. Jadavpur University, Jagadis Bose Centre of Excellence, Virginia Tech.

  11. Pediatric and adolescent lymphoma: comparison of whole-body STIR half-Fourier RARE MR imaging with an enhanced PET/CT reference for initial staging.

    PubMed

    Punwani, Shonit; Taylor, Stuart A; Bainbridge, Alan; Prakash, Vineet; Bandula, Steven; De Vita, Enrico; Olsen, Oystein E; Hain, Sharon F; Stevens, Nicola; Daw, Stephen; Shankar, Ananth; Bomanji, Jamshed B; Humphries, Paul D

    2010-04-01

    To compare the diagnostic performance of rapid whole-body anatomic magnetic resonance (MR) staging of pediatric and adolescent lymphoma to an enhanced positron emission tomographic (PET)/computed tomographic (CT) reference standard. Ethical permission was given by the University College London Hospital ethics committee, and informed written consent was obtained from all participants and/or parents or guardians. Thirty-one subjects (age range, 7.3-18.0 years; 18 male, 11 female) with histologically proved lymphoma were prospectively recruited. Pretreatment staging was performed with whole-body short inversion time inversion-recovery (STIR) half-Fourier rapid acquisition with relaxation enhancement (RARE) MR imaging, fluorine 18 fluorodeoxyglucose PET/CT, and contrast agent-enhanced chest CT. Twenty-six subjects had posttreatment PET/CT and compromised our final cohort. Eleven nodal and 11 extranodal sites per patient were assessed on MR imaging by two radiologists in consensus, with a nodal short-axis threshold of >1 cm and predefined extranodal positivity criteria. The same sites were independantly evaluated by two nuclear medicine physicians on PET/CT images. Disease positivity was defined as a maximum standardized uptake value >2.5 or nodal size >1 cm. An unblinded expert panel reevaluated the imaging findings, removing perceptual errors, and derived an enhanced PET/CT reference standard (taking into account chest CT and 3-month follow-up imaging) against which the reported and intrinsic performance of MR imaging was assessed by using the kappa statistic. There was very good agreement between MR imaging and the enhanced PET/CT reference standard for nodal and extranodal staging (kappa = 0.96 and 0.86, respectively) which improved following elimination of perceptual errors (kappa = 0.97 and 0.91, respectively). The sensitivity and specificity of MR imaging (following removal of perceptual error) were 98% and 99%, respectively, for nodal disease and 91% and 99

  12. Tool For Friction Stir Tack Welding of Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Bjorkman, Gerald W.; Dingler, Johnny W.; Loftus, Zachary

    2003-01-01

    A small friction-stir-welding tool has been developed for use in tack welding of aluminum-alloy workpieces. It is necessary to tack-weld the workpieces in order to hold them together during friction stir welding because (1) in operation, a full-size friction-stir-welding tool exerts a large force that tends to separate the workpieces and (2) clamping the workpieces is not sufficient to resist this force. It is possible to tack the pieces together by gas tungsten arc welding, but the process can be awkward and time-consuming and can cause sufficient damage to necessitate rework. Friction stir tack welding does not entail these disadvantages. In addition, friction stir tack welding can be accomplished by use of the same automated equipment (except for the welding tool) used in subsequent full friction stir welding. The tool for friction stir tack welding resembles the tool for full friction stir welding, but has a narrower shoulder and a shorter pin. The shorter pin generates a smaller workpiece-separating force so that clamping suffices to keep the workpieces together. This tool produces a continuous or intermittent partial-penetration tack weld. The tack weld is subsequently consumed by action of the larger tool used in full friction stir welding tool.

  13. Trace determination of volatile polycyclic aromatic hydrocarbons in natural waters by magnetic ionic liquid-based stir bar dispersive liquid microextraction.

    PubMed

    Benedé, Juan L; Anderson, Jared L; Chisvert, Alberto

    2018-01-01

    In this work, a novel hybrid approach called stir bar dispersive liquid microextraction (SBDLME) that combines the advantages of stir bar sorptive extraction (SBSE) and dispersive liquid-liquid microextraction (DLLME) has been employed for the accurate and sensitive determination of ten polycyclic aromatic hydrocarbons (PAHs) in natural water samples. The extraction is carried out using a neodymium stir bar magnetically coated with a magnetic ionic liquid (MIL) as extraction device, in such a way that the MIL is dispersed into the solution at high stirring rates. Once the stirring is ceased, the MIL is magnetically retrieved onto the stir bar, and subsequently subjected to thermal desorption (TD) coupled to a gas chromatography-mass spectrometry (GC-MS) system. The main parameters involved in TD, as well as in the extraction step affecting the extraction efficiency (i.e., MIL amount, extraction time and ionic strength) were evaluated. Under the optimized conditions, the method was successfully validated showing good linearity, limits of detection and quantification in the low ng L(-1) level, good intra- and inter-day repeatability (RSD < 13%) and good enrichment factors (18 - 717). This sensitive analytical method was applied to the determination of trace amounts of PAHs in three natural water samples (river, tap and rainwater) with satisfactory relative recovery values (84-115%), highlighting that the matrices under consideration do not affect the extraction process. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Friction-Stir-Welded and Spin-Formed End Domes for Cryogenic Tanks

    NASA Technical Reports Server (NTRS)

    Hales, S. J.; Tayon, W. A.; Domack, M. S.

    2012-01-01

    Manufacturing of single-piece end domes for cryogenic tanks employing spin forming of tailored, friction-stir-welded blanks of Al-Li alloy 2195 plate offers cost and reliability benefits. The introduction of plastic deformation into a friction stir weld is a unique feature of the proposed manufacturing route. This investigation addressed abnormal grain growth [AGG] within the friction stir weldments during postfabrication processing of a prototype dome. The phenomenon of AGG was observed during the solution heat treatment [SHT] phase of T8 tempering and is a major concern for meeting specifications. Such abrupt microstructural transitions can be detrimental to notch-sensitive mechanical properties, such as ductility and/or fracture toughness. If the issue of AGG cannot be resolved, then the acceptance of this approach as a viable manufacturing route may be in jeopardy. The innovative approach adopted in this investigation was the insertion of a stand-alone, Intermediate Annealing Treatment [IAT] between the spin forming and T8 processing operations. A simple, recovery annealing step was deemed to be the most readily-scalable solution when fabricating thin-walled, ellipsoidal domes. The research effort culminated in the development of an effective IAT, which resulted in a significant decrease in AGG following SHT. The processing philosophy adopted in designing the IAT is outlined and the microstructural reasons for success are discussed. The analytical results presented are consistent with promoting continuous grain growth during the IAT, thereby suppressing AGG during the SHT.

  15. Development and application of novel clonazepam molecularly imprinted coatings for stir bar sorptive extraction.

    PubMed

    Li, Xiaoxu; Mei, Xiaoliang; Xu, Lei; Shen, Xin; Zhu, Wanying; Hong, Junli; Zhou, Xuemin

    2016-04-15

    The molecularly imprinted magnetic stir bar coatings were created based on graft-functional Fe3O4 nanoparticles with magnetic field-induced self-assembly. The magnetic complex including clonazepam as template, the graft-functional Fe3O4 nanoparticles and methacrylic acid as monomers was pre-assembled through π-π interaction and hydrogen bonding, then was directionally adsorbed on the surface of magnetic stir bar under the magnetic induction. The molecularly imprinted coating with well-ordered structure was generated by one-step copolymerization based on the cross linking of ethylene glycol dimethacrylate. The molecularly imprinted coating with multiple recognition sites could be manufactured and applied in polar solvents, and showed superior selectivity and fast binding kinetics for benzodiazepines. The analytes in herbal health foods, treated by stir bar sorptive extraction, were determined by HPLC-UV. Good linearity was observed in the range of 0.01-2 μg mL(-1). The content of clonazepam in the herbal health foods was found to be 44 ng g(-1), and the average recoveries were 89.8-103.3% with a relative standard deviation (RSD) <6.5%, demonstrating the successful application in real sample analysis.

  16. Automated multisyringe stir bar sorptive extraction using robust montmorillonite/epoxy-coated stir bars.

    PubMed

    Ghani, Milad; Saraji, Mohammad; Maya, Fernando; Cerdà, Víctor

    2016-05-06

    Herein we present a simple, rapid and low cost strategy for the preparation of robust stir bar coatings based on the combination of montmorillonite with epoxy resin. The composite stir bar was implemented in a novel automated multisyringe stir bar sorptive extraction system (MS-SBSE), and applied to the extraction of four chlorophenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) as model compounds, followed by high performance liquid chromatography-diode array detection. The different experimental parameters of the MS-SBSE, such as sample volume, selection of the desorption solvent, desorption volume, desorption time, sample solution pH, salt effect and extraction time were studied. Under the optimum conditions, the detection limits were between 0.02 and 0.34μgL(-1). Relative standard deviations (RSD) of the method for the analytes at 10μgL(-1) concentration level ranged from 3.5% to 4.1% (as intra-day RSD) and from 3.9% to 4.3% (as inter-day RSD at 50μgL(-1) concentration level). Batch-to-batch reproducibility for three different stir bars was 4.6-5.1%. The enrichment factors were between 30 and 49. In order to investigate the capability of the developed technique for real sample analysis, well water, wastewater and leachates from a solid waste treatment plant were satisfactorily analyzed.

  17. Friction Stir Weld Modeling at MSFC: Kinematics

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2000-01-01

    A "merry-go-round" computation model makes it easier to visualize how tracer experiments of varied sorts (chemical, shot, wire) are consistent with a "moving plug model" of flow around the friction stir welding pin-tool. The moving plug model comprises a twofold flow: 1. a primary rotation of a plug of metal with the tool, which moves metal around the tool by wiping it on and off the plug, and 2. a secondary, relatively slow circulation induced by the threads on the tool resembling a circular vortex ring around the tool.

  18. Gas fluidized-bed stirred media mill

    DOEpatents

    Sadler, III, Leon Y.

    1997-01-01

    A gas fluidized-bed stirred media mill is provided for comminuting solid ticles. The mill includes a housing enclosing a porous fluidizing gas diffuser plate, a baffled rotor and stator, a hollow drive shaft with lateral vents, and baffled gas exhaust exit ports. In operation, fluidizing gas is forced through the mill, fluidizing the raw material and milling media. The rotating rotor, stator and milling media comminute the raw material to be ground. Small entrained particles may be carried from the mill by the gas through the exit ports when the particles reach a very fine size.

  19. Effect of Electromagnetic Stirring on Weld Pools.

    DTIC Science & Technology

    1983-10-01

    Cminue an reverse sde If neceewer mE identity b block nmber) GTAW Electromagnetic Agitation Titanium Thermal Gradient 20. A RACT (Continue en revers... GTAW Gas Tungsten Arc Welding V Voltage iv -- ’ -’y - -’ e - a + . - - . - CONVERSION FACTORS 1 -1/sin - 2.12 cfh I J - 5 (9F - 32) 1 cm - 0.394 in...carefully controlled and monitored conditions. The set of welds made to determine the effect of stirring frequency on grain size employed automated GTAW

  20. Forming of aluminium alloy friction stir welds

    NASA Astrophysics Data System (ADS)

    Bruni, Carlo

    2016-10-01

    The present paper aims at investigating, through analytical models, numerical models and experiments, the effect of the warm deformation phase, realised with an in temperature upsetting, on the weld previously performed by friction stir lap welding on aluminium alloy blanks. The investigation allows to show the deformation zones after upsetting that determine the homogenisation of the weld section. The analytical model allows to relate the friction factor with the upsetting load. The presence on the weld of not elevated friction factor values determines the deformation and localisation levels very useful for the weld. Such methodology allows to improve the weld itself with the forming phase.

  1. Marine ecosystem dynamics, ocean circulation and horizontal stirring

    NASA Astrophysics Data System (ADS)

    Rossi, V.; Tewkai, E.; López, C.; Sudre, J.; Hernández-García, E.; Garcon, V.

    2009-04-01

    The oceanic submeso and mesoscale circulation and its eddies, filaments, meanders play a major role in marine ecosystems dynamics from the lower trophic levels to the marine top predators. We study here the interplay between turbulence in fluid dynamics on these scales and biological activity at different trophic levels using two cases study. The first example focuses on the four eastern boundary upwelling zones, the Canary, Benguela, California and Humboldt upwelling systems which constitute the largest contribution to the world ocean productivity. These areas are spatially heterogeneous, populated with a large variety of mesoscale and sub-mesoscale structures such as filaments, plumes and eddies, which control exchange processes between the shelf and open ocean and play a major role in modulating the biomass, rates and structure of marine ecosystems. We will present here results from a lagrangian approach based on Finite Size Lyapunov Exponents (FSLE) using altimetric and scatterometric data to estimate the spatial and temporal variations in the lateral stirring and mixing of tracers in the upper ocean within the four areas. When investigating links with chlorophyll a concentration as a proxy for biological activity in these upwelling systems, results show that surface horizontal stirring and mixing vary inversely with chlorophyll standing stocks. FSLEs lead to a clear clustering of the systems suggesting that one may use them as integrated and comparative indices for characterizing horizontal dynamical features in all eastern boundary upwellings. Then we investigate the role of submesoscale structures in the Mozambique Channel on the distribution of a top marine predator, the Great Frigatebird. Using similar dynamical concept, the FSLE, we have identified Lagrangian Coherent Structures (LCSs) present in the surface flow in the Channel. By comparing seabirds' satellite positions with LCSs locations, we demonstrate that frigatebirds track precisely these

  2. Microstructural characterization in dissimilar friction stir welding between 304 stainless steel and st37 steel

    SciTech Connect

    Jafarzadegan, M.; Feng, A.H.; Abdollah-zadeh, A.; Saeid, T.; Shen, J.; Assadi, H.

    2012-12-15

    In the present study, 3 mm-thick plates of 304 stainless steel and st37 steel were welded together by friction stir welding at a welding speed of 50 mm/min and tool rotational speed of 400 and 800 rpm. X-ray diffraction test was carried out to study the phases which might be formed in the welds. Metallographic examinations, and tensile and microhardness tests were used to analyze the microstructure and mechanical properties of the joint. Four different zones were found in the weld area except the base metals. In the stir zone of the 304 stainless steel, a refined grain structure with some features of dynamic recrystallization was evidenced. A thermomechanically-affected zone was characterized on the 304 steel side with features of dynamic recovery. In the other side of the stir zone, the hot deformation of the st37 steel in the austenite region produced small austenite grains and these grains transformed to fine ferrite and pearlite and some products of displacive transformations such as Widmanstatten ferrite and martensite by cooling the material after friction stir welding. The heat-affected zone in the st37 steel side showed partially and fully refined microstructures like fusion welding processes. The recrystallization in the 304 steel and the transformations in the st37 steel enhanced the hardness of the weld area and therefore, improved the tensile properties of the joint. - Highlights: Black-Right-Pointing-Pointer FSW produced sound welds between st37 low carbon steel and 304 stainless steel. Black-Right-Pointing-Pointer The SZ of the st37 steel contained some products of allotropic transformation. Black-Right-Pointing-Pointer The material in the SZ of the 304 steel showed features of dynamic recrystallization. Black-Right-Pointing-Pointer The finer microstructure in the SZ increased the hardness and tensile strength.

  3. Friction stir method for forming structures and materials

    DOEpatents

    Feng, Zhili; David, Stan A.; Frederick, David Alan

    2011-11-22

    Processes for forming an enhanced material or structure are disclosed. The structure typically includes a preform that has a first common surface and a recess below the first common surface. A filler is added to the recess and seams are friction stir welded, and materials may be stir mixed.

  4. Certification of a weld produced by friction stir welding

    DOEpatents

    Obaditch, Chris; Grant, Glenn J

    2013-10-01

    Methods, devices, and systems for providing certification of friction stir welds are disclosed. A sensor is used to collect information related to a friction stir weld. Data from the sensor is compared to threshold values provided by an extrinsic standard setting organizations using a certification engine. The certification engine subsequently produces a report on the certification status of the weld.

  5. Damage Tolerance Behavior of Friction Stir Welds in Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process used in the fabrication of various aerospace structures. Self-reacting and conventional friction stir welding are variations of the friction stir weld process employed in the fabrication of cryogenic propellant tanks which are classified as pressurized structure in many spaceflight vehicle architectures. In order to address damage tolerance behavior associated with friction stir welds in these safety critical structures, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data describing fracture behavior, residual strength capability, and cyclic mission life capability of friction stir welds at ambient and cryogenic temperatures have been generated and will be presented in this paper. Fracture behavior will include fracture toughness and tearing (R-curve) response of the friction stir welds. Residual strength behavior will include an evaluation of the effects of lack of penetration on conventional friction stir welds, the effects of internal defects (wormholes) on self-reacting friction stir welds, and an evaluation of the effects of fatigue cycled surface cracks on both conventional and selfreacting welds. Cyclic mission life capability will demonstrate the effects of surface crack defects on service load cycle capability. The fracture data will be used to evaluate nondestructive inspection and proof test requirements for the welds.

  6. A Rotating Plug Model of Friction Stir Welding Heat Transfer

    NASA Technical Reports Server (NTRS)

    Raghulapadu J. K.; Peddieson, J.; Buchanan, G. R.; Nunes, A. C.

    2006-01-01

    A simplified rotating plug model is employed to study the heat transfer phenomena associated with the fiction stir welding process. An approximate analytical solution is obtained based on this idealized model and used both to demonstrate the qualitative influence of process parameters on predictions and to estimate temperatures produced in typical fiction stir welding situations.

  7. Friction Stir Welding of Lightweight Vehicle Structures: Final Report

    SciTech Connect

    Sanella, M L

    2008-08-31

    The purpose of this Cooperative Research and Development Agreement (CRADA) between UTBattelle, LLC and Ford Motor Company was to establish friction stir welding (FSW) and friction stir processing as viable options for use in construction of lightweight substructures for trucks and cars, including engine cradles, suspension sub frames, instrument panel supports, and intake manifolds.

  8. Flow Patterns During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Guerra, M.; Schmidt, C.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Friction Stir Welding is a relatively new technique for welding that uses a cylindrical pin or nib inserted along the weld seam. The nib (usually threaded) and the shoulder in which it is mounted are rapidly rotated and advanced along the seam. Extreme deformation takes place leaving a fine equiaxed structure in the weld region., The flow of metal during Friction Stir Welding is investigated using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes. The first is a wiping of material from the advancing front side of the nib onto a zone of material that rotates and advances with the nib. The material undergoes a helical motion within the rotational zone that both rotates and advances and descends in the wash of the threads on the nib and rises on the outer part of the rotational zone. After one or more rotations, this material is sloughed off in its wake of the nib, primarily on the advancing side. The second process is an entrainment of material from the front retreating side of the nib that fills in between the sloughed off pieces from the advancing side.

  9. Friction Stir Welding at MSFC: Kinematics

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.

    2001-01-01

    In 1991 The Welding Institute of the United Kingdom patented the Friction Stir Welding (FSW) process. In FSW a rotating pin-tool is inserted into a weld seam and literally stirs the faying surfaces together as it moves up the seam. By April 2000 the American Welding Society International Welding and Fabricating Exposition featured several exhibits of commercial FSW processes and the 81st Annual Convention devoted a technical session to the process. The FSW process is of interest to Marshall Space Flight Center (MSFC) as a means of avoiding hot-cracking problems presented by the 2195 aluminum-lithium alloy, which is the primary constituent of the Lightweight Space Shuttle External Tank. The process has been under development at MSFC for External Tank applications since the early 1990's. Early development of the FSW process proceeded by cut-and-try empirical methods. A substantial and complex body of data resulted. A theoretical model was wanted to deal with the complexity and reduce the data to concepts serviceable for process diagnostics, optimization, parameter selection, etc. A first step in understanding the FSW process is to determine the kinematics, i.e., the flow field in the metal in the vicinity of the pin-tool. Given the kinematics, the dynamics, i.e., the forces, can be targeted. Given a completed model of the FSW process, attempts at rational design of tools and selection of process parameters can be made.

  10. New Tool Creates a Big Stir

    NASA Technical Reports Server (NTRS)

    2001-01-01

    A new self-adjusting, retractable pin tool for friction stir welding is now used in the manufacturing of components for NASA Space Shuttles. Friction stir welding is a process that makes straight-line welds without bringing the parent material to a liquid state. This is accomplished through high-speed rotation, which generates frictional heat between the welding tool and the piece being welded. This heat causes the material to soften to the point of plasticity without allowing it to melt. The plasticized material is then transferred from the front edge of the welding tool to the trail edge, where it joins the pieces being welded. However, a major flaw of this method is its reliance on a single-piece pin tool. The weld is left unfinished and a hole remains where the pin was inserted. The hole must be covered with a rivet in order to preserve the integrity of the weld. The NASA-developed pin tool, however, eliminates the need for this finishing step, as its retraction allows continuous rewelding at lesser depths, until the hole is completely closed. With this NASA technology, welding of higher strength alloys, as well as non-planer and variable thickness structures can be achieved.

  11. The Plunge Phase of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur; McClure, John; Avila, Ricardo

    2005-01-01

    Torque and plunge force during the initial plunge phase in Friction Stir Welding were measured for a 0.5 inch diameter pin entering a 2219 aluminum alloy plate. Weld structures were preserved for metallographic observation by making emergency stops at various plunge depths. The plunging pin tool is seen to be surrounded by a very fine grained layer of recrystallized metal extending substantially below the bottom of the pin, implying a shear interface in the metal below and not at the tool-metal interface. Torque and plunge force during the initial plunge phase in Friction Stir Welding are calculated from a straight forward model based on a concept to plastic flow in the vicinity of the plunging tool compatible with structural observations. The concept: a disk of weld metal seized to and rotating with the bottom of the pin is squeezed out laterally by the plunge force and extruded upwards in a hollow cylinder around the tool. As the shear surface separating rotating disk from stationary weld metal engulfs fresh metal, the fresh metal is subjected to severe shear deformation, which results in its recrystallization. Encouraging agreement between computations and measured torque and plunge force is obtained.

  12. The Plunge Phase of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur; McClure, John; Avila, Ricardo

    2005-01-01

    Torque and plunge force during the initial plunge phase in Friction Stir Welding were measured for a 0.5 inch diameter pin entering a 2219 aluminum alloy plate. Weld structures were preserved for metallographic observation by making emergency stops at various plunge depths. The plunging pin tool is seen to be surrounded by a very fine grained layer of recrystallized metal extending substantially below the bottom of the pin, implying a shear interface in the metal below and not at the tool-metal interface. Torque and plunge force during the initial plunge phase in Friction Stir Welding are calculated from a straight forward model based on a concept to plastic flow in the vicinity of the plunging tool compatible with structural observations. The concept: a disk of weld metal seized to and rotating with the bottom of the pin is squeezed out laterally by the plunge force and extruded upwards in a hollow cylinder around the tool. As the shear surface separating rotating disk from stationary weld metal engulfs fresh metal, the fresh metal is subjected to severe shear deformation, which results in its recrystallization. Encouraging agreement between computations and measured torque and plunge force is obtained.

  13. Improving the Quality of Protein Crystals Using Stirring Crystallization

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroaki; Matsumura, Hiroyoshi; Niino, Ai; Takano, Kazufumi; Kinoshita, Takayoshi; Warizaya, Masaichi; Inoue, Tsuyoshi; Mori, Yusuke; Sasaki, Takatomo

    2004-04-01

    Recent reports state that a high magnetic field improves the crystal quality of bovine adenosine deaminase (ADA) with an inhibitor [Kinoshita et al.: Acta Cryst. D59 (2003) 1333]. In this paper, we examine the effect of stirring solution on ADA crystallization using a vapor-diffusion technique with rotary and figure-eight motion shakers. The probability of obtaining high-quality crystals is increased with stirring in a figure-eight pattern. Furthermore, rotary stirring greatly increased the probability of obtaining high-quality crystals, however, nucleation time was also increased. The crystal structure with the inhibitor was determined at a high resolution using a crystal obtained from a stirred solution. These results indicate that stirring with simple equipment is as useful as the high magnetic field technique for protein crystallization.

  14. High-Powered, Ultrasonically Assisted Thermal Stir Welding

    NASA Technical Reports Server (NTRS)

    Ding, Robert

    2013-01-01

    This method is a solid-state weld process capable of joining metallic alloys without melting. The weld workpieces to be joined by thermal stir welding (TSW) are drawn, by heavy forces, between containment plates past the TSW stir tool that then causes joining of the weld workpiece. TSW is similar to friction stir welding (FSW) in that material is heated into a plastic state (not melted) and stirred using a stir rod. The FSW pin tool is an integrated geometrical structure consisting of a large-diameter shoulder, and a smaller-diameter stir pin protruding from the shoulder. When the pin is plunged into a weld workpiece, the shoulder spins on the surface of the weld workpiece, thus inducing frictional heat into the part. The pin stirs the fraying surfaces of the weld joint, thus joining the weld workpiece into one structure. The shoulder and stir pin of the FSW pin tool must rotate together at a desired rotational speed. The induced frictional energy control and stir pin control of the pin tool cannot be de-coupled. The two work as one integrated unit. TSW, on the other hand, de-couples the heating and stirring of FSW, and allows for independent control of each process element. A uniquely designed induction coil heats the weld workpiece to a desired temperature, and once heated, the part moves into a stir rod whose RPM is also independently controlled. As the weld workpiece moves into the stir rod, the piece is positioned, or sandwiched, between upper and lower containment plates. The plate squeezes together, thus compressing the upper and lower surfaces of the weld workpiece. This compressive force, also called consolidation force, consolidates the plastic material within the weld nugget material as it is being stirred by the stir rod. The stir rod is positioned through the center of the top containment plate and protrudes midway through the opposite lower containment plate where it is mechanically captured. The upper and lower containment plates are separated by a

  15. Grain misorientation in thixo-billets prepared by melt stirring

    SciTech Connect

    Nafisi, S.; Szpunar, J.; Vali, H.; Ghomashchi, R.

    2009-09-15

    For semi solid metal (SSM) slurries, in addition to the morphology, size, distribution and percentage of the solid phase particles, the microstructure of individual solid particles is another important parameter to be considered. This is particularly an issue when SSM billets are prepared by continuous stirring of the melt to temperatures below liquidus, as in the case of electromagnetic stirring of Al-Si alloys. Microstructural evolution of the electromagnetically stirred Al-Si alloy is investigated by means of optical and electron microscopy. Electron backscatter diffraction (EBSD) analysis of the stirred and unstirred cast billets has shown stirring to generate local misorientation within individual solid particles. This is an indication of growing dendrites undergoing plastic deformation during the course of SSM slurry preparation. The formation of dislocations and their subsequent rearrangement into subgrain boundaries has been shown by EBSD analysis and TEM studies of thin foil specimens respectively.

  16. Effect of stirring and seeding on whey protein fibril formation.

    PubMed

    Bolder, Suzanne G; Sagis, Leonard M C; Venema, Paul; van der Linden, Erik

    2007-07-11

    The effect of stirring and seeding on the formation of fibrils in whey protein isolate (WPI) solutions was studied. More fibrils of a similar length are formed when WPI is stirred during heating at pH 2 and 80 degrees C compared to samples that were heated at rest. Addition of seeds did not show an additional effect compared to samples that were stirred. We propose a model for fibril formation, including an activation, nucleation, growth, and termination step. The activation and nucleation steps are the rate-determining steps. Fibril growth is relatively fast but terminates after prolonged heating. Two processes that possibly induce termination of fibril growth are hydrolysis of nonassembled monomers and inactivation of the growth ends of the fibrils. Stirring may break up immature fibrils, thus producing more active fibrils. Stirring also seems to accelerate the kinetics of fibril formation, resulting in an increase of the number of fibrils formed.

  17. Modeling of Residual Stresses and Property Distributions in Friction Stir Welds of Aluminum Alloy 6061-T6

    SciTech Connect

    Feng, Zhili; David, Stan A; Wang, Xun-Li; Sklad, Philip S

    2007-01-01

    An integrated thermal-metallurgical-mechanical model is used to analyze and provide insights into the formation of the residual stress and the changes in microstructure and property of Al6061-T6 friction stir welds. The simulations were conducted by means of a three-dimensional finite element model that accounts for the phenomena of frictional heating, weld microstructure and strength changes due to dissolution and reprecipitation of the hardening precipitate particles, and the mechanical workpiece/tool contact during the friction stir welding (FSW) process. The model predictions were confirmed by experimental measurement data from previous studies. For the friction stir welds investigated, it was found that the residual stress distribution is strongly dependent on the welding process parameters and the degree of material softening caused by welding. The recovery of material strength from natural aging does not increase the residual stress in the weld. The failure of friction stir weld under tensile load is controlled by the combination of the reduction in strength and the residual stresses in the heat affected zone (HAZ).

  18. Double Resonance Saturation Recovery in 2,6-Lutidine

    NASA Astrophysics Data System (ADS)

    Mizuno, Kiyoshi; Ishiwata, Mitsumasa

    1983-08-01

    The time variation of the longitudinal magnetization of an individual A-proton line in an AB2-proton system in 2,6-lutidine was observed by the saturation-recovery method under continuous irradiation of a second radio-frequency field to certain particular lines of the B protons. The stirring field was so weak that the spin-tickling effect caused no detectable splitting of the observed line. The dependence of the recovery time TH2 on the strength H2 of the stirring field differs according to the combination of the observed and the stirred lines; as H2 increases, the TH2 for regressively connected lines increases monotonically, that for unconnected lines hardly changes, and that for progressively connected lines decreases at first and then increases.

  19. Microbial enhanced oil recovery research

    SciTech Connect

    Sharma, M.M.; Georgiou, G.

    1990-03-01

    In the previous quarterly report we described the criteria for selecting a microorganism for Microbial Enhanced Oil Recovery studies. After careful consideration we chose Bacillus licheniformis JF-2 because of its ability to withstand reservoir conditions and the production of a surface active lipopeptide. Detailed experiments were conducted in stirred tank fermenters equipped with pH control and constant sparging of air or, in the case of anaerobic experiments, O{sub 2}-free nitrogen. The effect of temperature and pH on biomass production, glucose consumption and interfacial tension against decane were determined for both aerobic and anaerobic conditions. 5 figs., 2 tabs.

  20. Metal Flow in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2006-01-01

    The plastic deformation field in Friction Stir Welding (FSW) is compared to that in metal cutting. A shear surface around the FSW tool analogous to the metal cutting shear plane is identified and comprises the basis of the "rotating plug" flow field model and the "wiping" model of tool interaction with weld metal. Within the context of these models: The FSW shear rate is estimated to be comparable to metal cutting shear rates. The effect of tool geometry on the FSW shear surface is discussed and related to published torque measurements. Various FS W structural features are explained, including a difference in structure of bimetallic welds when alloys on the advancing and retreating sides of the weld seam are exchanged. The joining mechanism and critical parameters of the FSW process are made clear.

  1. Ultrasonically-assisted Thermal Stir Welding System

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2014-01-01

    A welding head assembly has a work piece disposed between its containment plates' opposing surfaces with the work piece being maintained in a plastic state thereof at least in a vicinity of the welding head assembly's stir rod as the rod is rotated about its longitudinal axis. The welding head assembly and the work piece experience relative movement there between in a direction perpendicular to the rod's longitudinal axis as the work piece is subjected to a compressive force applied by the containment plates. A first source coupled to the first containment plate applies a first ultrasonic wave thereto such that the first ultrasonic wave propagates parallel to the direction of relative movement. A second source coupled to the second containment plate applies a second ultrasonic wave thereto such that the second ultrasonic wave propagates parallel to the direction of relative movement.propagates parallel to the direction of relative movement.

  2. Laser Peening Effects on Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Hatamleh, Omar

    2011-01-01

    Friction Stir Welding (FSW) is a welding technique that uses frictional heating combined with forging pressure to produce high strength bonds. It is attractive for aerospace applications. Although residual stresses in FSW are generally lower when compared to conventional fusion welds, recent work has shown that significant tensile residual stresses can be present in the weld after fabrication. Therefore, laser shock peening was investigated as a means of moderating the tensile residual stresses produced during welding. This slide presentation reviews the effect of Laser Peening on the weld, in tensile strength, strain, surface roughness, microhardness, surface wear/friction, and fatigue crack growth rates. The study concluded that the laser peening process can result in considerable improvement to crack initiaion, propagation and mechanical properties in FSW.

  3. Tool Forces Developed During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Melendez, M.; Tang, W.; Schmidt, C.; McClure, J. C.; Nunes, A. C.; Murr, L. E.

    2003-01-01

    This paper will describe a technique for measuring the various forces and the torque that exist on the Friction Stir Welding pin tool. Results for various plunge depths, weld speeds, rotational speed, and tool configurations will be presented. Welds made on 6061 aluminum with typical welding conditions require a downward force of 2800 lbs. (12.5 kN) a longitudinal force in the direction of motion of 300 lbs (1.33 kN), a transverse force in the omega x v direction of 30 lbs (135 N). Aluminum 2195 under typical weld conditions requires a downward force of 3100 lbs. (1.38 kN), a longitudinal force of 920 lbs. (4.1 kN), and a transverse force of 45 lbs. (200 N) in the omega x v direction.

  4. In-process discontinuity detection during friction stir welding

    NASA Astrophysics Data System (ADS)

    Shrivastava, Amber

    The objective of this work is to develop a method for detecting the creation of discontinuities (e.g., voids) during friction stir welding. Friction stir welding is inherently cost-effective, however, the need for significant weld inspection can make the process cost-prohibitive. A new approach to weld inspection is required -- where an in-situ characterization of weld quality can be obtained, reducing the need for post-process inspection. Friction stir welds with discontinuity and without discontinuity were created. In this work, discontinuities are generated by reducing the friction stir tool rotation frequency and increasing the tool traverse speed in order to create "colder" welds. During the welds, forces are measured. Discontinuity sizes for welds are measured by computerized tomography. The relationship between the force transients and the discontinuity sizes indicate that the force measurement during friction stir welding can be effectively used for detecting discontinuities in friction stir welds. The normalized force transient data and normalized discontinuity size are correlated to develop a criterion for discontinuity detection. Additional welds are performed to validate the discontinuity detection method. The discontinuity sizes estimated by the force measurement based method are in good agreement with the discontinuity sizes measured by computerized tomography. These results show that the force measurement based discontinuity detection model method can be effectively used to detect discontinuities during friction stir welding.

  5. A fast stir bar sorptive extraction method for the analysis of geosmin and 2-methylisoborneol in source and drinking water.

    PubMed

    Bauld, T; Teasdale, P; Stratton, H; Uwins, H

    2007-01-01

    The presence of unpleasant taste and odour in drinking water is an ongoing aesthetic concern for water providers worldwide. The need for a sensitive and robust method capable of analysis in both natural and treated waters is essential for early detection of taste and odour events. The purpose of this study was to develop and optimise a fast stir bar sorptive extraction (SBSE) method for the analysis of geosmin and 2-methylisoborneol (MIB) in both natural water and drinking water. Limits of detection with the optimised fast method (45 min extraction time at 60 degrees C using 24 microL stir bars) were 1.1 ng/L for geosmin and 4.2 ng/L for MIB. Relative standard deviations at the detection limits were under 17% for both compounds. Use of multiple stir bars can be used to decrease the detection limits further. The use of 25% NaCl and 5% methanol sample modifiers decreased the experimental recoveries. Likewise, addition of 1 mg/L and 1.5 mg/L NaOCI decreased the recoveries and this effect was not reversed by addition of 10% thiosulphate. The optimised method was used to measure geosmin concentrations in treated and untreated drinking water. MIB concentrations were below the detection limits in these waters.

  6. Friction stir processing on high carbon steel U12

    SciTech Connect

    Tarasov, S. Yu. Rubtsov, V. E.; Melnikov, A. G.

    2015-10-27

    Friction stir processing (FSP) of high carbon steel (U12) samples has been carried out using a milling machine and tools made of cemented tungsten carbide. The FSP tool has been made in the shape of 5×5×1.5 mm. The microstructural characterization of obtained stir zone and heat affected zone has been carried out. Microhardness at the level of 700 MPa has been obtained in the stir zone with microstructure consisting of large grains and cementitte network. This high-level of microhardness is explained by bainitic reaction developing from decarburization of austenitic grains during cementite network formation.

  7. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Hovanski, Yuri; Grant, Glenn J.; Santella, M. L.

    2009-11-13

    Friction stir spot welding techniques were developed to successfully join several advanced high strength steels. Two distinct tool materials were evaluated to determine the effect of tool materials on the process parameters and joint properties. Welds were characterized primarily via lap shear, microhardness, and optical microscopy. Friction stir spot welds were compared to the resistance spot welds in similar strength alloys by using the AWS standard for resistance spot welding high strength steels. As further comparison, a primitive cost comparison between the two joining processes was developed, which included an evaluation of the future cost prospects of friction stir spot welding in advanced high strength steels.

  8. Wastewater treatment by radial freezing with stirring effects.

    PubMed

    Gay, Guillaume; Lorain, Olivier; Azouni, Aza; Aurelle, Yves

    2003-05-01

    Radial freezing experiments on wastewater models were conducted in the presence of imposed stirring in order to remove impurities. The studied samples (dilute Na-montmorillonite suspensions charged with nitrates and with zinc or lead) were placed inside a cylindrical annulus, cooled at a controlled temperature around -7 degrees C at its inner wall which rotated around a vertical axis. The freezing front propagated toward the still outer wall which was maintained at a constant temperature around +1 degrees C. Thanks to stirring, considerable purification rates up to 99.97% were attained. It was also demonstrated that combining radial freezing and stirring ended in residual concentrations which agreed with drinking water standards.

  9. Adiabatic inversion pulses for myocardial T1-mapping

    PubMed Central

    Kellman, Peter; Herzka, Daniel A.; Hansen, Michael Schacht

    2013-01-01

    Purpose To evaluate the error in T1-estimates using inversion recovery based T1-mapping due to imperfect inversion, and perform a systematic study of adiabatic inversion pulse designs in order to maximize inversion efficiency for values of transverse relaxation (T2) in the myocardium subject to a peak power constraint. Methods The inversion factor for hyperbolic secant (HS) and tangent/hyperbolic tangent (tan/tanh) adiabatic full passage waveforms was calculated using Bloch equations. A brute force search was conducted of design parameters: pulse duration, frequency range, shape parameters, and peak amplitude. A design was selected that maximized the inversion factor over a specified range of amplitude and off-resonance and validated using phantom measurements. Empirical correction for imperfect inversion was performed. Results The tan/tanh adiabatic pulse was found to outperform HS designs, and achieve an inversion factor of 0.96 within ±150 Hz over 25% amplitude range with 14.7 μTesla peak amplitude. T1-mapping errors of the selected design due to imperfect inversion was approx. 4% and could be corrected to <1%. Conclusion Non-ideal inversion leads to significant errors in inversion recovery based T1-mapping. The inversion efficiency of adiabatic pulses is sensitive to transverse relaxation. The tan/tanh design achieved the best performance subject to the peak amplitude constraint. PMID:23722695

  10. Determination of hormones in milk by hollow fiber-based stirring extraction bar liquid-liquid microextraction gas chromatography mass spectrometry.

    PubMed

    Xu, Xu; Liang, Fanghui; Shi, Jiayuan; Zhao, Xin; Liu, Zhuang; Wu, Lijie; Song, Ying; Zhang, Hanqi; Wang, Ziming

    2013-08-06

    The hollow fiber-based stirring extraction bar liquid-liquid microextraction was applied to the extraction of hormones, including 17-α-ethinylestradiol, 17-α-estradiol, estriol, 17-β-estradiol, estrone, 17-α-hydroxyprogesterone, medroxyprogesterone, progesterone and norethisterone acetate, in milk. The present method has the advantages of both hollow fiber-liquid phase microextraction and stirring bar sorptive extraction. The stirring extraction bar was used as both the stirring bar of microextraction, and extractor of the analytes, which can make extraction, clean-up and concentration be carried out in one step. When the extraction was completed, the stirring extraction bar was easy isolated from the extraction system with the magnet. Several experimental parameters, including the type of extraction solvent, the number of hollow stirring extraction bar, extraction time, stirring speed, ionic strength, and desorption conditions were investigated and optimized. The analytes in the extract were derived and determined by gas chromatography mass spectrometry. Under optimal experimental conditions, good linearity was observed in the range of 0.20-20.00ng mL(-1). The limits of detection and quantification were in the range of 0.02-0.06ng mL(-1) and 0.07-0.19ng mL(-1), respectively. The present method was applied to the analysis of milk samples, and the recoveries of analytes were in the range of 93.6-104.6% with the relative standard deviations ranging from 1.6% to 6.2% (n=5). The results showed that the present method was a rapid and feasible method for the determination of hormones in milk samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. An improved hollow fiber solvent-stir bar microextraction for the preconcentration of anabolic steroids in biological matrix with determination by gas chromatography-mass spectrometry.

    PubMed

    Liu, Wei; Zhang, Lan; Fan, Liangbiao; Lin, Zian; Cai, Yimin; Wei, Zhenyi; Chen, Guonan

    2012-04-13

    In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent "bar" not floating at the sample solution and exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15 μL toluene, 40 °C, stirring at 750 rpm for 30 min with 1.5 g sodium chloride addition in 20.0 mL donor phase), the linear ranges of anabolic steroids were 0.25-200 ng mL(-1) with gas chromatography-mass spectrometry. The limits of detection were lower than 0.10 ng mL(-1). The recoveries and precisions in spiked urine and hair samples were between 73.97-93.56% and 2.18-4.47% (n=5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method.

  12. Characterization of friction stir welded joint of low nickel austenitic stainless steel and modified ferritic stainless steel

    NASA Astrophysics Data System (ADS)

    Mondal, Mounarik; Das, Hrishikesh; Ahn, Eun Yeong; Hong, Sung Tae; Kim, Moon-Jo; Han, Heung Nam; Pal, Tapan Kumar

    2017-09-01

    Friction stir welding (FSW) of dissimilar stainless steels, low nickel austenitic stainless steel and 409M ferritic stainless steel, is experimentally investigated. Process responses during FSW and the microstructures of the resultant dissimilar joints are evaluated. Material flow in the stir zone is investigated in detail by elemental mapping. Elemental mapping of the dissimilar joints clearly indicates that the material flow pattern during FSW depends on the process parameter combination. Dynamic recrystallization and recovery are also observed in the dissimilar joints. Among the two different stainless steels selected in the present study, the ferritic stainless steels shows more severe dynamic recrystallization, resulting in a very fine microstructure, probably due to the higher stacking fault energy.

  13. Understanding the role of molar mass and stirring in polymer dissolution.

    PubMed

    Valois, Pauline; Verneuil, Emilie; Lequeux, Francois; Talini, Laurence

    2016-10-04

    When a dry soluble polymer is put in contact with a large quantity of solvent, it swells and forms a transient gel, and eventually, yields a dilute solution of polymers. Everyday lab experience shows that when the molar mass is large, namely tens of times larger than entanglement mass, this dissolution process is slow and difficult and may require stirring. Here, in agreement with previous results, we found that the time needed to turn a dry grain into a dilute solution is not limited by water diffusion in the glassy or semi-crystalline dry polymer, but rather by the life-time of the transient gel made of entangled chains. In addition, we shed new light on the dissolution process by demonstrating that, in contrast to theoretical predictions, the gel life-time is not governed by reptation. We show instead that swelling is simply controlled by the osmotic pressure and the gel permeability until the overlap concentration is reached within the gel. At this stage, the gel turns into a dilute solution in which polymers are dispersed by natural convection. The observed dependence of the dissolution process on the molar mass therefore originates from the molar mass dependent overlap concentration. Under stirring, or forced convection, the polymer gel disappears at a higher critical concentration that depends on the shear rate. We suggest a description of the experimental data which uses the rheological flow curves of the solutions of the considered polymer. Inversely, dissolution times of polymer powders under stirring can be inferred from classical rheological measurements of the polymer solutions at varied concentrations.

  14. Computational Analysis of Material Flow During Friction Stir Welding of AA5059 Aluminum Alloys

    DTIC Science & Technology

    2011-01-01

    273 7906. J.Q. Su, T.W. Nelson, R. Mishra, and M. Mahoney, Microstructural 791Investigation of Friction Stir Welded 7050 -T651 Aluminum , Acta 792Mater...REPORT Computational Analysis of Material Flow During Friction Stir Welding of AA5059 Aluminum Alloys 14. ABSTRACT 16. SECURITY CLASSIFICATION OF...During Friction Stir Welding of AA5059 Aluminum Alloys Report Title ABSTRACT Workpiece material flow and stirring/mixing during the friction stir welding

  15. Friction Stir Spot Welding of DP780 Carbon Steel

    SciTech Connect

    Santella, M. L.; Hovanski, Yuri; Frederick, Alan; Grant, Glenn J.; Dahl, Michael E.

    2009-09-15

    Friction stir spot welds were made in uncoated and galvannneled DP780 sheets using polycrystalline boron nitride stir tools. The tools were plunged at either a single continuous rate or in two segments consisting of a relatively high rate followed by a slower rate of shorter depth. Welding times ranged from 1-10 s. Increasing tool rotation speed from 800 to 1600 rpm increased strength values. The 2-segment welding procedures also produced higher strength joints. Average lap-shear strengths exceeding 10.3 kN were consistently obtained in 4 s on both the uncoated and the galvannealed DP780. The likelihood of diffusion and mechanical interlocking contributing to bond formation was supported by metallographic examinations. A cost analysis based on spot welding in automobile assembly showed that for friction stir spot welding to be economically competitive with resistance spot welding the cost of stir tools must approach that of resistance spot welding electrode tips.

  16. Evidence of induced chirality in stirred solutions of supramolecular nanofibers.

    PubMed

    Arteaga, Oriol; Canillas, Adolf; Purrello, Roberto; Ribó, Josep M

    2009-07-15

    Two-modulator generalized ellipsometry is used to determine the spectroscopic Mueller matrix of a solution of porphyrin supramolecular aggregates that have fibrous form. During the measurements the solutions were stirred in clockwise and anticlockwise directions. The pseudopolar decompostion is applied to the experimental Mueller matrices to unveil the birefringent and dichroics properties of the sample. The vortex flow in the stirred solution is found to modify the optical response of the aggregates to polarized light, and, in particular, its chiral signature is determined by the stirring direction in a totally reversible process. The data found show that chirality can be induced by stirring in solutions of supramolecular fibers and that a effective transfer of chirality from a macroscopic phenomenon to the supramolecular structures takes place.

  17. 17. DETAIL VIEW OF WHAT APPEARS TO BE STIRRING FORK ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. DETAIL VIEW OF WHAT APPEARS TO BE STIRRING FORK THAT MIXED COFFEE BEANS AS THEY WERE HUSKED - Hacienda Cafetalera Santa Clara, Coffee Mill, KM 19, PR Route 372, Hacienda La Juanita, Yauco Municipio, PR

  18. Condensed-matter physics: History matters for a stirred superfluid

    NASA Astrophysics Data System (ADS)

    Davis, Matthew J.; Helmerson, Kristian

    2014-02-01

    The observation of path dependence in the response of a superfluid to stirring promises potential applications in precision rotation sensing, and provides a test bed for microscopic theories of ultracold atomic gases. See Letter p.200

  19. Vortex annihilation and inverse cascades in two dimensional superfluid turbulence

    NASA Astrophysics Data System (ADS)

    Lucas, Andrew; Chesler, Paul M.

    2015-03-01

    The dynamics of a dilute mixture of vortices and antivortices in a turbulent two-dimensional superfluid at finite temperature is well described by first order Hall-Vinen-Iordanskii equations, or dissipative point vortex dynamics. These equations are governed by a single dimensionless parameter: the ratio of the strength of drag forces to Magnus forces on vortices. When this parameter is small, we demonstrate using numerical simulations that the resulting superfluid enjoys an inverse energy cascade where small scale stirring leads to large scale vortex clustering. We argue analytically and numerically that the vortex annihilation rate in a laminar flow may be parametrically smaller than the rate in a turbulent flow with an inverse cascade. This suggests a new way to detect inverse cascades in experiments on two-dimensional superfluid turbulence using cold atomic gases, where traditional probes of turbulence such as the energy spectrum are not currently accessible.

  20. Friction Stir Welding of Aluminum and Titanium Alloys

    DTIC Science & Technology

    2007-11-02

    What is this? Jata/US Air Force Typical FSW Tools W-Re tool in collet- style tool holder. Used for welding steels and Ti alloys 3-piece self...Friction Stir Welding of Aluminum and Titanium alloys NATO Advanced Research Workshop Metallic Materials with High Structural Efficiency Kyiv...valid OMB control number. 1. REPORT DATE 18 MAR 2004 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Friction Stir Welding of Aluminum

  1. STIR: Microwave Response of Carbon Nanotubes in Polymer Nanocomposite Welds

    DTIC Science & Technology

    2016-01-28

    STIR: RDRL-ROE-M: Microwave Response of Carbon Nanotubes in Polymer Nanocomposite Welds Thrust 1 of the STIR project examines the heat response of...polymer composites loaded with carbon nanotubes (CNTs) to microwave irradiation. This involves (1) a study of how CNT loading affects dielectric...27709-2211 polymer, carbon nanotube , manufacturing, diffusion, heating, microwave REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S

  2. Thermo-Mechanical Processing in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Schneider, J. A.; Nunes, A. C., Jr.

    2002-01-01

    In Friction Stir Welding (FSW) a rotating pin-tool inserted into a weld seam literally stirs the edges of the seam together. In this study, two flow paths are proposed that define the FWS zone. Studies using a longitudinal tungsten wire (0.0025 dia.) were used to visualize and document the material flow. The material flow path is described using a mathematical model.

  3. Friction Stir Processing for Efficient Manufacturing

    SciTech Connect

    Mr. Christopher B. Smith; Dr. Oyelayo Ajayi

    2012-01-31

    Friction at contacting surfaces in relative motion is a major source of parasitic energy loss in machine systems and manufacturing processes. Consequently, friction reduction usually translates to efficiency gain and reduction in energy consumption. Furthermore, friction at surfaces eventually leads to wear and failure of the components thereby compromising reliability and durability. In order to reduce friction and wear in tribological components, material surfaces are often hardened by a variety of methods, including conventional heat treatment, laser surface hardening, and thin-film coatings. While these surface treatments are effective when used in conjunction with lubrication to prevent failure, they are all energy intensive and could potentially add significant cost. A new concept for surface hardening of metallic materials and components is Friction Stir Processing (FSP). Compared to the current surface hardening technologies, FSP is more energy efficient has no emission or waste by products and may result in better tribological performance. FSP involves plunging a rotating tool to a predetermined depth (case layer thickness) and translating the FSP tool along the area to be processed. This action of the tool produces heating and severe plastic deformation of the processed area. For steel the temperature is high enough to cause phase transformation, ultimately forming hard martensitic phase. Indeed, FSP has been used for surface modification of several metals and alloys so as to homogenize the microstructure and refine the grain size, both of which led to improved fatigue and corrosion resistance. Based on the effect of FSP on near-surface layer material, it was expected to have beneficial effects on friction and wear performance of metallic materials. However, little or no knowledge existed on the impact of FSP concerning friction and wear performance the subject of the this project and final report. Specifically for steel, which is the most dominant

  4. Friction Stir Welding of Curved Plates

    NASA Technical Reports Server (NTRS)

    Sanchez, Nestor

    1999-01-01

    Friction stir welding (FSW) is a remarkable technology for making butt and lap joints in aluminum alloys. The process operates by passing a rotating tool between two closely butted plates. This process generates heat and the heated material is stirred from both sides of the plates to generate a high quality weld. Application of this technique has a very broad field for NASA. In particular, NASA is interested in using this welding process to manufacture tanks and curved elements. Therefore, this research has been oriented to the study the FSW of curved plates. The study has covered a number of topics that are important in the model development and to uncover the physical process involve in the welding itself. The materials used for the experimental welds were as close to each other as we could possibly find, aluminum 5454-0 and 5456-0 with properties listed at http://matweb.com. The application of FSW to curved plates needs to consider the behavior that we observed in this study. There is going to be larger force in the normal direction (Fz) as the curvature of the plate increases. A particular model needs to be derived for each material and thickness. A more complete study should also include parameters such as spin rate, tool velocity, and power used. The force in the direction of motion (Fx) needs to be reconsidered to make sure of its variability with respect to other parameters such as velocity, thickness, etc. It seems like the curvature does not play a role in this case. Variations in temperature were found with respect to the curvature. However, these changes seem to be smaller than the effect on Fz. The temperatures were all below the melting point. We understand now that the process of FSW produces a three dimensional flow of material that takes place during the weld. This flow needs to be study in a more detailed way to see in which directions the flow of material is stronger. It could be possible to model the flow using a 2-dimensional model in the

  5. Flow Trajectories in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Bernstein, Edward L.

    1999-01-01

    In the Friction Stir Welding (FSW) process, a rotating, shouldered tool with a threaded pin is inserted under pressure along the seam of two pieces of metal which are tightly clamped together, and secured against a rigid anvil underneath. The rotating pin travels along the seam and through a combination of pressure and friction heating produces a zone of plastic deformation around the pin within the workpiece on either side of the seam. As the pin is moved in the direction of welding, the plasticised material moves around the tool and bonds together behind it. The elements of the material flow behavior are a combination of three elements. There is a rotational transport of material being carried around the tool, extrusion of material being forced around the pin on both sides into the cavity created behind it, and a lifting and dropping of material as it is stirred and mixed by the rotating action of the pin. It was assumed that rotational motion of the plastic zone is the primary mechanism for transport of material around the welding tool. A kinematic mathematical model was used to compute trajectories of material movement for various distributions of rotational slip within the plastic zone. These trajectories were then compared with the results of an experiment that produced radiographs of markers embedded in a workpiece that was welded with the FSW process. It was assumed that the copper wire markers retained their original length as the aluminum material flowed around them. The kinematic model included a constraint so that the displacements were such that the total length of the wire markers did not increase after deformation. There was good agreement between the calculated trajectories for the case of localized slip at the outer surface of the plastic deformation zone and the radiographs of the copper wire markers. The trajectories differed markedly from the radiograph traces when a distributed slip zone was assumed. It was concluded that the flow field could

  6. Mechanism for Self-Reacted Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Venable, Richard; Bucher, Joseph

    2004-01-01

    A mechanism has been designed to apply the loads (the stirring and the resection forces and torques) in self-reacted friction stir welding. This mechanism differs somewhat from mechanisms used in conventional friction stir welding, as described below. The tooling needed to apply the large reaction loads in conventional friction stir welding can be complex. Self-reacted friction stir welding has become popular in the solid-state welding community as a means of reducing the complexity of tooling and to reduce costs. The main problems inherent in self-reacted friction stir welding originate in the high stresses encountered by the pin-and-shoulder assembly that produces the weld. The design of the present mechanism solves the problems. The mechanism includes a redesigned pin-and-shoulder assembly. The welding torque is transmitted into the welding pin by a square pin that fits into a square bushing with set-screws. The opposite or back shoulder is held in place by a Woodruff key and high-strength nut on a threaded shaft. The Woodruff key reacts the torque, while the nut reacts the tensile load on the shaft.

  7. Effect of stirring on the safety of flammable liquid mixtures.

    PubMed

    Liaw, Horng-Jang; Gerbaud, Vincent; Chen, Chan-Cheng; Shu, Chi-Min

    2010-05-15

    Flash point is the most important variable employed to characterize fire and explosion hazard of liquids. The models developed for predicting the flash point of partially miscible mixtures in the literature to date are all based on the assumption of liquid-liquid equilibrium. In real-world environments, however, the liquid-liquid equilibrium assumption does not always hold, such as the collection or accumulation of waste solvents without stirring, where complete stirring for a period of time is usually used to ensure the liquid phases being in equilibrium. This study investigated the effect of stirring on the flash-point behavior of binary partially miscible mixtures. Two series of partially miscible binary mixtures were employed to elucidate the effect of stirring. The first series was aqueous-organic mixtures, including water+1-butanol, water+2-butanol, water+isobutanol, water+1-pentanol, and water+octane; the second series was the mixtures of two flammable solvents, which included methanol+decane, methanol+2,2,4-trimethylpentane, and methanol+octane. Results reveal that for binary aqueous-organic solutions the flash-point values of unstirred mixtures were located between those of the completely stirred mixtures and those of the flammable component. Therefore, risk assessment could be done based on the flammable component flash-point value. However, for the assurance of safety, it is suggested to completely stir those mixtures before handling to reduce the risk. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  8. Magnetic properties of friction stir processed composite

    SciTech Connect

    Das, Shamiparna; Martinez, Nelson Y.; Das, Santanu; Mishra, Rajiv S.; Grant, Glenn J.; Jana, Saumyadeep; Polikarpov, Evgueni

    2016-03-29

    There are many existing inspection systems each with their own advantages and drawbacks. These usually comprise of semi-remote sensors which frequently causes difficulty in reaching complex areas of a component. This study proposes to overcome that difficulty by developing embedded functional composites. Through this route, embedding can be achieved in virtually any component part and can be periodically interrogated by a reading device. The “reinforcement rich” processed areas can then be utilized to record properties like strain, temperature, stress state etc. depending on the reinforcement material. In this work, friction stir processing (FSP) was utilized to fabricate a magnetostrictive composite by embedding galfenol particles into a nonmagnetic aluminum (Al) matrix. It targets to develop a composite that produces strain in a varying magnetic field. Reinforcements were observed to be distributed uniformly in the matrix. Magnetization curves were studied using a vibrating sample magnetometer (VSM). A simple and cheap setup was developed to measure the magnetostrictive strain of the composites. Important factors affecting the magnetic properties were identified and ways to improve the magnetic properties discussed.

  9. Material Flow During Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Guerra, M.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported in two distinct streams or currents. One stream is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug. After one or more rotations, this material is sloughed off the plug in the wake of the tool primarily on the advancing side. The second stream of material is an entrainment of material from the retreating side of the nib that fills in between the sloughed off pieces from the advancing side. These two processes produce material with different mechanical properties and the strength of a weld should depend on the relative importance of the processes.

  10. The Plunge Phase of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    McClure, John C.

    2005-01-01

    The many advantages of Friction Stir Welding have led to a relatively rapid acceptance in the often conservative welding community. Because the process is so different from traditional fusion welding, with which most investigators are most familiar, there remain many aspects of FSW for which there is no clear consensus. For example, the well known onion rings seen in transverse sections have been variously interpreted as grain size variations, variation in density of second phase particles and parts of the carousel of material rotating with the pin that have been shed from the carousel. Using Orientation Imaging Microscopy, Schneider has recently noted that the onion rings have a different orientation (and hence etch differently) than the surrounding material, and this orientation is consistent with slip plane orientations at the edge of the carousel. Likewise, the forces and torque exerted by the FSW tool on the work piece largely remain unaccounted for. Although these forces are routinely measured by investigators with commercial instrumented welders, they are rarely reported or even qualitatively analyzed. This paper will introduce a model based on a carousel or disk of material that rotates with the tool to estimate the torque and plunge force required to plunge a tool into the work piece. A stationary tool is modeled rather than the moving tool because effects such as thermal transients and metallurgical changes in the sample (primarily aging in aluminum) can be more easily accounted for. It is believed, however, that with some modifications the model should be applicable to a moving tool also.

  11. Metal Flow During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Guerra, M.; Schmidt, C.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes. The first is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug. After one or more rotations, this material is sloughed off the plug in its wake, primarily on the advancing side. The second process is an entrainment of material from the front retreating side of the nib that fills in between the sloughed off pieces from the advancing side. These two processes produce material with different mechanical properties and the strength of a weld should depend on the relative importance of the processes.

  12. Inspecting Friction Stir Welding using Electromagnetic Probes

    NASA Technical Reports Server (NTRS)

    Kinchen, David G.

    2004-01-01

    A report describes the use of advanced electromagnetic probes to measure the dimensions, the spatial distribution of electrical conductivity, and related other properties of friction stir welds (FSWs) between parts made of the same or different aluminum alloy(s). The probes are of the type described in in another Tech Brief. To recapitulate: A probe of this type is essentially an eddy-current probe that includes a primary (driver) winding that meanders and multiple secondary (sensing) windings that meander along the primary winding. Electrical conductivity is commonly used as a measure of heat treatment and tempering of aluminum alloys, but prior to the development of these probes, the inadequate sensitivity and limited accuracy of electrical-conductivity probes precluded such use on FSWs between different aluminum alloys, and the resolution of those probes was inadequate for measurement of FSW dimensions with positions and metallurgical properties. In contrast, the present probes afford adequate accuracy and spatial resolution for the purposes of measuring the dimensions of FSW welds and correlating spatially varying electrical conductivities with metallurgical properties, including surface defects.

  13. Material Flow During Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Guerra, M.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported in two distinct streams or currents. One stream is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug. After one or more rotations, this material is sloughed off the plug in the wake of the tool primarily on the advancing side. The second stream of material is an entrainment of material from the retreating side of the nib that fills in between the sloughed off pieces from the advancing side. These two processes produce material with different mechanical properties and the strength of a weld should depend on the relative importance of the processes.

  14. Nondestructive Ultrasonic Inspection of Friction Stir Welds

    NASA Astrophysics Data System (ADS)

    Tabatabaeipour, M.; Hettler, J.; Delrue, S.; Van Den Abeele, K.

    Friction Stir Welding (FSW) is a relatively new solid-state welding procedure developed at The Welding Institute (TWI-UK) and the technique is widely employed for welding aluminum alloys in various applications. In order to examine the quality of the welds and to detect a variety of welding flaws such as wormholes and root-flaws, it is required to develop a methodical inspection technique that can be used for the identification and localization of such defects. The most prevalent and risky defect in this type of welding is the barely visible root flaw with a length varying from 100-700 μm. Due to the extreme characteristics of the flaw, off-the-shelf ultrasonic weld inspection methods are not always able to readily detect this type of minute defect feature. Here, we propose a novel approach to characterize root flaws using an oblique incident ultrasonic C-scan backscattering analysis. The implementation consists of an immersion ultrasonic testing method in pulse echo (i.e. backscatter) mode with a 3.5 MHz transducer, and makes use of an empirical procedure to engender of a shear wave dominated excitation at the root surface, and to properly gate the received signal for root flaw examination. By scanning the surface above the welded component, a C-scan image displaying the backscatter response from the root surface of the nugget zone can be obtained which allows a simple interpretation of the root flaw status of the weld.

  15. Langangian Particle Model of Friction Stir Welding

    SciTech Connect

    Tartakovsky, Alexandre M.

    2006-12-13

    Since its invention fifteen years ago, Friction Stir Welding (FSW) has found commercial application in the marine, aerospace, rail, and now automotive industries. Development of the FSW process for each new application, however, has remained largely empirical. Few detailed numerical modeling techniques have been developed that can explain and predict important features of the process physics. This is particularly true in the areas of material flow, mixing mechanisms, and void prediction. In this paper we present a novel modeling approach to simulate FSW processes that may have significant advantages over current traditional finite element or finite difference based methods. The proposed model is based on the Smoothed Particle Hydrodynamics (SPH) method. Unlike traditional grid-based methods, Lagrangian particle methods such as SPH can simulate the dynamics of interfaces, large material deformations, void formations and the material's strain and temperature history without employing complex tracking schemes. Two- and three-dimensional FSW simulations for different tool designs are presented. Preliminary numerical results are in qualitative agreement with experimental observations. Detailed comparisons between experimental measurements and larger scale FSW simulations are required to further validate and calibrate the SPH based FSW model.

  16. Covalent immobilization of graphene onto stainless steel wire for jacket-free stir bar sorptive extraction.

    PubMed

    Zhang, Wenpeng; Zhang, Zixin; Zhang, Juan; Meng, Jiawei; Bao, Tao; Chen, Zilin

    2014-05-23

    Stainless steel wire is a good substrate for jacket-free stir bar sorptive extraction (SBSE). In this work, we present the first example of chemical modification of graphene on stainless steel wire (SSW) for SBSE. Bio-inspired polydopamine was firstly modified on the SSW covalently; then graphene oxide was introduced and reacted with amino groups of polydopamine layer. The modification of polydopamine and graphene can be repeated by a layer-by-layer strategy, resulting in control of the thickness of graphene layer and increase of extraction capability. The prepared covalently immobilized graphene-stainless steel wire (G-SSW) exhibited good stability under stirring, ultrasonication and treatment with commonly used organic solvents, basic and acidic solutions. Application as stir bar for SBSE, G-SSW was found to possess good extraction efficiency towards pollutant polyaromatic hydrocarbons (PAHs), with enrichment factors from 10086 to 16896. After optimization of conditions, G-SSW based SBSE was coupled HPLC for determination of PAHs in environmental and food samples. The quantitative method has low limits of detection of 0.2-50pg/mL, which is better than some reported SBSE-HPLC methods. The method shows wide linear range (200-5000, 10-1000 and 1-1000pg/mL), good linearity (r≥0.9950) and good reproducibility (RSD≤4.97%). The method has been applied to soil and food samples, with good selectivity and good recoveries ranging from 88.5-113.6%. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Locative Inversion in Cantonese.

    ERIC Educational Resources Information Center

    Mok, Sui-Sang

    This study investigates the phenomenon of "Locative Inversion" in Cantonese. The term "Locative Inversion" indicates that the locative phrase (LP) syntactic process in Cantonese and the appears at the sentence-initial position and its logical subject occurs postverbally. It is demonstrated that this Locative Inversion is a…

  18. Stirring bar sorptive extraction in the determination of PAHs in drinking waters.

    PubMed

    García-Falcón, M S; Cancho-Grande, B; Simal-Gándara, J

    2004-04-01

    The application of a new extraction technique which is known as stir bar sorptive extraction (SBSE), followed by high-performance liquid chromatography with a fluorescence detector, was assessed for determining eight polycyclic aromatic hydrocarbons (PAHs) in water samples. The extraction conditions such as acetonitrile addition; effects of temperature and salt; and finally, extraction and desorption time profiles were studied. Once SBSE was optimized, analytical method parameters such as linearity (r(2)>0.991), precision (<9%), detection (0.5-7.3 ng/L) and quantitation (1.0-22 ng/L) limits were estimated. To correct for the 43-57% absolute recovery depending on the PAH, calibration was done with a line obtained submitting standard-spiked blank tap waters to the complete sample treatment and analysis. Consequently, relative recovery was about 100% because all water samples (those for calibration purposes and those for recovery estimation) were processed in the same way and the absolute recovery remained constant. SBSE method characteristics were checked with the analysis of real drinking waters in the search for PAHs.

  19. Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy.

    PubMed

    Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo

    2013-12-18

    Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

  20. Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy

    PubMed Central

    Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo

    2013-01-01

    Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force. PMID:28788430

  1. System for Controlling the Stirring Pin of a Friction Stir Welding Apparatus

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor); Romine, Peter L. (Inventor); Oelgoetz, Peter A. (Inventor)

    2002-01-01

    A control is provided for a friction stir welding apparatus comprising a pin tool which includes a shoulder and a rotating pin extending outwardly from the shoulder of the pin tool and which, in use, is plunged into a workpiece formed contacting workpiece members to stir weld the members together. The control system controls the penetration of the pin tool into the workpiece members which are mounted on a support anvil. The control system includes a pin length controller for controlling pin length relative to the shoulder and for producing a corresponding pin length signal. A pin force sensor senses the force being exerted on the pin during welding and produces a corresponding actual pin force signal. A probe controller controls a probe extending outwardly from the pin, senses a parameter related to the distance between the probe and the supporting anvil and produces a corresponding probe signal. A workpiece standoff sensor senses the standoff distance between the workpiece and the standoff sensor and produces a corresponding standoff signal. A control unit receives the various signals, together with a weld schedule, and, based on these signals and the weld schedule, controls the pin length controller so as to control pin penetration into the workpiece.

  2. Thermal Stir Welding Development at Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Ding, Robert J.

    2008-01-01

    Solid state welding processes have become the focus of welding process development at NASA's Marshall Space Flight Center. Unlike fusion weld processes such as tungsten inert gas (TIG), variable polarity plasma arc (VPPA), electron beam (EB), etc., solid state welding processes do not melt the material during welding. The resultant microstructure can be characterized as a dynamically recrystallized morphology much different than the casted, dentritic structure typical of fusion weld processes. The primary benefits of solid state processes over fusion weld processes include superior mechanic properties and the elimination of thermal distortion and residual stresses. These solid state processes attributes have profoundly influenced the direction of advanced welding research and development within the NASA agency. Thermal Stir Welding (TSW) is a new solid state welding process being developed at the Marshall Space Flight Center. Unlike friction stir welding, the heating, stirring and forging elements of the weld process can be decoupled for independent control. An induction coil induces energy into a workpiece to attain a desired plastic temperature. An independently controlled stir rod, captured within non-rotating containment plates, then stirs the plasticized material followed by forging plates/rollers that work the stirred weld joint. The independent control (decoupling) of heating, stirring and forging allows, theoretically, for the precision control of microstructure morphology. The TSW process is being used to evaluate the solid state joining of Haynes 230 for ARES J-2X applications. It is also being developed for 500-in (12.5 mm) thick commercially pure grade 2 titanium for navy applications. Other interests include Inconel 718 and stainless steel. This presentation will provide metallurgical and mechanical property data for these high melting temperature alloys.

  3. Thermal Stir Welding Development at Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Ding, Robert J.

    2008-01-01

    Solid state welding processes have become the focus of welding process development at NASA's Marshall Space Flight Center. Unlike fusion weld processes such as tungsten inert gas (TIG), variable polarity plasma arc (VPPA), electron beam (EB), etc., solid state welding processes do not melt the material during welding. The resultant microstructure can be characterized as a dynamically recrystallized morphology much different than the casted, dentritic structure typical of fusion weld processes. The primary benefits of solid state processes over fusion weld processes include superior mechanic properties and the elimination of thermal distortion and residual stresses. These solid state processes attributes have profoundly influenced the direction of advanced welding research and development within the NASA agency. Thermal Stir Welding (TSW) is a new solid state welding process being developed at the Marshall Space Flight Center. Unlike friction stir welding, the heating, stirring and forging elements of the weld process can be decoupled for independent control. An induction coil induces energy into a workpiece to attain a desired plastic temperature. An independently controlled stir rod, captured within non-rotating containment plates, then stirs the plasticized material followed by forging plates/rollers that work the stirred weld joint. The independent control (decoupling) of heating, stirring and forging allows, theoretically, for the precision control of microstructure morphology. The TSW process is being used to evaluate the solid state joining of Haynes 230 for ARES J-2X applications. It is also being developed for 500-in (12.5 mm) thick commercially pure grade 2 titanium for navy applications. Other interests include Inconel 718 and stainless steel. This presentation will provide metallurgical and mechanical property data for these high melting temperature alloys.

  4. Friction stir spot welded joints of 409L stainless steels fabricated by a convex shoulder tool

    NASA Astrophysics Data System (ADS)

    Hossain, Md. Abu Mowazzem; Hasan, Md. Tariqul; Hong, Sung-Tae; Miles, Michael; Cho, Hoon-Hwe; Han, Heung Nam

    2013-11-01

    Spot joints of ferritic 409L stainless steel are successfully fabricated by friction stir spot welding (FSSW) using a convex shoulder tool. The welding process, microstructure and failure of the FSSW joint are investigated experimentally. During the FSSW process, the Z-force history shows significant variations depending on the contact phenomena between the tool and the joined sheets, while the Z-torque history shows a rather steady increase without pronounced changes in the trend until the initiation of dwelling. Electron back-scatter diffraction suggests that both continuous dynamic recrystallization and recovery occurred in the stir zone during the FSSW process. Observation of the FSSW joint that failed under the given lap shear load shows that the cracks, which are the result of the interfaces between the upper and lower sheets, propagated into the weld along the interfacial surfaces, after which a necking/shear failure occurred. Finally, the rupture of the joint, which was initiated by the necking/shear failure, propagated along the circumference of the weld.

  5. Stir bar sorptive extraction for the analysis of short-chain chlorinated paraffins in water.

    PubMed

    Llorca-Porcel, Julio; Martínez-Soriano, Esther; Valor, Ignacio

    2009-05-01

    An optimised method using stir bar sorptive extraction (SBSE) and a thermal desorption-GC-electron capture detector (GC-ECD) for the determination of short-chain chlorinated paraffins from water samples was developed. Recoveries near to 100% were obtained by using 20 mm x 0.5 mm (length x film thickness) PDMS commercial stir bars from 200 mL spiked water samples and 20% methanol addition with an extraction period of 24 h. Method sensitivity, linearity and precision were evaluated for surface water and wastewater spiked samples. A LOD of 0.03 and 0.04 microg/L was calculated for surface and wastewater, respectively. The precision of the method given as an RSD was below 20% for both matrices. The developed method was applied for the analysis of two real samples from a contaminated river and a wastewater treatment plant. Results were in accordance with those obtained using a previously developed method based on solid phase microextraction (SPME).

  6. Reading Recovery.

    ERIC Educational Resources Information Center

    Jones, Joanna R., Ed.

    1992-01-01

    This issue of the Arizona Reading Journal focuses on the theme "reading recovery" and includes the following articles: "Why Is an Inservice Programme for Reading Recovery Teachers Necessary?" (Marie M. Clay); "What Is Reading Recovery?" (Gay Su Pinnell); "Teaching a Hard To Teach Child" (Constance A.…

  7. Reading Recovery.

    ERIC Educational Resources Information Center

    Jones, Joanna R., Ed.

    1992-01-01

    This issue of the Arizona Reading Journal focuses on the theme "reading recovery" and includes the following articles: "Why Is an Inservice Programme for Reading Recovery Teachers Necessary?" (Marie M. Clay); "What Is Reading Recovery?" (Gay Su Pinnell); "Teaching a Hard To Teach Child" (Constance A.…

  8. Hollow fiber-stir bar sorptive extraction and microwave assisted derivatization of amino acids in biological matrices.

    PubMed

    Li, Jia; Qi, Huan-Yang; Wang, Yan-Bin; Su, Qiong; Wu, Shang; Wu, Lan

    2016-11-25

    A kind of solid phase microextraction configuration combining the principles of hollow fiber solid phase microextraction (HF-SPME) and stir bar sorptive extraction (SBSE) is presented. The main feature of HF-SBSE is the use of microporous hollow fiber acting as the carrier and filter, while a thin stainless steel wire and silica microspheres in the lumen of hollow fiber respectively acting as the magnetic stirrer and the dispersed sorbents for the collection and extraction of the target analytes, thus affording extraction process like SBSE. Moreover, the prepared hollow fiber stir bar was applied to direct microextraction and microwave assisted derivatization with N,O-Bis(trimethylsilyl)trifluroacetamide (BSTFA) of four amino acids in rats' urine and cerebrospinal fluid followed by gas chromatography mass spectrometric analysis. The limits of detection for four amino acids were found to be in the range of 0.0003-0.017μgmL(-1), and all the analytes did not exhibit any lack of fit. The extraction recoveries using HF-SBSE techniques ranged from 71.8% to 102.3%. The results indicated that hollow fiber stir bar sorptive extraction was a promising technique for the enrichment and direct derivatization of analytes extracted from biological matrices without sample clean-up.

  9. Application of a stir bar sorptive extraction method for the determination of volatile compounds in different grape varieties.

    PubMed

    Vasile-Simone, Giuseppe; Castro, Remedios; Natera, Ramón; Masino, Francesca; Barroso, Carmelo G; Durán-Guerrero, Enrique

    2017-02-01

    Stir bar sorptive extraction (SBSE) has been employed for the analysis of aroma compounds directly from Spanish and Italian grape extracts. The extraction conditions have been optimized using a statistical approach, obtaining results that improve the current state of the art. The proposed analytical conditions were: sample volume 40 mL, extraction time 80 min, 25% (w/v) NaCl and stirring speed 750 rpm using 20 mm × 0.5 mm stir bars. Performance characteristics of the SBSE procedure were further studied and showed correlation coefficients, detection and quantification limits, linear ranges, recoveries and precision values adequate for analysing these compounds in grapes. Twenty-four grape varieties (aromatic and non-aromatic) were analysed. Statistically significant differences (P < 0.05) according to geographical origin were found, being derived mainly from the terpenoid content. By principal component analysis it was possible to note that the terpenoids were more effective in the separation of the non-aromatic samples, showing negative and positive scores for Italian and Spanish grapes, respectively. For non-aromatic grape varieties, the factor 'geographic location' was the most significant, thus corroborating the high influence of this parameter on the volatile composition of grapes and therefore on the genuineness of wines. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  10. A "voice inversion effect?".

    PubMed

    Bédard, Catherine; Belin, Pascal

    2004-07-01

    Voice is the carrier of speech but is also an "auditory face" rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a "voice inversion effect," by analogy to the classical "face inversion effect," which could support the hypothesis of a voice-specific module. Experiment 1 consisted of a gender identification task on two syllables pronounced by 90 speakers (boys, girls, men, and women). Experiment 2 consisted of a speaker discrimination task on pairs of syllables (8 men and 8 women). Experiment 3 consisted of an instrument discrimination task on pairs of melodies (8 string and 8 wind instruments). In all three experiments, stimuli were presented in 4 conditions: (1) no inversion; (2) temporal inversion (e.g., backwards speech); (3) frequency inversion centered around 4000 Hz; and (4) around 2500 Hz. Results indicated a significant decrease in performance caused by sound inversion, with a much stronger effect for frequency than for temporal inversion. Interestingly, although frequency inversion markedly affected timbre for both voices and instruments, subjects' performance was still above chance. However, performance at instrument discrimination was much higher than for voices, preventing comparison of inversion effects for voices vs. non-vocal stimuli. Additional experiments will be necessary to conclude on the existence of a possible "voice inversion effect."

  11. Friction Stir Processing of Particle Reinforced Composite Materials

    PubMed Central

    Gan, Yong X.; Solomon, Daniel; Reinbolt, Michael

    2010-01-01

    The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned.

  12. Microstructural Evolution During Friction Stir Welding of Mild Steel and Ni-Based Alloy 625

    NASA Astrophysics Data System (ADS)

    Fernandez, Johnnatan Rodriguez; Ramirez, Antonio J.

    2017-01-01

    Microstructure evolution during friction stir welding (FSW) of mild steel and Ni-based alloy 625 was studied. Regarding the Ni-based alloy, the welding process led to grain refinement caused by discontinuous and continuous dynamic recrystallization, where bulging of the pre-existing grains and subgrain rotation were the primary mechanisms of recrystallization. In the steel, discontinuous dynamic recrystallization was identified as the recovery process experienced by the austenite. Simple shear textures were observed in the regions affected by the deformation of both materials. Although the allotropic transformation obscured the deformation history, the thermo-mechanically affected zone was identified in the steel by simple shear texture components. A new methodology for the study of texture evolution based on rotations of the slip systems using pole figures is presented as an approximation to describe the texture evolution in FSW.

  13. Determination of free medium-chain fatty acids in beer by stir bar sorptive extraction.

    PubMed

    Horák, Tomás; Culík, Jirí; Jurková, Marie; Cejka, Pavel; Kellner, Vladimír

    2008-07-04

    Free medium-chain fatty acids in beer originate from raw materials, mainly from the fermentation activity of yeasts, and can influence beer taste, vitality of yeasts and also the foam stability of beer. This study presents the development of the method for the determination of free fatty medium-chain acids including caproic acid, caprylic acid, capric acid and lauric acid in beer or wort using stir bar sorptive extraction (SBSE). The combination of this extraction technique with solvent back extraction of the extracted analytes and subsequent gas chromatographic analysis with flame ionization detection was used for the determination of these compounds. The influences of different solvent back solutions, sampling time, solvent back extraction times and different contents of ethanol were studied. The method had high repeatability (RSD <6.7%), good linearity (the correlation coefficients were higher than 0.9963 for quadratic curves over the concentration range 0.5-8.0mg/l) and recoveries 57-89%.

  14. Microstructural Evolution During Friction Stir Welding of Mild Steel and Ni-Based Alloy 625

    NASA Astrophysics Data System (ADS)

    Fernandez, Johnnatan Rodriguez; Ramirez, Antonio J.

    2017-03-01

    Microstructure evolution during friction stir welding (FSW) of mild steel and Ni-based alloy 625 was studied. Regarding the Ni-based alloy, the welding process led to grain refinement caused by discontinuous and continuous dynamic recrystallization, where bulging of the pre-existing grains and subgrain rotation were the primary mechanisms of recrystallization. In the steel, discontinuous dynamic recrystallization was identified as the recovery process experienced by the austenite. Simple shear textures were observed in the regions affected by the deformation of both materials. Although the allotropic transformation obscured the deformation history, the thermo-mechanically affected zone was identified in the steel by simple shear texture components. A new methodology for the study of texture evolution based on rotations of the slip systems using pole figures is presented as an approximation to describe the texture evolution in FSW.

  15. Magnetic metal-organic frameworks coated stir bar sorptive extraction coupled with GC-MS for determination of polychlorinated biphenyls in fish samples.

    PubMed

    Lin, Saichai; Gan, Ning; Qiao, Li; Zhang, Jiabin; Cao, Yuting; Chen, Yinji

    2015-11-01

    In this work, several kinds of the metal-organic framework (MOF) were evaluated the adsorption performance to PCB. Finally, MOF-5(Fe) was introduced in stir bar sorptive extraction (SBSE) as the adsorbent to extract six polychlorinated biphenyls (PCBs). Nd-Fe-B permanent magnet was employed as stir bar, which was then coated with Fe3O4-MOF-5(Fe) composite magnetic material, which was prepared by solvothermal method. The stir bar was then employed to extract and enrich six indicator PCBs (2,2',5,5'-tetrachlorobiphenyl, 2,2',4,5,5'-pentachlorobiphenyl, 2,2',3,4,4',5-hexachlorobiphenyl, 2,3,4,4,5-pentachlorobiphenyl, 2,2',4,4',5,5'-hexachlorobiphenyl, 2,2',3,4,4',5,5'-heptachlorobiphenyl) under stirring, then eluted by n-hexane under ultrasound. Its saturated adsorption amount was found to be 17.0-17.8 mg g(-1) and only 30 min were needed to reach adsorption equilibrium. The MOF-stir bar can be reused for 60 times with the recovery above 80%, which exhibited good stability. Under the optimal experimental conditions, MOF-5(Fe) based SBSE was coupled with GC-MS for detecting six PCBs. The limits of detection (S/N=3) of the developed method were 0.061-0.096 ng g(-1), with enrichment factors of 50-100 fold. And the linear ranges were 0.01-500 μg L(-1). The new method was successfully applied to assess PCBs in fish samples with satisfactory recovery ranging from 94.3% to 97.5%. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. INVERSE STABLE SUBORDINATORS

    PubMed Central

    MEERSCHAERT, MARK M.; STRAKA, PETER

    2013-01-01

    The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled. PMID:25045216

  17. Weld Nugget Temperature Control in Thermal Stir Welding

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2014-01-01

    A control system for a thermal stir welding system is provided. The control system includes a sensor and a controller. The sensor is coupled to the welding system's containment plate assembly and generates signals indicative of temperature of a region adjacent and parallel to the welding system's stir rod. The controller is coupled to the sensor and generates at least one control signal using the sensor signals indicative of temperature. The controller is also coupled to the welding system such that at least one of rotational speed of the stir rod, heat supplied by the welding system's induction heater, and feed speed of the welding system's weld material feeder are controlled based on the control signal(s).

  18. Stirring system for radioactive waste water storage tank

    SciTech Connect

    Ogata, Yoshimune; Nishizawa, Kunihide . Radioisotope Research Center)

    1999-07-01

    A stirring system for 100-m[sup 3] radioactive liquid waste tanks was constructed to unify radioactive concentrations in the tank. The stirring system is effective in certifying that the radioactive concentrations in the tanks are less than the legal limits before they are drained away as waste liquid. This system is composed of discharge units, pipe lines, and a controller. The performance of the system was assessed by comparing the calculated red ink and [sup 32]P concentrations with those monitored at six locations in the tanks. The concentration reached equilibrium after stirring 60 o 120 min with discharge units equipped with six fixed openings configured in differing directions. Residual chlorine in city water used for dilution occasionally bleached the red ink and reduced its concentration. The adsorption of [sup 32]P by slime on the walls of the tanks storing actual waste water lowered the equilibrium concentration.

  19. Friction stir welding process to repair voids in aluminum alloys

    NASA Technical Reports Server (NTRS)

    Rosen, Charles D. (Inventor); Litwinski, Edward (Inventor); Valdez, Juan M. (Inventor)

    1999-01-01

    The present invention provides an in-process method to repair voids in an aluminum alloy, particularly a friction stir weld in an aluminum alloy. For repairing a circular void or an in-process exit hole in a weld, the method includes the steps of fabricating filler material of the same composition or compatible with the parent material into a plug form to be fitted into the void, positioning the plug in the void, and friction stir welding over and through the plug. For repairing a longitudinal void (30), the method includes machining the void area to provide a trough (34) that subsumes the void, fabricating filler metal into a strip form (36) to be fitted into the trough, positioning the strip in the trough, and rewelding the void area by traversing a friction stir welding tool longitudinally through the strip. The method is also applicable for repairing welds made by a fusing welding process or voids in aluminum alloy workpieces themselves.

  20. A Brief Introduction to the Theory of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and is already an important welding process for the aerospace industry, where welds of optimal quality are demanded. The structure of welds determines weld properties. The structure of friction stir welds is determined by the flow field in the weld metal in the vicinity of the weld tool. A simple kinematic model of the FSW flow field developed at Marshall Space Flight Center, which enables the basic features of FSW microstructure to be understood and related to weld process parameters and tool design, is explained.

  1. Prediction of inclusion body solubilization from shaken to stirred reactors.

    PubMed

    Walther, Cornelia; Mayer, Sabrina; Trefilov, Alexandru; Sekot, Gerhard; Hahn, Rainer; Jungbauer, Alois; Dürauer, Astrid

    2014-01-01

    Inclusion bodies (IBs) were solubilized in a µ-scale system using shaking microtiter plates or a stirred tank reactor in a laboratory setting. Characteristic dimensionless numbers for mixing, the Phase number Ph and Reynolds number Re did not correlate with the kinetics and equilibrium of protein solubilization. The solubilization kinetics was independent of the mixing system, stirring or shaking rate, shaking diameter, and energy input. Good agreement was observed between the solubilization kinetics and yield on the µ-scale and laboratory setting. We show that the IB solubilization process is controlled predominantly by pore diffusion. Thus, for the process it is sufficient to keep the IBs homogeneously suspended, and additional power input will not improve the process. The high-throughput system developed on the µ-scale can predict solubilization in stirred reactors up to a factor of 500 and can therefore be used to determine optimal solubilization conditions on laboratory and industrial scale.

  2. Nanoscale magnetic stirring bars for heterogeneous catalysis in microscopic systems.

    PubMed

    Yang, Shuliang; Cao, Changyan; Sun, Yongbin; Huang, Peipei; Wei, Fangfang; Song, Weiguo

    2015-02-23

    Nanometer-sized magnetic stirring bars containing Pd nanoparticles (denoted as Fe3 O4 -NC-PZS-Pd) for heterogeneous catalysis in microscopic system were prepared through a facile two-step process. In the hydrogenation of styrene, Fe3 O4 -NC-PZS-Pd showed an activity similar to that of the commercial Pd/C catalyst, but much better stability. In microscopic catalytic systems, Fe3 O4 -NC-PZS-Pd can effectively stir the reaction solution within microdrops to accelerate mass transfer, and displays far better catalytic activity than the commercial Pd/C for the hydrogenation of methylene blue in an array of microdroplets. These results suggested that the Fe3 O4 -NC-PZS-Pd could be used as nanoscale stirring bars in nanoreactors.

  3. Performance Improvement of Friction Stir Welds by Better Surface Finish

    NASA Technical Reports Server (NTRS)

    Russell, Sam; Nettles, Mindy

    2015-01-01

    The as-welded friction stir weld has a cross section that may act as a stress concentrator. The geometry associated with the stress concentration may reduce the weld strength and it makes the weld challenging to inspect with ultrasound. In some cases, the geometry leads to false positive nondestructive evaluation (NDE) indications and, in many cases, it requires manual blending to facilitate the inspection. This study will measure the stress concentration effect and develop an improved phased array ultrasound testing (PAUT) technique for friction stir welding. Post-welding, the friction stir weld (FSW) tool would be fitted with an end mill that would machine the weld smooth, trimmed shaved. This would eliminate the need for manual weld preparation for ultrasonic inspections. Manual surface preparation is a hand operation that varies widely depending on the person preparing the welds. Shaving is a process that can be automated and tightly controlled.

  4. Low-voltage electrochemically stimulated stir membrane liquid-liquid microextraction as a novel technique for the determination of methadone.

    PubMed

    Ara, Katayoun Mahdavi; Raofie, Farhad

    2017-06-01

    In the present work, for the first time, a new portable setup was designed, developed and presented for the extraction of methadone, as a basic drug model from biological fluid samples using a low-voltage electrically stimulated stir membrane liquid-liquid microextraction technique (LV-ESSM-LLME), followed by high-performance liquid chromatography with ultraviolet detection. This new approach combines the advantages of stir membrane liquid-liquid microextraction and electrokinetic migration in the same unit under soft electrochemical conditions in a portable device, allowing for the isolation and preconcentration of the target analyte in a simple and efficient manner under three-phase mode. To investigate the influence of external stirring and the application of electrical potential as the driving force, a comparative study of all variables involved in the extraction process was carried out using the low-voltage electromembrane extraction (LV-EME) and LV-ESSM-LLME methods. Under soft electrokinetic migration conditions, methadone was transported from an acidic sample solution (pH 4.0), through the NPOE immobilized in the pores of the porous polypropylene sheet membrane, and into 25µL of 10mmolL(-1) HCl acceptor solution with a stirring rate of 1000rpm and 700rpm after 15min and 20min for LV-ESSM-LLME and LV-EME, respectively. Under the optimized conditions, preconcentration factors in the range of 17-24 and 21.5-29 for LV-EME and LV-ESSM-LLME, respectively, were considered, and satisfactory repeatability (4.5<[RSD]<7.5) was obtained in different matrices. The obtained relative recoveries of the target analyte were in the range of 87-94% and 93-101% for LV-EME and LV-ESSM-LLME, respectively, which indicated the excellent capability of the developed methods to extract methadone from complex matrices. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Cyromazine imprinted polymers for selective stir bar sorptive extraction of melamine in animal feed and milk samples.

    PubMed

    Fan, Wenying; Gao, Mingqi; He, Man; Chen, Beibei; Hu, Bin

    2015-06-21

    In this work, a molecularly imprinted polymer (MIP) coated stir bar was prepared using a self-designed polytetrafluoroethylene (PTFE) mold and in situ polymerization, with cyromazine as the dummy template for the target melamine. The prepared MIP coated stir bar presented a uniform and porous surface as well as good chemical stability and selectivity for melamine. Based on it, a method of MIP coated stir bar sorptive extraction (SBSE) combined with high performance liquid chromatography-ultraviolet detection (HPLC-UV) was developed for the quantification of melamine in food samples. Significant factors affecting the extraction efficiency of melamine by MIP-SBSE, such as the extraction solvent and time, stirring rate, desorption solvent and time, were investigated thoroughly. Under the optimal conditions, the analytical performance of this method was evaluated. The detection limit of the developed method was 0.54 μg L(-1) for melamine with an enrichment factor of 42-fold and the relative standard deviation (RSD) of 6.1% (c = 5 μg L(-1), n = 7), and the linear range was 2-200 μg L(-1). The established method was applied for the determination of melamine in a variety of real samples including cat food, dog food, chicken feed A, chicken feed B and milk powder, and the recoveries for melamine in the spiked samples were in the range of 76.2-98.2%, 80.0-85.5%, 89.5-113%, 85.0-95.5% and 65.0-111%, respectively. The proposed method presented a good specific recognition ability and matrix interference resistance, and was demonstrated to be effective and sensitive for the analysis of melamine in animal food and milk samples.

  6. Mechanistic Models of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Stewart, Michael B.

    1998-01-01

    Friction stir welding is a welding process developed at The Welding Institute (TWI) in England. The method uses very large strain plastic deformation of the material to join two pieces of metal together. The material is deformed using a tool which is forced between the two pieces which rotates causing a bond. Beyond this, very little is actually known although many people working in the field are willing to speculate on the detailed mechanisms involved. Some measurements made using sacrificial thermocouples at the weld joint indicate that the maximum temperature during the weld process is on the order of 370C - well below the melting temperature of the material. However, at this temperature, the material properties are highly temperature dependent, and the yield stress is approximately an order of magnitude less at this temperature than it is at room temperature. As expected, there are many interpretations of the physical mechanisms occurring during the weld process. Although there is very little published concerned with FSW, some of the anecdotal theories will be described. One describes the primary mechanism as frictional heating at the front of the tool caused by slip between the tool and the material. At elevated temperatures, the weld material becomes soft and deforms around the tool but not essentially altered by the tool rotation, similar to an extrusion. As the material meets again at the rear of the tool, the temperatures and pressures are sufficient to cause the material to bond. All other structures seen are secondary and unimportant. Another theory examined last summer at NASA's Marshall Space Flight Center (MSFC) was that there was no slip between the tool and the material resulting in a rotating mass of plastic weld material traveling at a variety of angular velocities - the greatest at the tool surface diminishing to zero at the outer edge of the plastic mass surrounding the tool. This conceptual model was followed by simplified calculations which

  7. Process Model for Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Adams, Glynn

    1996-01-01

    Friction stir welding (FSW) is a relatively new process being applied for joining of metal alloys. The process was initially developed by The Welding Institute (TWI) in Cambridge, UK. The FSW process is being investigated at NASA/MSEC as a repair/initial weld procedure for fabrication of the super-light-weight aluminum-lithium shuttle external tank. The FSW investigations at MSFC were conducted on a horizontal mill to produce butt welds of flat plate material. The weldment plates are butted together and fixed to a backing plate on the mill bed. A pin tool is placed into the tool holder of the mill spindle and rotated at approximately 400 rpm. The pin tool is then plunged into the plates such that the center of the probe lies at, one end of the line of contact, between the plates and the shoulder of the pin tool penetrates the top surface of the weldment. The weld is produced by traversing the tool along the line of contact between the plates. A lead angle allows the leading edge of the shoulder to remain above the top surface of the plate. The work presented here is the first attempt at modeling a complex phenomenon. The mechanical aspects of conducting the weld process are easily defined and the process itself is controlled by relatively few input parameters. However, in the region of the weld, plasticizing and forging of the parent material occurs. These are difficult processes to model. The model presented here addresses only variations in the radial dimension outward from the pin tool axis. Examinations of the grain structure of the weld reveal that a considerable amount of material deformation also occurs in the direction parallel to the pin tool axis of rotation, through the material thickness. In addition, measurements of the axial load on the pin tool demonstrate that the forging affect of the pin tool shoulder is an important process phenomenon. Therefore, the model needs to be expanded to account for the deformations through the material thickness and the

  8. Heat Control via Torque Control in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Venable, Richard; Colligan, Kevin; Knapp, Alan

    2004-01-01

    In a proposed advance in friction stir welding, the torque exerted on the workpiece by the friction stir pin would be measured and controlled in an effort to measure and control the total heat input to the workpiece. The total heat input to the workpiece is an important parameter of any welding process (fusion or friction stir welding). In fusion welding, measurement and control of heat input is a difficult problem. However, in friction stir welding, the basic principle of operation affords the potential of a straightforward solution: Neglecting thermal losses through the pin and the spindle that supports it, the rate of heat input to the workpiece is the product of the torque and the speed of rotation of the friction stir weld pin and, hence, of the spindle. Therefore, if one acquires and suitably processes data on torque and rotation and controls the torque, the rotation, or both, one should be able to control the heat input into the workpiece. In conventional practice in friction stir welding, one uses feedback control of the spindle motor to maintain a constant speed of rotation. According to the proposal, one would not maintain a constant speed of rotation: Instead, one would use feedback control to maintain a constant torque and would measure the speed of rotation while allowing it to vary. The torque exerted on the workpiece would be estimated as the product of (1) the torque-multiplication ratio of the spindle belt and/or gear drive, (2) the force measured by a load cell mechanically coupled to the spindle motor, and (3) the moment arm of the load cell. Hence, the output of the load cell would be used as a feedback signal for controlling the torque (see figure).

  9. Microstructural issues in a friction-stir-welded aluminum alloy

    SciTech Connect

    Flores, O.V.; Kennedy, C.; Murr, L.E.; Brown, D.; Pappu, S.; Nowak, B.M.; McClure, J.C.

    1998-02-03

    Recent observations of microstructures associated with friction-stir welding (FSW) in a number of aluminum alloys have consistently demonstrated the actual weld zone to consist of a (dynamically) recrystallized grain structure resulting from the extreme, solid-state, plastic deformation characterizing the process. Because of solubilities associated with the various precipitates in 7075 and 6061 aluminum alloys, and the fact that the precipitates were either homogeneously distributed throughout both the original (unwelded) work-piece plates and the well zones (or formed varying densities of Widmanstaetten patterns within the original and recrystallized grains), it has been difficult to follow the stirring of stable, second-phase particles from the base metal (work-piece) into the weld zone. In the present investigation, a compositionally modified 1100 aluminum alloy (nominally 99.2% Al, 0.5% Fe, 0.15% Cu, 0.12% Si, 0.05 Mn, 0.04 Ti, balance in weight percent of Be and Mg), forming a stable microdendritic (second-phase), equiaxed, cell structure was friction-stir welded. These thermally stable, geometrically specific, precipitates in the base metal were compared with their disposition within the friction-stir-weld zone. In addition, as-cast plates of this alloy were cold-rolled 50% and friction-stir-welded in order to compare these two schedules (as-cast and 50% cold-rolled) in terms of residual hardness variations and related microstructural issues as well as the effect of prior deformation on the friction-stir welding process.

  10. Dynamics of rotationally reciprocating stirred tank with planetary actuator

    NASA Astrophysics Data System (ADS)

    Prikhodko, A. A.; Smelyagin, A. I.

    2017-06-01

    The article investigates the dynamics of rotationally reciprocating stirred tank (RRST), whose actuator is the original planetary mechanism with elliptical gears. The dynamic model is constructed by reduction of driving forces, masses and moments to the reduction link (the input shaft of the actuator). The study of the resulting dynamic model was carried out by energy-mass method. As a result of the dynamic analysis we determined the necessary moment of driven forces and found the reduction link law of motion. The flywheel has been designed to ensure the required coefficient of rotation irregularity. Resulting dynamic model can be used for development and research of rotationally reciprocating stirred tanks.

  11. Characterization of the Micro Textures in a Friction Stir Weld

    NASA Technical Reports Server (NTRS)

    Schneider, Judy; Nunes, Arthur C.

    2004-01-01

    In friction stir welding (FSW), a rotating threaded pin tool is inserted into a weld seam and literally stirs the edges of the seam together. The Dynamically-Recrystallized-Zone (DXZ) of a polished and etched FSW cross-section exhibits contrasting bands (the "onion-ring" structure), the origins of which are unclear. An orientation image mapping (OIM) study suggests that the corresponding bands may correspond respectively to a "straight-through" current of metal bypassing the pin tool in a single rotation or less and a "maelstrom" current rotating a number of times around the pin tool.

  12. Seam-Tracking for Friction Stir Welded Lap Joints

    NASA Astrophysics Data System (ADS)

    Fleming, Paul A.; Hendricks, Christopher E.; Cook, George E.; Wilkes, D. M.; Strauss, Alvin M.; Lammlein, David H.

    2010-11-01

    This article presents a method for automatic seam-tracking in friction stir welding (FSW) of lap joints. In this method, tracking is accomplished by weaving the FSW tool back-and-forth perpendicular to the direction of travel during welding and monitoring force and torque signals. Research demonstrates the ability of this method to automatically track weld seam positions. Additionally, tensile and S-bend test result comparisons demonstrate that weaving most likely does not reduce weld quality. Finally, benefits of this weave-based method to FSW of lap joints are discussed and methods for incorporating it into existing friction stir welding control algorithms (such as axial load control) are examined.

  13. Friction stir weld tools having fine grain structure

    DOEpatents

    Grant, Glenn J.; Frye, John G.; Kim, Jin Yong; Lavender, Curt A.; Weil, Kenneth Scott

    2016-03-15

    Tools for friction stir welding can be made with fewer process steps, lower cost techniques, and/or lower cost ingredients than other state-of-the-art processes by utilizing improved compositions and processes of fabrication. Furthermore, the tools resulting from the improved compositions and processes of fabrication can exhibit better distribution and homogeneity of chemical constituents, greater strength, and/or increased durability. In one example, a friction stir weld tool includes tungsten and rhenium and is characterized by carbide and oxide dispersoids, by carbide particulates, and by grains that comprise a solid solution of the tungsten and rhenium. The grains do not exceed 10 micrometers in diameter.

  14. Near Net Manufacturing Using Thin Gage Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Takeshita, Jennifer; Potter, David; Holquin, Michael

    2006-01-01

    Friction Stir Welding (FSW) and near net spin forming of FSW aluminumn blanks were investigated for large-scale pressure vessel applications. With a specific focus on very thin gage 2xxx and 7xxx aluminum alloys, the program concentrated on the following: the criteria used for material selection, a potential manufacturing flow, and the effectiveness and associated risks of near net spin forming. Discussion will include the mechanical properties of the friction stir welds and the parent material from before and after the spin forming process. This effort was performed under a NASA Space Exploration initiative focused on increasing the affordability, reliability and performance of pressure vessels larger than 10 ft. diameter.

  15. FRICTION STIR SPOT WELDING OF 6016 ALUMINUM ALLOY

    SciTech Connect

    Mishra, Rajiv S.; Webb, S.; Freeney, T. A.; Chen, Y. L.; Gayden, X.; Grant, Glenn J.; Herling, Darrell R.

    2007-01-08

    Friction stir spot welding (FSSW) of 6016 aluminum alloy was evaluated with conventional pin tool and new off-center feature tools. The off-center feature tool provides significant control over the joint area. The tool rotation rate was varied between 1000 and 2500 rpm. Maximum failure strength was observed in the tool rotation range of 1200-1500 rpm. The results are interpreted in the context of material flow in the joint and influence of thermal input on microstructural changes. The off-center feature tool concept opens up new possibilities for plunge-type friction stir spot welding.

  16. Unraveling the Processing Parameters in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Schneider, Judy; Nunes, Arthur C., Jr.

    2005-01-01

    In friction stir welding (FSW), a rotating threaded pin tool is translated along a weld seam, literally stirring the edges of the seam together. To determine optimal processing parameters for producing a defect free weld, a better understanding of the resulting metal deformation flow path or paths is required. In this study, various markers are used to trace the flow paths of the metal. X-ray radiographs record the segmentation and position of the wire. Several variations in the trajectories can be differentiated within the weld zone.

  17. Generation of Protein Crystals Using a Solution-Stirring Technique

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroaki; Niino, Ai; Matsumura, Hiroyoshi; Takano, Kazufumi; Kinoshita, Takayoshi; Warizaya, Masaichi; Inoue, Tsuyoshi; Mori, Yusuke; Sasaki, Takatomo

    2004-06-01

    Crystals of bovine adenosine deaminase (ADA) were grown over a two week period in the presence of an inhibitor, whereas ADA crystals did not form using conventional crystallization methods when the inhibitor was excluded. To obtain ADA crystals in the absence of the inhibitor, a solution-stirring technique was used. The crystals obtained using this technique were found to be of high quality and were shown to have high structural resolution for X-ray diffraction analysis. The results of this study indicate that the stirring technique is a useful method for obtaining crystals of proteins that do not crystallize using conventional techniques.

  18. A facile method for the fabrication of magnetic molecularly imprinted stir-bars: A practical example with aflatoxins in baby foods.

    PubMed

    Díaz-Bao, Mónica; Regal, Patricia; Barreiro, Rocío; Fente, Cristina A; Cepeda, Alberto

    2016-11-04

    A fast and facile method for the fabrication of magnetic molecularly imprinted stir-bars (MMIP-SB) has been developed, using a combination of imprinting technology and magnetite. Magnetite was prepared in the laboratory from the raw and embedded into molecularly imprinted polymers through a process of bulk polymerization. This novel design was applied to the analysis of aflatoxins, one of the most important groups of mycotoxins in terms of occurrence and toxicity. In the context of food safety, molecularly imprinted polymers are a promising tool to achieve selective and accessible methods of extraction for different residues and contaminants. Considering the toxicity of aflatoxins, a dummy template was preferred for the synthesis of the imprinted polymers. A rapid and affordable extraction method for isolating five different aflatoxins that may be present in food was developed. The MMIP-SB was used as a conventional stir-bar and combined with high performance liquid chromatography and mass spectrometry for the determination of aflatoxin M1 in milk powder (infant formulas) and aflatoxins B1, B2, G1 and G2 in cereal-based baby foods. The results showed an average recovery of 60%, 43, 40, 44 and 39%, respectively, and RSD below 10%. These in-house prepared stir-bars featured good stirring and extraction performance, and recognition abilities, offering a good alternative to more complicated.

  19. Teaching about Inverse Functions

    ERIC Educational Resources Information Center

    Esty, Warren

    2005-01-01

    In their sections on inverses most precalculus texts emphasize an algorithm for finding f [superscript -1] given f. However, inspection of precalculus and calculus texts shows that students will never again use the algorithm, which suggests the textbook emphasis may be misplaced. Inverses appear primarily when equations need to be solved, which…

  20. A ''Voice Inversion Effect?''

    ERIC Educational Resources Information Center

    Bedard, Catherine; Belin, Pascal

    2004-01-01

    Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…

  1. A ''Voice Inversion Effect?''

    ERIC Educational Resources Information Center

    Bedard, Catherine; Belin, Pascal

    2004-01-01

    Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…

  2. Seismic Inversion Methods

    NASA Astrophysics Data System (ADS)

    Jackiewicz, Jason

    2009-09-01

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  3. Seismic Inversion Methods

    SciTech Connect

    Jackiewicz, Jason

    2009-09-16

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  4. Dewpoint temperature inversions analyzed

    NASA Technical Reports Server (NTRS)

    Ashby, W. C.; Bogner, M. A.; Moses, H.

    1969-01-01

    Dewpoint temperature inversion, with regard to other simultaneous meteorological conditions, was examined to establish the influence of meteorological variables on the variation of dewpoint temperature with height. This report covers instrumentation and available data, all the climatological features of dewpoint inversions, and specific special cases.

  5. Defect Detectability Improvement for Conventional Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Hill, Chris

    2013-01-01

    This research was conducted to evaluate the effects of defect detectability via phased array ultrasound technology in conventional friction stir welds by comparing conventionally prepped post weld surfaces to a machined surface finish. A machined surface is hypothesized to improve defect detectability and increase material strength.

  6. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Santella, M. L.; Hovanski, Yuri; Grant, Glenn J.; Carpenter, Joseph A.; Warren, C. D.; Smith, Mark T.

    2008-12-28

    Experiments are continuing to evaluate the feasibility of friction stir spot welding advanced high-strength steels including, DP780, martensitic hot-stamp boron steel, and TRIP steels. Spot weld lap-shear strengths can exceed those required by industry standards such as AWS D8.1.

  7. Friction Stir Spot Welding of DP780 Carbon Steel

    SciTech Connect

    Santella, Michael L; Hovanski, Yuri; Frederick, David Alan; Grant, Glenn J; Dahl, Michael E

    2010-01-01

    Friction stir spot welds were made in uncoated and galvannealed DP780 sheets using polycrystalline boron nitride stir tools. The tools were plunged at either a single continuous rate or in two segments consisting of a relatively high rate followed by a slower rate of shorter depth. Welding times ranged from 1 to 10 s. Increasing tool rotation speed from 800 to 1600 rev min{sup -1} increased strength values. The 2-segment welding procedures also produced higher strength joints. Average lap shear strengths exceeding 10 {center_dot} 3 kN were consistently obtained in 4 s on both the uncoated and the galvannealed DP780. The likelihood of diffusion and mechanical interlocking contributing to bond formation was supported by metallographic examinations. A cost analysis based on spot welding in automobile assembly showed that for friction stir spot welding to be economically competitive with resistance spot welding the cost of stir tools must approach that of resistance spot welding electrode tips.

  8. Temporarily alloying titanium to facilitate friction stir welding

    SciTech Connect

    Hovanski, Yuri

    2009-05-01

    While historically hydrogen has been considered an impurity in titanium, when used as a temporary alloying agent it promotes beneficial changes to material properties that increase the hot-workability of the metal. This technique known as thermohydrogen processing was used to temporarily alloy hydrogen with commercially pure titanium sheet as a means of facilitating the friction stir welding process. Specific alloying parameters were developed to increase the overall hydrogen content of the titanium sheet ranging from commercially pure to 30 atomic percent. Each sheet was evaluated to determine the effect of the hydrogen content on process loads and tool deformation during the plunge phase of the friction stir welding process. Two materials, H-13 tool steel and pure tungsten, were used to fabricate friction stir welding tools that were plunged into each of the thermohydrogen processed titanium sheets. Tool wear was characterized and variations in machine loads were quantified for each tool material and weld metal combination. Thermohydrogen processing was shown to beneficially lower plunge forces and stabilize machine torques at specific hydrogen concentrations. The resulting effects of hydrogen addition to titanium metal undergoing the friction stir welding process are compared with modifications in titanium properties documented in modern literature. Such comparative analysis is used to explain the variance in resulting process loads as a function of the initial hydrogen concentration of the titanium.

  9. Lateral position detection and control for friction stir systems

    DOEpatents

    Fleming, Paul; Lammlein, David; Cook, George E.; Wilkes, Don Mitchell; Strauss, Alvin M.; Delapp, David; Hartman, Daniel A.

    2010-12-14

    A friction stir system for processing at least a first workpiece includes a spindle actuator coupled to a rotary tool comprising a rotating member for contacting and processing the first workpiece. A detection system is provided for obtaining information related to a lateral alignment of the rotating member. The detection system comprises at least one sensor for measuring a force experienced by the rotary tool or a parameter related to the force experienced by the rotary tool during processing, wherein the sensor provides sensor signals. A signal processing system is coupled to receive and analyze the sensor signals and determine a lateral alignment of the rotating member relative to a selected lateral position, a selected path, or a direction to decrease a lateral distance relative to the selected lateral position or selected path. In one embodiment, the friction stir system can be embodied as a closed loop tracking system, such as a robot-based tracked friction stir welding (FSW) or friction stir processing (FSP) system.

  10. Stop Tobacco in Restaurants: Fifth Grade Students STIR City Hall

    ERIC Educational Resources Information Center

    Morris, Ronald Vaughan

    2008-01-01

    This article discusses a campaign called STIR: Stop Tobacco in Restaurants, that was started by fourth and fifth grade students. The goal was to end smoking in public places, including restaurants, bowling alleys, sports bars, and pool halls. For two years they motivated their peers, coordinated an information campaign to urge kids and adults to…

  11. Friction-Stir Welding of Aluminum For the Space Program

    NASA Technical Reports Server (NTRS)

    Jones, Clyde S.; Smelser, Jerry W. (Technical Monitor)

    2002-01-01

    The Marshall Space Flight Center is developing and characterizing the friction stir welding process for the Space Shuttle and other space programs. This revolutionary process, invented and patented by The Weld Institute in England, offers tremendous advantages for joining aluminum for high performance applications. It is particularly suited for advanced aluminum-lithium alloys, such as 2195, the primary structural alloy used in the External Tank. The friction stir welding process joins metals with minimal heat input, resulting in high-strength joints with high ductility. It is a simple process to demonstrate using a common milling machine for sample parts, but relatively expensive to implement on large-scale hardware, due to the high cost of tooling needed to handle the high forging pressures characteristic of the process. Recent developments at the Marshall Space Flight Center have demonstrated friction stir welding on linear joints up to 5 meters (15 ft.), with material thickness ranging between 2.5 mm and 16.5 mm (0.100" to 0.650"). High efficiency weld joints have been produced in aluminum from the 2000, 5000, and 6000 series alloy systems. A "retractable pin tool" system was patented by MSFC that allows use of friction stir welding for joints with changing material thickness, and with less rigid tooling than previously considered. This presentation will describe the details of alloys welded to-date and technical advances under development at MSFC. These developments could have substantial benefit to industrial applications for welding aluminum.

  12. Friction-Stir Welding of Aluminum For the Space Program

    NASA Technical Reports Server (NTRS)

    Jones, Clyde S.; Smelser, Jerry W. (Technical Monitor)

    2002-01-01

    The Marshall Space Flight Center is developing and characterizing the friction stir welding process for the Space Shuttle and other space programs. This revolutionary process, invented and patented by The Weld Institute in England, offers tremendous advantages for joining aluminum for high performance applications. It is particularly suited for advanced aluminum-lithium alloys, such as 2195, the primary structural alloy used in the External Tank. The friction stir welding process joins metals with minimal heat input, resulting in high-strength joints with high ductility. It is a simple process to demonstrate using a common milling machine for sample parts, but relatively expensive to implement on large-scale hardware, due to the high cost of tooling needed to handle the high forging pressures characteristic of the process. Recent developments at the Marshall Space Flight Center have demonstrated friction stir welding on linear joints up to 5 meters (15 ft.), with material thickness ranging between 2.5 mm and 16.5 mm (0.100" to 0.650"). High efficiency weld joints have been produced in aluminum from the 2000, 5000, and 6000 series alloy systems. A "retractable pin tool" system was patented by MSFC that allows use of friction stir welding for joints with changing material thickness, and with less rigid tooling than previously considered. This presentation will describe the details of alloys welded to-date and technical advances under development at MSFC. These developments could have substantial benefit to industrial applications for welding aluminum.

  13. Force measurement-based discontinuity detection during friction stir welding

    DOE PAGES

    Shrivastava, Amber; Zinn, Michael; Duffie, Neil A.; ...

    2017-02-23

    Here, the objective of this work is to develop a method for detecting the creation of discontinuities (i.e., voids, volume defects) during friction stir welding. Friction stir welding is inherently cost effective, however, the need for significant weld inspection can make the process cost prohibitive. A new approach to weld inspection is required in which an in situ characterization of weld quality can be obtained, reducing the need for postprocess inspection. To this end, friction stir welds with subsurface voids and without voids were created. The subsurface voids were generated by reducing the friction stir tool rotation frequency and increasingmore » the tool traverse speed in order to create “colder” welds. Process forces were measured during welding, and the void sizes were measured postprocess by computerized tomography (i.e., 3D X-ray imaging). Two parameters, based on frequency domain content and time-domain average of the force signals, were found to be correlated with void size. Criteria for subsurface void detection and size prediction were developed and shown to be in good agreement with experimental observations. Furthermore, with the proper choice of data acquisition system and frequency analyzer the occurrence of subsurface voids can be detected in real time.« less

  14. Recent developments in Micro Friction Stir Welding: A review

    NASA Astrophysics Data System (ADS)

    Sithole, Keydon; Vasudeva Rao, Veeredhi

    2016-02-01

    The advent of friction stir welding (FSW) in 1991 has been evolutionary in the joining of metals and related materials. Friction stir welding has enabled the joining of metals that could not be joined by other welding processes. Research has shown that dissimilar materials with very different properties, plastics, composites and even wood can be joined by FSW. Recent activities in the application of FSW has seen the development of micro friction stir welding (μFSW), which is the FSW of very thin sections of thickness 1000 μm (1 mm) or less. Micro friction stir welding further extends the applications of FSW to areas such as copper electrical contacts, tailor-welded blanks, wood. Though μFSW is relatively new development significant work has been done to date with interesting research findings being reported. This paper aims to review developments in μFSW to date. The focus of the paper will be on problems peculiar to μFSW due to downscaling to the micro scale and other practical considerations.

  15. Recovery Online

    ERIC Educational Resources Information Center

    Clark, John R.

    2007-01-01

    Since the founding of Alcoholics Anonymous (AA) in 1935, programs offering opportunity for recovery from alcoholism and other addictions have undergone vast changes. The Internet has created nearly limitless opportunities for recovering people and those seeking recovery to find both meetings and places where they can gather virtually and discuss…

  16. Recovery Online

    ERIC Educational Resources Information Center

    Clark, John R.

    2007-01-01

    Since the founding of Alcoholics Anonymous (AA) in 1935, programs offering opportunity for recovery from alcoholism and other addictions have undergone vast changes. The Internet has created nearly limitless opportunities for recovering people and those seeking recovery to find both meetings and places where they can gather virtually and discuss…

  17. The Effect of Friction on Penetration in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Rapp, Steve

    2002-01-01

    "Friction stir butt welding," as it was originally termed by Wayne Thomas and Christopher Dawes, in the early 1990s, but now commonly called "friction stir welding," has made great progress as a new welding technique. Marshall Space Flight Center has been investigating the use of FSW for assembly of the Shuttle's external fuel tank since the late 1990s and hopes to have the process in use by the summer of 2002. In FSW, a cylindrical pin tool of hardened steel, is rotated and plunged into the abutting edges of the parts to be joined. The tool is plunged into the weldment to within about .050 in of the bottom to assure full penetration. As the tool moves along the joint, the tool shoulder helps produce frictional heating, causing the material to plasticize. The metal of the two abutting plates flows from the front of the tool to the back where it cools and coalesces to form a weld in the solid phase. One quarter inch thick plates of aluminum alloy 2219 were used in this study. Two samples, each consisting of two 4 in x 12 in plates, were friction stir welded. The anvil for one sample was coated with molybdenum sulfide, while for the other sample a sheet of roughened stainless steel was placed between the anvil and the sample. The retractable pin tool was used so that the depth of the pin tool penetration could be varied. As welding proceeded, the length of the pin tool was gradually increased from the starting point. The purpose of this investigation is to find out at what point, in the down ramp, penetration occurs. Differences in root structure of the friction stir weld due to differences in anvil friction will be observed. These observations will be analyzed using friction stir weld theory.

  18. Auto-Adjustable Tool for Self-Reacting and Conventional Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor)

    2002-01-01

    A friction stir welding dcvice that is configured to perform convention friction stir welding as well as self-reacting friction stir welding is described. A pin passes hrough an upper shoulder and can selectively attach 10 and detach from a lower shoulder in a preferred embodiment. A controller maintains thc discrete position of, and/or force applied by, the upper and lower shoulders during self-reacting friction stir welding, or maintains the pin at a desired depth and/or applied force during conventional friction stir welding.

  19. Auto-Adjustable Tool for Self-Reacting and Conventional Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor)

    2002-01-01

    A friction stir welding dcvice that is configured to perform convention friction stir welding as well as self-reacting friction stir welding is described. A pin passes hrough an upper shoulder and can selectively attach 10 and detach from a lower shoulder in a preferred embodiment. A controller maintains thc discrete position of, and/or force applied by, the upper and lower shoulders during self-reacting friction stir welding, or maintains the pin at a desired depth and/or applied force during conventional friction stir welding.

  20. Preparation of dual-template molecularly imprinted polymer coated stir bar based on computational simulation for detection of fluoroquinolones in meat.

    PubMed

    Yang, Kun; Wang, Geng Nan; Liu, Hui Zhi; Liu, Jing; Wang, Jian Ping

    2017-03-01

    In this study, a dual-template molecularly imprinted polymer-coated stir bar capable of recognizing nine fluoroquinolone drugs was prepared. Its recognition abilities for fluoroquinolones and other drugs were studied by using computational simulation method. Results showed that the shape and volume of the imprinted cavities were responsible for the polymer's recognition performance. After optimization of several important parameters, a stir-bar-sorptive-extraction method was developed that was combined with high performance liquid chromatography for determination of the nine drugs in meat. The stir bar showed high enrichment factors (33-47 folds), high capture capacities (4640-4950ng) and high recoveries (>90%) for the nine drugs, and could be reused for thirty times. The limits of detection for the nine drugs were in the range of 0.1-0.3ngg(-1), and the recoveries from the fortified blank meat were in the range of 67.4%-99.0%. Therefore, this method could be used as a simple, rapid and specific tool for routine detection of residual fluoroquinolones in meat.

  1. [Optimization of stir-baking with vinegar technology for Curcumae Radix by orthogonal test].

    PubMed

    Shi, Dianhua; Su, Benzheng; Sun, Lili; Zhang, Jun; Qu, Yongsheng

    2011-05-01

    To optimize the stir-baking with vinegar technology for Curcumae Radix. The intrinsic quality (the content of Curcumin) and traditional outward appearance were chosen as indexes. The best technology was determined by orthogonal test L9 (3(4)). The factors of the moistening time, stir-baking temperature and stir-baking time were investigated. The optimal technology was as follows: the quantity of vinegar was 10%, the moistening time was 10 min, the stir-baking temperature was 130 degrees C and the stir-baking time was 10 min. The optimal stir-baking with vinegar technology for Curcumae Radix is reasonable, which can be used to guide the standardized production of Curcumae Radix stir-baked with vinegar.

  2. Preparation of a novel sorptive stir bar based on vinylpyrrolidone-ethylene glycol dimethacrylate monolithic polymer for the simultaneous extraction of diazepam and nordazepam from human plasma.

    PubMed

    Torabizadeh, Mahsa; Talebpour, Zahra; Adib, Nuoshin; Aboul-Enein, Hassan Y

    2016-04-01

    A new monolithic coating based on vinylpyrrolidone-ethylene glycol dimethacrylate polymer was introduced for stir bar sorptive extraction. The polymerization step was performed using different contents of monomer, cross-linker and porogenic solvent, and the best formulation was selected. The quality of the prepared vinylpyrrolidone-ethylene glycol dimethacrylate stir bars was satisfactory, demonstrating good repeatability within batch (relative standard deviation < 3.5%) and acceptable reproducibility between batches (relative standard deviation < 6.0%). The prepared stir bar was utilized in combination with ultrasound-assisted liquid desorption, followed by high-performance liquid chromatography with ultraviolet detection for the simultaneous determination of diazepam and nordazepam in human plasma samples. To optimize the extraction step, a three-level, four-factor, three-block Box-Behnken design was applied. Under the optimum conditions, the analytical performance of the proposed method displayed excellent linear dynamic ranges for diazepam (36-1200 ng/mL) and nordazepam (25-1200 ng/mL), with correlation coefficients of 0.9986 and 0.9968 and detection limits of 12 and 10 ng/mL, respectively. The intra- and interday recovery ranged from 93 to 106%, and the relative standard deviations were less than 6%. Finally, the proposed method was successfully applied to the analysis of diazepam and nordazepam at their therapeutic levels in human plasma. The novelty of this study is the improved polarity of the stir bar coating and its application for the simultaneous extraction of diazepam and its active metabolite, nordazepam in human plasma sample. The method was more rapid than previously reported stir bar sorptive extraction techniques based on monolithic coatings, and exhibited lower detection limits in comparison with similar methods for the determination of diazepam and nordazepam in biological fluids. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Evaluation of plating conditions for the recovery of ²¹⁰Po on a Ag planchet.

    PubMed

    Lee, Hyun Mi; Hong, Gi Hoon; Baskaran, Mark; Kim, Suk Hyun; Kim, Young Ill

    2014-08-01

    The polonium-210 in the sea and its radiological consequences have been widely studied. Current processes for (210)Po recovery from seawater vary significantly. We compared selected processes to determine optimal conditions for recovery in modestly equipped laboratories. Plating (210)Po onto a Ag planchet with constant stirring for 15 h at room temperature after preconcentration from seawater samples with Mn was preferred, achieving more than 96% recovery with 3% or less precision. Possible contaminants were masked only by ascorbic acid treatment.

  4. The inverse electroencephalography pipeline

    NASA Astrophysics Data System (ADS)

    Weinstein, David Michael

    The inverse electroencephalography (EEG) problem is defined as determining which regions of the brain are active based on remote measurements recorded with scalp EEG electrodes. An accurate solution to this problem would benefit both fundamental neuroscience research and clinical neuroscience applications. However, constructing accurate patient-specific inverse EEG solutions requires complex modeling, simulation, and visualization algorithms, and to date only a few systems have been developed that provide such capabilities. In this dissertation, a computational system for generating and investigating patient-specific inverse EEG solutions is introduced, and the requirements for each stage of this Inverse EEG Pipeline are defined and discussed. While the requirements of many of the stages are satisfied with existing algorithms, others have motivated research into novel modeling and simulation methods. The principal technical results of this work include novel surface-based volume modeling techniques, an efficient construction for the EEG lead field, and the Open Source release of the Inverse EEG Pipeline software for use by the bioelectric field research community. In this work, the Inverse EEG Pipeline is applied to three research problems in neurology: comparing focal and distributed source imaging algorithms; separating measurements into independent activation components for multifocal epilepsy; and localizing the cortical activity that produces the P300 effect in schizophrenia.

  5. Tides stir up deep Arctic heat

    NASA Astrophysics Data System (ADS)

    Green, Mattias; Rippeth, Tom; Lincoln, Ben; Lenn, Yueng; Bacon, Sheldon; Sundfjord, Arild

    2015-04-01

    The Arctic is warming at twice the rate of the rest of the planet. One of the largest sources of heat to the Arctic Ocean is the warm salty Atlantic water (AW) which enters through the Fram Strait and circulates at intermediate depth round the Arctic basin. The heat contained in the AW is sufficient to entirely melt the Arctic sea ice but is insulated from the surface by a layer of colder fresher water. Across much of the Arctic Ocean there is insufficient turbulence to drive vertical mixing, and so heat fluxes are a result of double diffusion (DD) and are consequently weak (< 0.1 W m-2). Here we present a new pan-Arctic series of direct measurements of TKE dissipation rate. The new measurements show enhanced turbulent mixing, and hence heat fluxes, over much of the continental slope around the Arctic boundary. The rate of TKE dissipation is found to increase with the bathymetric slope and vary longitudinally with the largest values to the north of Svalbard resulting in enhanced diapycnal heat fluxes over this region (20 W m-2). The observed 2-order of magnitude longitudinal variation in TKE dissipation rate correlates with the rate of dissipation of tidal energy, estimated from the local difference between the work done by the tide generating force and the tidal energy flux divergence from the TPXO8 inverse tidal solution. This correlation leads to the conclusion that the enhanced mixing observed over the continental shelf break north of Svalbard is a result of tidal processes.

  6. Applying a nonlinear, pitch-catch, ultrasonic technique for the detection of kissing bonds in friction stir welds.

    PubMed

    Delrue, Steven; Tabatabaeipour, Morteza; Hettler, Jan; Van Den Abeele, Koen

    2016-05-01

    Friction stir welding (FSW) is a promising technology for the joining of aluminum alloys and other metallic admixtures that are hard to weld by conventional fusion welding. Although FSW generally provides better fatigue properties than traditional fusion welding methods, fatigue properties are still significantly lower than for the base material. Apart from voids, kissing bonds for instance, in the form of closed cracks propagating along the interface of the stirred and heat affected zone, are inherent features of the weld and can be considered as one of the main causes of a reduced fatigue life of FSW in comparison to the base material. The main problem with kissing bond defects in FSW, is that they currently are very difficult to detect using existing NDT methods. Besides, in most cases, the defects are not directly accessible from the exposed surface. Therefore, new techniques capable of detecting small kissing bond flaws need to be introduced. In the present paper, a novel and practical approach is introduced based on a nonlinear, single-sided, ultrasonic technique. The proposed inspection technique uses two single element transducers, with the first transducer transmitting an ultrasonic signal that focuses the ultrasonic waves at the bottom side of the sample where cracks are most likely to occur. The large amount of energy at the focus activates the kissing bond, resulting in the generation of nonlinear features in the wave propagation. These nonlinear features are then captured by the second transducer operating in pitch-catch mode, and are analyzed, using pulse inversion, to reveal the presence of a defect. The performance of the proposed nonlinear, pitch-catch technique, is first illustrated using a numerical study of an aluminum sample containing simple, vertically oriented, incipient cracks. Later, the proposed technique is also applied experimentally on a real-life friction stir welded butt joint containing a kissing bond flaw.

  7. Polydimethylsiloxane/covalent triazine frameworks coated stir bar sorptive extraction coupled with high performance liquid chromatography-ultraviolet detection for the determination of phenols in environmental water samples.

    PubMed

    Zhong, Cheng; He, Man; Liao, Huaping; Chen, Beibei; Wang, Cheng; Hu, Bin

    2016-04-08

    In this work, covalent triazine frameworks (CTFs) were introduced in stir bar sorptive extraction (SBSE) and a novel polydimethylsiloxane(PDMS)/CTFs stir bar coating was prepared by sol-gel technique for the sorptive extraction of eight phenols (including phenol, 2-chlorophenol, 2-nitrophenol, 4-nitrophenol, 2,4-dimethylphenol, p-chloro-m-cresol and 2,4-dichlorophenol, 2,4,6-trichlorophenol) from environmental water samples followed by high performance liquid chromatography-ultraviolet (HPLC-UV) detection. The prepared PDMS/CTFs coated stir bar showed good preparation reproducibility with the relative standard deviations (RSDs) ranging from 3.5 to 5.7% (n=7) in one batch, and from 3.7 to 9.3% (n=7) among different batches. Several parameters affecting SBSE of eight target phenols including extraction time, stirring rate, sample pH, ionic strength, desorption solvent and desorption time were investigated. Under the optimal experimental conditions, the limits of detection (LODs, S/N=3) were found to be in the range of 0.08-0.30 μg/L. The linear range was 0.25-500 μg/L for 2-nitrophenol, 0.5-500 μg/L for phenol, 2-chlorophenol, 4-nitrophenol as well as 2,4-dimethylphenol, and 1-500 μg/L for p-chloro-m-cresol, 2,4-dichlorophenol as well as 2,4,6-trichlorophenol, respectively. The intra-day relative standard deviations (RSDs) were in the range of 4.3-9.4% (n=7, c=2 μg/L) and the enrichment factors ranged from 64.9 to 145.6 fold (theoretical enrichment factor was 200-fold). Compared with commercial PDMS coated stir bar (Gerstel) and PEG coated stir bar (Gerstel), the prepared PDMS/CTFs stir bar showed better extraction efficiency for target phenol compounds. The proposed method was successfully applied to the analysis of phenols in environmental water samples and good relative recoveries were obtained with the spiking level at 2, 10, 50 μg/L, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Analysis of preservatives with different polarities in beverage samples by dual-phase dual stir bar sorptive extraction combined with high-performance liquid chromatography.

    PubMed

    Xu, Jin; Chen, Beibei; He, Man; Hu, Bin

    2013-02-22

    A new concept of "dual-phase dual stir bar sorptive extraction (SBSE)" was proposed to simultaneously extract six preservatives with different polarities (logKo/w values of 1.27-3.41), namely, benzoic acid (BA), sorbic acid (SA), methyl p-hydroxybenzoate (MP), ethyl p-hydroxybenzoate (EP), propyl p-hydroxybenzoate (PP), and butyl p-hydroxybenzoate (BP). The dual-phase dual SBSE apparatus was consisted of two differently coated stir bars, a 3-aminopropyltriethoxysilane (APTES)-hydroxy-terminated silicone oil (OH-TSO)-coated stir bar that was prepared by sol-gel technique and a C(18) silica (C(18))-polydimethylsiloxane (PDMS)-coated stir bar that was prepared by adhesion. In dual-phase dual SBSE, the two stir bars with different coatings were placed in the same sample solution for the simultaneous extraction of the target analytes with different polarities, and then the bars were desorbed in the same desorption solvent. The extraction performance of the dual-phase dual SBSE for the six preservatives was evaluated by comparing with the conventional SBSE (individual stir bar) with different coatings, including commercial PDMS, homemade PDMS, C(18)-APTES-OH-TSO, APTES-OH-TSO, and C(18)-PDMS. The experimental results showed that the dual-phase dual SBSE had the highest extraction efficiency for the six target preservatives. Based on this fact, a novel method by combining the dual-phase dual SBSE which was consisted of the APTES-OH-TSO-coated and C(18)-PDMS-coated stir bars with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) was developed for the simultaneous analysis of six target beverage preservatives in beverages. Under optimal conditions, the limits of detection (LODs) for six target preservatives ranged from 0.6 to 2.7 μgL(-1) with the relative standard deviations (RSDs) of 4.6-9.2% (C(BA,SA)=5 μgL(-1),C(MP)=20 μgL(-1),C(EP,PP,BP)=10 μgL(-1), n=7). The enrichment factors (EFs) were approximately 16-42-fold (theoretical EF was 50-fold

  9. Alloy dissolution in argon stirred steel

    NASA Astrophysics Data System (ADS)

    Webber, Darryl Scott

    Alloying is required for the production of all steel products from small castings to large beams. Addition of large quantities of bulk alloys can result in alloy segregation and inconsistent alloy recovery. The objective of this research was to better understand alloy dissolution in liquid steel especially as it relates to Missouri S&Ts' patented continuous steelmaking process. A 45-kilogram capacity ladle with a single porous plug was used to evaluate the effect of four experimental factors on alloy dissolution: alloy species, alloy size or form, argon flow rate, and furnace tap temperature. Four alloys were tested experimentally including Class I low carbon ferromanganese, nickel and tin (as a surrogate for low melting alloys) and Class II ferroniobium. The alloys ranged in size and form from granular to 30 mm diameter lumps. Experimental results were evaluated using a theoretically based numerical model for the steel shell period, alloy mixing (Class I) and alloy dissolution (Class II). A CFD model of the experimental ladle was used to understand steel motion in the ladle and to provide steel velocity magnitudes for the numerical steel shell model. Experiments and modeling confirmed that smaller sized alloys have shorter steel shell periods and homogenize faster than larger particles. Increasing the argon flow rate shortened mixing times and reduced the delay between alloy addition and the first appearance of alloy in the melt. In addition, for every five degree increase in steel bath temperature the steel shell period was shortened by approximately four percent. Class II ferroniobium alloy dissolution was an order of magnitude slower than Class I alloy mixing.

  10. Novel molecularly imprinted stir bar sorptive extraction based on an 8-electrode array for preconcentration of trace exogenous estrogens in meat.

    PubMed

    Qiao, Li; Gan, Ning; Wang, Jiayu; Gao, Huiju; Hu, Futao; Wang, Hongfei; Li, Tianhua

    2015-01-01

    A novel 8-electrode array as stir bar was designed for selective extraction of trace level exogenous estrogens from food samples, followed by liquid desorption and HPLC-photodiode array detection. The array consisted of 8 screen-printed electrodes and each electrode was modified with Fe3O4@meso-/macroporous TiO2 microspheres and molecularly imprinted film (m-TiMIF). The fabrication of the imprinted film coating was very simple without organic solvents and chemical grafting. Both bisphenol A (BPA) and diethylstilbestrol (DES) were employed as templates in m-TiMIF fabrication in order to enrich both targets simultaneously. Interestingly, the imprinted stir bar array showed higher extraction capacity and selectivity for BPA and DES than the non-imprinted counterpart. Meanwhile, it exhibited fast adsorption and desorption kinetics due to increased mass transport in the ultra-thin film. Importantly, the m-TiMIF coating was robust enough for at least 20 uses without obvious alteration in extraction performance. The main parameters affecting the extraction efficiency, including stir speeding, sample pH, ionic strength, extraction time, desorption solvent and time, were optimized. Under optimal experimental conditions, the limits of detection (S/N=3) of the developed method were 0.28 and 0.47 μg L(-1) for BPA and DES respectively, with enrichment factors of 32.6 and 52.8-fold. The linear ranges were 3.0-1500 μg L(-1) and 4.0-1500 μg L(-1) for BPA and DES, respectively. The m-TiMIF-coating conferred better recovery and selectivity, compared with the commercial stir bar coating. The new method was successfully applied to assess BPA and DES in pork and chicken samples with satisfactory recovery.

  11. Effect of friction stir welding parameters on defect formation

    NASA Astrophysics Data System (ADS)

    Tarasov, S. Yu.; Rubtsov, V. E.; Eliseev, A. A.; Kolubaev, E. A.; Filippov, A. V.; Ivanov, A. N.

    2015-10-01

    Friction stir welding is a perspective method for manufacturing automotive parts, aviation and space technology. One of the major problems is the formation of welding defects and weld around the welding zone. The formation of defect is the main reason failure of the joint. A possible way to obtain defect-free welded joints is the selection of the correct welding parameters. Experimental results describing the effect of friction stir welding process parameters on the defects of welded joints on aluminum alloy AMg5M have been shown. The weld joint defects have been characterized using the non-destructive radioscopic and ultrasound phase array methods. It was shown how the type and size of defects determine the welded joint strength.

  12. Tracing Material Flow Paths in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Sanders, Johnny; Schneider, Judy; Numes, Arthur, Jr.

    2005-01-01

    Heat and mechanical work are coupled in the friction stir welding process. The process variables are RPM, translational weld speed, and downward plunge force. The strain-temperature history of a metal element at each point on the cross-section of the weld is determined by the process variables plus the individual flow path taken by the particular filament of metal flowing around the tool and ending on flat point. The strain-temperature history determines the properties of a metal element on the weld cross-section. The strain-temperature history is carefully controlled in metal processes where direct control is feasible. Indirect estimates of the flow paths and the strain-temperature histories of filaments comprising friction stir welds can be made from a model, if the model is good enough. This paper describes marker studies of flow path geometries for various process parameters. Observed geometries are compared with geometries estimated from models.

  13. Low-temperature friction-stir welding of 2024 aluminum

    SciTech Connect

    Benavides, S.; Li, Y.; Murr, L.E.; Brown, D.; McClure, J.C.

    1999-09-10

    Solid-state, friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction (proportional to the product of strain and strain-rate) will all influence both the recrystallization and grain growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low-temperature welding. This study compares the residual grain sizes and microstructures in 2024 Al friction-stir welded at room temperature ({approximately} 30 C) and low temperature ({minus} 30 C).

  14. A stirred bath technique for diffusivity measurements in cell matrices.

    PubMed

    Chresand, T J; Dale, B E; Hanson, S L; Gillies, R J

    1988-10-05

    A stirred bath technique was developed for determining effective diffusivities in cell matrices. The technique involves cell immobilization in a dilute gel which has negligible effect on solute diffusion. Agar and collagen were tested as immobilizing gels. Agar gel was shown to have minor interactions with the diffusion of various biological molecules, and was used for immobilization of Ehrlich Ascites Tumor (EAT) cells. Diffusivities of glucose and lactic acid were measured in EAT matrices for cell loadings between 20 and 45 vol %. Treatment with glutaraldehyde was effective in quenching the metabolic activity of the cells while preserving their physical properties and diffusive resistance. The measured data agree favorably with predictions based on Maxwell's equation for effective diffusion in a periodic composite material. The stirred bath technique is useful for diffusivity determinations in immobilized matrices or free slurries, and is applicable to both microbial and mammalian cell systems.

  15. Enabling Dissimilar Material Joining Using Friction Stir Scribe Technology

    DOE PAGES

    Hovanski, Yuri; Upadyay, Piyush; Kleinbaum, Sarah; ...

    2017-04-05

    One challenge in adapting welding processes to dissimilar material joining is the diversity of melting temperatures of the different materials. Although the use of mechanical fasteners and adhesives have mostly paved the way for near-term implementation of dissimilar material systems, these processes only accentuate the need for low-cost welding processes capable of impartially joining dissimilar material components regardless of alloy, properties, or melting temperature. Friction stir scribe technology was developed to overcome the challenges of joining dissimilar material components where melting temperatures vary greatly, and properties and/or chemistry are not compatible with more traditional welding processes. Finally, although the frictionmore » stir scribe process is capable of joining dissimilar metals and metal/polymer systems, a more detailed evaluation of several aluminum/steel joints is presented herein to demonstrate the ability to both chemically and mechanically join dissimilar materials.« less

  16. Predicting the forming limit of friction stir welded blanks

    NASA Astrophysics Data System (ADS)

    Ramulu, Perumalla Janaki; Narayanan, R. Ganesh

    2011-05-01

    Friction stir welded blanks (FSWB) are tailored blanks made by friction stir welding of sheets of different thicknesses and quality. In order to reduce the trial-and-error principles and costs, the computational simulation of stamping processes of FSW blanks is required for which a feasible methodology or theory to evaluate the forming characteristics has to be incorporated. In the present work, the validity of effective strain rate based necking criterion (ESRC) in both original and modified forms to predict the forming limit of FSW blanks made of AA6111, DP590 is analyzed. The FLC thus predicted is compared with FLC from thickness gradient based necking criterion and from literature. It is found from the validation done with literature results that a consistent and accurate forming limit prediction is obtained from modified ESRC when compared to original ESRC. The failure pattern prediction is also agreeing well with the literature results.

  17. Tracing Material Flow Paths in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Sanders, Johnny; Schneider, Judy; Numes, Arthur, Jr.

    2005-01-01

    Heat and mechanical work are coupled in the friction stir welding process. The process variables are RPM, translational weld speed, and downward plunge force. The strain-temperature history of a metal element at each point on the cross-section of the weld is determined by the process variables plus the individual flow path taken by the particular filament of metal flowing around the tool and ending on flat point. The strain-temperature history determines the properties of a metal element on the weld cross-section. The strain-temperature history is carefully controlled in metal processes where direct control is feasible. Indirect estimates of the flow paths and the strain-temperature histories of filaments comprising friction stir welds can be made from a model, if the model is good enough. This paper describes marker studies of flow path geometries for various process parameters. Observed geometries are compared with geometries estimated from models.

  18. Electromagnetic stirring with alternating current during electroslag remelting

    NASA Astrophysics Data System (ADS)

    Mitchell, Alec; Hernandez-Morales, Bernardo

    1990-08-01

    An alternating current (AC)-operated electromagnetic stirring (EMS) device, using line frequency, was designed and built to operate on a laboratory electroslag remelting (ESR) furnace for 150-mm-diameter ingots. Laboratory-scale experiments were conducted employing both 4340 alloy steel and INCONEL 718 alloy as electrode material. The initiation of stirring is accompanied by a thin strip of segregated material and favors the formation of spot segregation. Changes produced in the fluid flow conditions in the liquid pool ahead of the solidification front result in a transition from a highly directional columnar to an unoriented, branched structure. Except for small pockets of segregated liquid, the flow of molten metal does not penetrate into the mushy zone. Both electrode material and molten metal pool shape play an important role on the extent of promoting an equiaxed structure.

  19. Enabling Dissimilar Material Joining Using Friction Stir Scribe Technology

    NASA Astrophysics Data System (ADS)

    Hovanski, Yuri; Upadyay, Piyush; Kleinbaum, Sarah; Carlson, Blair; Boettcher, Eric; Ruokolainen, Robert

    2017-04-01

    One challenge in adapting welding processes to dissimilar material joining is the diversity of melting temperatures of the different materials. Although the use of mechanical fasteners and adhesives have mostly paved the way for near-term implementation of dissimilar material systems, these processes only accentuate the need for low-cost welding processes capable of impartially joining dissimilar material components regardless of alloy, properties, or melting temperature. Friction stir scribe technology was developed to overcome the challenges of joining dissimilar material components where melting temperatures vary greatly, and properties and/or chemistry are not compatible with more traditional welding processes. Although the friction stir scribe process is capable of joining dissimilar metals and metal/polymer systems, a more detailed evaluation of several aluminum/steel joints is presented herein to demonstrate the ability to both chemically and mechanically join dissimilar materials.

  20. FRICTION STIR LAP WELDING OF ALUMINUM - POLYMER USING SCRIBE TECHNOLOGY

    SciTech Connect

    Upadhyay, Piyush; Hovanski, Yuri; Fifield, Leonard S.; Simmons, Kevin L.

    2015-02-16

    Friction Stir Scribe (FSS) technology is a relatively new variant of Friction Stir Welding (FSW) which enables lap joining of dissimilar material with very different melting points and different high temperature flow behaviors. The cutter scribe attached at the tip of FSW tool pin effectively cuts the high melting point material such that a mechanically interlocking feature is created between the dissimilar materials. The geometric shape of this interlocking feature determines the shear strength attained by the lap joint. This work presents first use of scribe technology in joining polymers to aluminum alloy. Details of the several runs of scribe welding performed in lap joining of ~3.175mm thick polymers including HDPE, filled and unfilled Nylon 66 to 2mm thick AA5182 are presented. The effect of scribe geometry and length on weld interlocking features is presented along with lap shear strength evaluations.

  1. Reaction enhancement of point sources due to vortex stirring.

    PubMed

    Crimaldi, John P; Hartford, Jillian R; Weiss, Jeffrey B

    2006-07-01

    We investigate a class of reactive advection-diffusion problems motivated by an ecological mixing process. We use analytical and numerical methods to determine reaction rates between two initially distinct scalar point masses that are separated from one another by a third (nonreactive) scalar. The scalars are stirred by a single two-dimensional vortex in a variety of geometrical configurations. We show that the aggregate second-order reaction rate in the low-concentration limit is enhanced by the instantaneous stirring processes, relative to the rate predicted by an equivalent eddy diffusivity. The peak reaction rate grows as P(1/3), and the time to reach the peak decreases as P(-2/3), where P is the Péclet number. The results of this study have important implications not only for ecological modeling, but for the general understanding of turbulent reactive flows.

  2. Path Force Control for Friction Stir Welding Processes (Preprint)

    DTIC Science & Technology

    2009-02-01

    maintained, even in the presence of gaps, and wormhole generation during the welding process is eliminated by regulating the path force. 15. SUBJECT... wormhole generation during the welding process is eliminated by regulating the path force. INTRODUCTION Friction Stir Welding (FSW) is a new solid...the force in the direction of tool motion) is regulated. It will be seen that wormholes can be eliminated by regulating the path force

  3. Feasibility of Underwater Friction Stir Welding of Hardenable Alloy Steel

    DTIC Science & Technology

    2010-12-01

    bead-on-plate FSW traverses, approximately 64 inches (1.6 m) in total length, on 0.25 inch (6.4 mm) thick plates of a hardenable alloy steel . The...base plate. Based on preliminary findings, FSW of hardenable alloy steel is a feasible process and should be further researched and refined. 15...v ABSTRACT The objective of this thesis is to determine whether friction stir welding ( FSW ) is a feasible welding process for steels in an

  4. Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates

    NASA Technical Reports Server (NTRS)

    Petter, George E.; Figert, John D.; Rybicki, Daniel J.; Burns, Timothy

    2006-01-01

    A method of heat treatment has been developed to reverse some of the deleterious effects of friction stir welding of plates of aluminum alloy 7050. This alloy is considered unweldable by arc and high-energy-density beam fusion welding processes. The alloy can be friction stir welded, but as-welded workpieces exhibit low ductility, low tensile and yield strengths, and low resistance to stress corrosion cracking. Heat treatment according to the present method increases tensile and yield strengths, and minimizes or eliminates stress corrosion cracking. It also increases ductility. This method of heat treatment is a superior alternative to a specification-required heat treatment that caused the formation of large columnar grains, which are undesired. Workpieces subjected to the prior heat treatment exhibited elongations <2 percent, and standard three-point bend specimens shattered. The development of the present heat treatment method was guided partly by the principles that (1) by minimizing grain sizes and relieving deformation stresses, one can minimize or eliminate stress corrosion cracking and (2) the key to maximizing strength and eliminating residual stresses is to perform post-weld solution heating for as long a time as possible while incurring little or no development of large columnar grains in friction stir weld nuggets. It is necessary to perform some of the solution heat treatment (to soften the alloy and improve machine welding parameters) before welding. The following is an example of thickness- dependent pre- and post-weld heat treatments according to the present method: For plates 0.270 in. (approx.6.86 mm) thick milled from plates 4.5 in. (114.3 mm) thick, perform pre-weld solution heating at 890 F (477 C) for 1 hour, then cool in air. After friction stir welding, perform solution heating for 10 minutes, quench, hold at room temperature for 96 hours, then age at 250 F (121 C) for 5 hours followed by 325 F (163 C) for 27 hours.

  5. Oxide Evolution in ODS Steel Resulting From Friction Stir Welding

    DTIC Science & Technology

    2014-06-01

    pattern showing Yttrium Aluminum Monoclinic (YAM), from [12]. ...........................5  Figure 3.  MA956 Base metal stress-strain curve at high...Diagram of friction stir welding tool applied to metal , from [15]. ..................11  Figure 6.  Measured temperatures moving away from the tool pin in...a) Both yttrium oxide phases, (b) YAG and (c) YAP. ..............................56  Figure 39.  The spectrum for the base metal where no particles

  6. Meeting Report: From Stirring to Mixing in a Stratified Ocean

    DTIC Science & Technology

    2001-01-19

    ocean circulation models , J. Phys. Oceanogr., 20, 150-155, 1990. Jim~nez, J., Turbulence . In Developments in Fluid Mechanics, ed. G.K. Batchelor, K...scalar is stirred and mixed in a scalar is related by a tensor to the local gradient of the turbulent flow (Eckart, 1948). At first, during the...dynami- system using the potential density instead. cal systems theory, (3) inertial instability, submesoscale These results are purely kinematic

  7. Development of a sensitive determination method for benzotriazole UV stabilizers in enviromental water samples with stir bar sorption extraction and liquid desorption prior to ultra-high performance liquid chromatography with tandem mass spectrometry.

    PubMed

    Montesdeoca-Esponda, Sarah; del Toro-Moreno, Adrián; Sosa-Ferrera, Zoraida; Santana-Rodríguez, José Juan

    2013-07-01

    Benzotriazole UV stabilizers are emerging compounds used in personal care products and can enter surface water after passing through wastewater treatment plants without being removed. Because these analytes are strongly hydrophobic, there is an environmental risk of accumulation in solid matrices and magnification through the trophic chain. In this work, a method based on stir bar sorption extraction with liquid desorption is presented for the extraction of benzotriazole UV stabilizers from water samples. Stir bar sorptive extraction was combined with ultra-high performance LC with MS/MS detection. All important factors affecting the stir bar sorptive extraction procedure are discussed, and the optimized method was applied to seawater and wastewater samples from Gran Canaria Island, providing good selectivity and sensitivity with LODs and limits of quantification in the range of 18.4-55.1 and 61.5-184 ng/L, respectively. Recoveries between 68.4-92.2% were achieved for the more polar compounds, whereas the recoveries were lower for the two less polar compounds, most likely due to their strong absorption into the polydimethylsiloxane stir bar phase that does not allows the complete desorption. The repeatability studies gave RSDs of between 6.45 and 12.6% for all compounds in the real samples.

  8. A Review of Permanent Magnet Stirring During Metal Solidification

    NASA Astrophysics Data System (ADS)

    Zeng, Jie; Chen, Weiqing; Yang, Yindong; Mclean, Alexander

    2017-08-01

    Rather than using conventional electromagnetic stirring (EMS) with three-phase alternating current, permanent magnet stirring (PMS), based on the use of sintered NdFeB material which has excellent magnetic characteristics, can be employed to generate a magnetic field for the stirring of liquid metal during solidification. Recent experience with steel casting indicates that PMS requires less than 20 pct of the total energy compared with EMS. Despite the excellent magnetic density properties and low power consumption, this relatively new technology has received comparatively little attention by the metal casting community. This paper reviews simulation modeling, experimental studies, and industrial trials of PMS conducted during recent years. With the development of magnetic simulation software, the magnetic field and associated flow patterns generated by PMS have been evaluated. Based on the results obtained from laboratory experiments, the effects of PMS on metal solidification structures and typical defects such as surface pinholes and center cavities are summarized. The significance of findings obtained from trials of PMS within the metals processing sector, including the continuous casting of steel, are discussed with the aim of providing an overview of the relevant parameters that are of importance for further development and industrial application of this innovative technology.

  9. On the potentialities of intensification of electromagnetic stirring of melts

    NASA Astrophysics Data System (ADS)

    Branover, H.; Golbraikh, E.; Kapusta, A.; Mikhailovich, B.; Dardik, I.; Thompson, R.; Lesin, S.; Khavkin, M.

    2006-09-01

    The effciency of technological processes of producing metals and alloys, continuous ingots and castings of ferrous and non­ferrous metals is mainly determined by the intensity of heat and mass transfer in the liquid phase. To increase the latter, various methods are used, including electromagnetic ones. Most electromagnetic methods are based on the application of electromagnetic fields, harmonically varying in time. In this case, the mean velocity of metal motion is a determining parameter. Since the process of stirring is directly connected with the turbulence level in the flow, the latter is also determined by the mean velocity value. In the present paper, we set forth the results of the studies of liquid metal flows in anharmonic rotating magnetic fields generated by amplitude­modulated alter­ native currents in inductor coils. As demonstrated below, changes in modulation parameters lead to the appearance of additional degrees of freedom in the control of turbulent flows of liquid metals and expand the potentialities for controlling the processes of stirring. With a suitable choice of the modulation parameters, we can considerably increase the intensity of melt stirring at the expense of increased turbulent transfer intensity due to the excitation of the so­called forced turbulence, without increasing the mean velocity of convective flows. Thus, in this case, a more intense mixing can be achieved due to a more intense turbulent transfer at a reduced mean velocity (convective transfer). Figs 4, Refs 4.

  10. Thermo-Mechanical Processing in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Schneider, Judy

    2003-01-01

    Friction stir welding is a solid-phase joining, or welding process that was invented in 1991 at The Welding Institute (TWI). The process is potentially capable of joining a wide variety of aluminum alloys that are traditionally difficult to fusion weld. The friction stir welding (FSW) process produces welds by moving a non-consumable rotating pin tool along a seam between work pieces that are firmly clamped to an anvil. At the start of the process, the rotating pin is plunged into the material to a pre-determined load. The required heat is produced by a combination of frictional and deformation heating. The shape of the tool shoulder and supporting anvil promotes a high hydrostatic pressure along the joint line as the tool shears and literally stirs the metal together. To produce a defect free weld, process variables (RPM, transverse speed, and downward force) and tool pin design must be chosen carefully. An accurate model of the material flow during the process is necessary to guide process variable selection. At MSFC a plastic slip line model of the process has been synthesized based on macroscopic images of the resulting weld material. Although this model appears to have captured the main features of the process, material specific interactions are not understood. The objective of the present research was to develop a basic understanding of the evolution of the microstructure to be able to relate it to the deformation process variables of strain, strain rate, and temperature.

  11. New Materials Design Through Friction Stir Processing Techniques

    SciTech Connect

    Buffa, G.; Fratini, L.; Shivpuri, R.

    2007-04-07

    Friction Stir Welding (FSW) has reached a large interest in the scientific community and in the last years also in the industrial environment, due to the advantages of such solid state welding process with respect to the classic ones. The complex material flow occurring during the process plays a fundamental role in such solid state welding process, since it determines dramatic changes in the material microstructure of the so called weld nugget, which affects the effectiveness of the joints. What is more, Friction Stir Processing (FSP) is mainly being considered for producing high-strain-rate-superplastic (HSRS) microstructure in commercial aluminum alloys. The aim of the present research is the development of a locally composite material through the Friction Stir Processing (FSP) of two AA7075-T6 blanks and a different material insert. The results of a preliminary experimental campaign, carried out at the varying of the additional material placed at the sheets interface under different conditions, are presented. Micro and macro observation of the such obtained joints permitted to investigate the effects of such process on the overall joint performance.

  12. The Formability of Friction Stir Welds in Automotive Stamping Environments

    SciTech Connect

    Grant, Glenn J.; Davies, Richard W.; Stephens, Elizabeth V.; wazny, scott; Kaunitz, Leon; Waldron, D.

    2005-04-01

    Automobile body and truck cab structures are composed primarily of stampings formed from monolithic and constant gage blanks. Cost and weight penalties can arrise when strength or other requirements in one small area of the part leads to the use of a material or gage that is overmatched to the needs of the rest of the stamping. Tailor Welded Blanks (TWBs) are hybrid sheet products composed of either different materials or different thickness sheets that are joined together, then subjected to a stamping operation to create a formed assembly. The strategy is employed generally to save weight and material costs in the formed assembly by placing higher strength or thicker sections only where needed. The forming or stamping process requires the joint to be severely deformed along with the parent sheets. Aluminum TWBs for automotive applications are particularly problematic because of the low formability of aluminum weld metal. Friction Stir Welding (FSW) is a process recently applied to Aluminum TWBs that has the potential to produce a higher quality weld. The current study presents data on the mechanical properties, formability, and FSW weld process parameter development for friction stir woined, aluminum, Tailor Welded Blanks. Friction stir welded TWBs can be shown to have higher formability, higher ductility, and lower defect content than many competing joining processes, and they can be fabricated at speeds appropriate for automotive manufacturing.

  13. The Formability of Friction Stir Welds in Automotive Stamping Environments

    SciTech Connect

    Grant, Glenn J.; Davies, Richard W.; Stephens, Elizabeth V.; Wazny, Scott; Kaunitz, Leon; Waldron, Douglas J.

    2006-02-01

    Automobile body and truck cab structures are composed primarily of stampings formed from monolithic and constant gage blanks. Cost and weight penalties can arise when strength or other requirements in one small area of the part leads to the use of a material or gage that is overmatched to the needs of the rest of the stamping. Tailor Welded Blanks (TWBs) are hybrid sheet products composed of either different materials or different thickness sheets that are joined together, then subjected to a stamping operation to create a formed assembly. The strategy is employed generally to save weight and material costs in the formed assembly by placing higher strength or thicker sections only where needed. The forming or stamping process requires the joint to be severely deformed along with the parent sheets. Aluminum TWBs for automotive applications are particularly problematic because of the low formability of aluminum weld metal. Friction Stir Welding (FSW) is a process recently applied to Aluminum TWBs that has the potential to produce a higher quality weld. The current study presents data on the mechanical properties, formability, and FSW weld process parameter development for friction stir welded aluminum, Tailor Welded Blanks. Friction stir welded TWBs can be shown to have higher formability, higher ductility, and lower defect content than many competing joining processes, and they can be fabricated at speeds appropriate for automotive manufacturing.

  14. Recent Developments in Friction Stir Welding of Al-alloys

    NASA Astrophysics Data System (ADS)

    Çam, Gürel; Mistikoglu, Selcuk

    2014-06-01

    The diversity and never-ending desire for a better life standard result in a continuous development of the existing manufacturing technologies. In line with these developments in the existing production technologies the demand for more complex products increases, which also stimulates new approaches in production routes of such products, e.g., novel welding procedures. For instance, the friction stir welding (FSW) technology, developed for joining difficult-to-weld Al-alloys, has been implemented by industry in manufacturing of several products. There are also numerous attempts to apply this method to other materials beyond Al-alloys. However, the process has not yet been implemented by industry for joining these materials with the exception of some limited applications. The microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature will be discussed in detail in this review. The correlations between weld parameters used during FSW and the microstructures evolved in the weld region and thus mechanical properties of the joints produced will be highlighted. However, the modeling studies, material flow, texture formation and developments in tool design are out of the scope of this work as well as the other variants of this technology, such as friction stir spot welding (FSSW).

  15. 'Inverse' temporomandibular joint dislocation.

    PubMed

    Alemán Navas, R M; Martínez Mendoza, M G

    2011-08-01

    Temporomandibular joint (TMJ) dislocation can be classified into four groups (anterior, posterior, lateral, and superior) depending on the direction of displacement and the location of the condylar head. All the groups are rare except for anterior dislocation. 'Inverse' TMJ dislocation is a bilateral anterior and superior dislocation with impaction of the mandible over the maxilla; to the authors' knowledge only two cases have previously been reported in the literature. Inverse TMJ dislocation has unique clinical and radiographic findings, which are described for this case. Copyright © 2011 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  16. Biodegradation of Fresh vs. Oven-Dried Inedible Crop Residue in a Continuously Stirred Tank Reactor

    NASA Technical Reports Server (NTRS)

    Crawford, Kamau; Strayer, Richard

    1998-01-01

    The degradation of soluble organics and mineral recovery from fresh and oven-dried biomass were compared in an Intermediate-Scale Aerobic Bioreactor (8 L working volume) to determine if drying crop residue improves performance in a continuously stirred tank reactor (CSTR). The study was conducted in an Intermediate-Scale Aerobic Bioreactor (ISAB) CSTR with dimensions of 390 mm height x 204 mm diameter. The pH in the bioreactor was controlled at 6.0, temperature at 30 C, and aeration at 7.0 L/min. Gases monitored were CO2 evolution and dissolved oxygen. Homogeneously mixed wheat cultures, used either fresh or oven-dried biomass and were leached, then placed in the ISAB for a 4-day degradation period. Studies found that mineral recovery was greater for leached oven-dried crop residue. However, after activity by the mixed microbial communities in the ISAB CSTR, there were little notable differences in the measured mineral recovery and degradation of soluble organic compounds. Degradation of soluble organic compounds was also shown to improve for leached oven-dried crop residue, but after mixing in the CSTR the degradation of the fresh biomass seemed to be slightly greater. Time for the biomass to turn in the CSTR appeared to be one factor for the experimental differences between the fresh and oven-dried biomass. Other factors, although not as defined, were the differing physical structures in the cell walls and varying microbial components of the fresh and oven-dried treatments due to changes in chemical composition after drying of the biomass.

  17. Biodegradation of Fresh vs. Oven-Dried Inedible Crop Residue in a Continuously Stirred Tank Reactor

    NASA Technical Reports Server (NTRS)

    Crawford, Kamau; Strayer, Richard

    1998-01-01

    The degradation of soluble organics and mineral recovery from fresh and oven-dried biomass were compared in an Intermediate-Scale Aerobic Bioreactor (8 L working volume) to determine if drying crop residue improves performance in a continuously stirred tank reactor (CSTR). The study was conducted in an Intermediate-Scale Aerobic Bioreactor (ISAB) CSTR with dimensions of 390 mm height x 204 mm diameter. The pH in the bioreactor was controlled at 6.0, temperature at 30 C, and aeration at 7.0 L/min. Gases monitored were CO2 evolution and dissolved oxygen. Homogeneously mixed wheat cultures, used either fresh or oven-dried biomass and were leached, then placed in the ISAB for a 4-day degradation period. Studies found that mineral recovery was greater for leached oven-dried crop residue. However, after activity by the mixed microbial communities in the ISAB CSTR, there were little notable differences in the measured mineral recovery and degradation of soluble organic compounds. Degradation of soluble organic compounds was also shown to improve for leached oven-dried crop residue, but after mixing in the CSTR the degradation of the fresh biomass seemed to be slightly greater. Time for the biomass to turn in the CSTR appeared to be one factor for the experimental differences between the fresh and oven-dried biomass. Other factors, although not as defined, were the differing physical structures in the cell walls and varying microbial components of the fresh and oven-dried treatments due to changes in chemical composition after drying of the biomass.

  18. Stir bar sorptive extraction of volatile compounds in vinegar: validation study and comparison with solid phase microextraction.

    PubMed

    Guerrero, Enrique Durán; Marín, Ramón Natera; Mejías, Remedios Castro; Barroso, Carmelo García

    2007-10-05

    Stir bar sorptive extraction was evaluated for analysing volatiles in vinegar. The procedure developed shows detection and quantitation limits, and linear ranges adequate for analysing this type of compounds. The accuracy obtained was close to 100%, with repeatability values lower than 13%. The extraction efficiency is inversely affected by the acetic acid content. Although the absolute areas decrease, the compound area/internal standard area ratio remains constant, so for quantitative analysis, the acetic acid concentration does not affect the analytical data. The method was compared with a previous SPME method. Similar performance characteristics were obtained for both methodologies, with lower detection and quantitation limits and better repeatability reproducibility values for SBSE. Both analytical methods were used to analyse a variety of vinegars. The results obtained from both methods were in agreement.

  19. Microstructural Characterization of Friction Stir Welded Aluminum-Steel Joints

    NASA Astrophysics Data System (ADS)

    Patterson, Erin E.; Hovanski, Yuri; Field, David P.

    2016-06-01

    This work focuses on the microstructural characterization of aluminum to steel friction stir welded joints. Lap weld configuration coupled with scribe technology used for the weld tool have produced joints of adequate quality, despite the significant differences in hardness and melting temperatures of the alloys. Common to friction stir processes, especially those of dissimilar alloys, are microstructural gradients including grain size, crystallographic texture, and precipitation of intermetallic compounds. Because of the significant influence that intermetallic compound formation has on mechanical and ballistic behavior, the characterization of the specific intermetallic phases and the degree to which they are formed in the weld microstructure is critical to predicting weld performance. This study used electron backscatter diffraction, energy dispersive spectroscopy, scanning electron microscopy, and Vickers micro-hardness indentation to explore and characterize the microstructures of lap friction stir welds between an applique 6061-T6 aluminum armor plate alloy and a RHA homogeneous armor plate steel alloy. Macroscopic defects such as micro-cracks were observed in the cross-sectional samples, and binary intermetallic compound layers were found to exist at the aluminum-steel interfaces of the steel particles stirred into the aluminum weld matrix and across the interfaces of the weld joints. Energy dispersive spectroscopy chemical analysis identified the intermetallic layer as monoclinic Al3Fe. Dramatic decreases in grain size in the thermo-mechanically affected zones and weld zones that evidenced grain refinement through plastic deformation and recrystallization. Crystallographic grain orientation and texture were examined using electron backscatter diffraction. Striated regions in the orientations of the aluminum alloy were determined to be the result of the severe deformation induced by the complex weld tool geometry. Many of the textures observed in the weld

  20. Estimating nuisance parameters in inverse problems

    NASA Astrophysics Data System (ADS)

    Aravkin, Aleksandr Y.; van Leeuwen, Tristan

    2012-11-01

    Many inverse problems include nuisance parameters which, while not of direct interest, are required to recover primary parameters. The structure of these problems allows efficient optimization strategies—a well-known example is variable projection, where nonlinear least-squares problems which are linear in some parameters can be very efficiently optimized. In this paper, we extend the idea of projecting out a subset over the variables to a broad class of maximum likelihood and maximum a posteriori likelihood problems with nuisance parameters, such as variance or degrees of freedom (d.o.f.). As a result, we are able to incorporate nuisance parameter estimation into large-scale constrained and unconstrained inverse problem formulations. We apply the approach to a variety of problems, including estimation of unknown variance parameters in the Gaussian model, d.o.f. parameter estimation in the context of robust inverse problems, and automatic calibration. Using numerical examples, we demonstrate improvement in recovery of primary parameters for several large-scale inverse problems. The proposed approach is compatible with a wide variety of algorithms and formulations, and its implementation requires only minor modifications to existing algorithms.

  1. Stirring-assisted assembly of nanowires at liquid-solid interfaces

    NASA Astrophysics Data System (ADS)

    Li, Wen-Ze; Wei, Wei; Chen, Jun-Yi; He, Ji-Xiang; Xue, Sheng-Nan; Zhang, Jing; Liu, Xia; Li, Xiang; Fu, Yu; Jiao, Yong-Hua; Zhang, Kai; Liu, Fuchun; Han, En-Hou

    2013-03-01

    The assembly of Ag nanowires on quartz substrates from suspensions of water and ethylene glycol under stirring has been investigated. The introduction of stirring makes a remarkable difference to the assembly morphology. Firstly, the surface coverage of Ag nanowires is increased by a factor of 4 (in water) and 8 (in ethylene glycol) with stirring. Secondly, the Ag nanowires assembled in the stirred ethylene glycol dispersion were highly aligned. The influence of the surface of substrates, solvents and profile of the nanowires on the alignment has been explored, which indicates that stirring is an efficient way to generate nanowire arrays. This study has revealed the great potential of the stirring-assisted assembly technique in producing structurally controlled nanoarchitectures, opening up new opportunities for manufacturing ordered nanomaterials.

  2. Inverse Gas Chromatography

    DTIC Science & Technology

    1990-09-01

    4 PHASE III: CHARACTERIZATION .......... .,. ........... * . 4 Task 1 . Inverse GLC of Selected Lots of R-45M ...................... 4 Task 2 ...129 Phase 1 %, Task 2 . Chain Branching ................. 136 SUMMARY AND CONCLUSIONS ... ,.........oa. * s *..... .* 136 REFERENCES...o*, *..... .*.......* . . *. . .,,. *... .. 45 33 Enthalpies of Solution -AI9s/kJ mol 1 for Listed Probe Solutes with lndicated Lots of Poly bd R

  3. Numerical modelling of thermal phenomenon in friction stir welding of aluminum plates

    NASA Astrophysics Data System (ADS)

    Vaira Vignesh, R.; Padmanaban, R.; Arivarasu, M.; Thirumalini, S.; Gokulachandran, J.; Sai Ram, Mutyala Sesha Satya

    2016-09-01

    Friction stir welding (FSW) is a solid state welding process with potential to join materials that are non weldable by conventional fusion welding techniques. The study of heat transfer in FSW aids in the identification of defects like flash, inadequate heat input, poor material flow and mixing etc. In this paper, transient temperature distribution during FSW of aluminum alloy AA6061-T6 was simulated using finite element modelling. The model was used to predict the peak temperature and analyse the thermal history during FSW. The effect of process parameters namely tool rotation speed, tool traverse speed (welding speed), shoulder diameter and pin diameter of tool on the temperature distribution was investigated using two level factorial design. The model results were validated using the experimental results from the published literature. It was found that peak temperature was directly proportional to tool rotation speed and shoulder diameter and inversely proportional to tool traverse speed. The effect of pin diameter on peak temperature was found to be trivial.

  4. A Transient Thermal Model for Friction Stir Weld. Part I: The Model

    NASA Astrophysics Data System (ADS)

    Zhang, X. X.; Xiao, B. L.; Ma, Z. Y.

    2011-10-01

    Current analytical thermal models for friction stir welding (FSW) are mainly focused on the steady-state condition. To better understand the FSW process, we propose a transient thermal model for FSW, which considers all the periods of FSW. A temperature-dependent apparent friction coefficient solved by the inverse solution method (ISM) is used to estimate the heat generation rate. The physical reasonableness, self-consistency, and relative achievements of this model are discussed, and the relationships between the heat generation, friction coefficient, and temperature are established. The negative feedback mechanism and positive feedback mechanism are proposed for the first time and found to be the dominant factors in controlling the friction coefficient, heat generation, and in turn the temperature. Furthermore, the negative feedback mechanism is found to be the controller of the steady-state level of FSW. The validity of the proposed model is proved by applying it to FSW of the 6061-T651 and 6063-T5 aluminum alloys.

  5. Studies of Stirring and Mixing at the Submesoscale in the Ocean: FY2013 Annual Report

    DTIC Science & Technology

    2013-09-30

    geostrophic eddy stirring exhibits a very different character near the surface than at depth. Our objective is to ferret out to what degree each of these...of kinetic and potential energy and spice variance. His results find energy spectra consistent with geostrophic turbulence theory, but variance...velocity. 3. Stirring by mesoscale straining and unbalanced submesoscale processes Stirring by a geostrophic eddy field drives a cascade of PV to the

  6. Some properties of a stir-cast Ni-Cr based dental alloy.

    PubMed

    Boswell, P G; Stevens, L

    1980-06-01

    A Ni-Cr based crown and bridge alloy has been successfully stir-cast into small investment mould spaces using a modified induction melting and casting machine. Stir-casting produced substantial improvements to the mechanical properties of the cast alloy. A model for the development of the stir-cast microstructure is described and the clinical significance of the improvements in the alloy's properties is discussed.

  7. Investigation of the Microstructure of Joints of Aluminum Alloys Produced by Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Kolubaev, E. A.

    2015-02-01

    Special features of the microstructure of joints of aluminum-magnesium and aluminum-copper alloys produced by friction stir welding are analyzed. It is demonstrated that a layered structure with ultradisperse grains is produced by friction stir welding at the center of the weld joint. An analogy is drawn between the microstructures of joints produced by friction stir welding and surface layer produced by sliding friction.

  8. Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding

    SciTech Connect

    Grant, Glenn J.; Herling, Darrell R.; Arbegast, William J.; Allen, Casey D.; Degen, Cassandra M.

    2006-12-20

    Superplastically-formed structural panels are growing in their applications in aerospace, aircraft, automotive, and other industries. Generally, monolithic sheets are employed, limiting the size and complexity of the final part. However, more complex and larger final geometries are possible if individual sheet materials can be joined together through an appropriate joining technology, then SPF formed to final shape. The primary challenge in this type of SPF fabrication has been making a joint between the sheets that will survive the SPF forming event and display the correct amount of elongation in the joint relative to the base materials being formed. Friction Stir Welding is an ideal joining technology for SPF applications because the forming response of the weld metal at SPF conditions is adjustable by selecting different weld process parameters during initial joining. This allows the SPF deformation in the weld metal to be “tuned” to the deformation of the parent sheet to prevent early failure from occurring in either the weld metal or the parent sheet due to mismatched SPF flow stresses. Industrial application of the concept of matching flow stresses is currently being pursued on a program at the Pacific Northwest National Laboratory on room temperature formed friction stir welded tailor welded blanks for heavy truck applications. Flow stress matching and process parameter “tuning” is also important in the fabrication of SPF multisheet structural panels. These panels are fabricated by joining three sheets together with alternating welds top and bottom, so that each weld penetrates only two of the three sheets. This sheet pack is then sealed with a weld seam around the outside and hot gas is introduced between the sheets through a welded tube. Under SPF conditions the sheet pack inflates to produce an internally supported structure. In this paper we presents results on an investigation into using FSW and Refill Friction Stir Spot Welding to fabricated

  9. Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities

    PubMed Central

    Wang, Haiman; Qu, Youpeng; Li, Da; Ambuchi, John J.; He, Weihua; Zhou, Xiangtong; Liu, Jia; Feng, Yujie

    2016-01-01

    A continuous stirred microbial electrochemical reactor (CSMER), comprising of a complete mixing zone (CMZ) and microbial electrochemical zone (MEZ), was used for brewery wastewater treatment. The system realized 75.4 ± 5.7% of TCOD and 64.9 ± 4.9% of TSS when fed with brewery wastewater concomitantly achieving an average maximum power density of 304 ± 31 m W m−2. Cascade utilization of organic matters made the CSMER remove a wider range of substrates compared with a continuous stirred tank reactor (CSTR), in which process 79.1 ± 5.6% of soluble protein and 86.6 ± 2.2% of soluble carbohydrates were degraded by anaerobic digestion in the CMZ and short-chain volatile fatty acids were further decomposed and generated current in the MEZ. Co-existence of fermentative bacteria (Clostridium and Bacteroides, 19.7% and 5.0%), acetogenic bacteria (Syntrophobacter, 20.8%), methanogenic archaea (Methanosaeta and Methanobacterium, 40.3% and 38.4%) and exoelectrogens (Geobacter, 12.4%) as well as a clear spatial distribution and syntrophic interaction among them contributed to the cascade degradation process in CSMER. The CSMER shows great promise for practical wastewater treatment application due to high pre-hydrolysis and acidification rate, high energy recovery and low capital cost. PMID:27270788

  10. Molecular imprinting-based micro-stir bar sorptive extraction for specific analysis of Glibenclamide in herbal dietary supplements.

    PubMed

    Wu, Xiaoli; Liu, Jie; Wu, Jinhua; Wang, Yang; Xue, Cheng; Wang, Ruoyu; Hong, Junli; Zhou, Xuemin

    2012-12-01

    A novel molecularly imprinted polymers (MIPs) coated micro-stir bar (MSB) for Glibenclamide (GM) was developed. The MIPs, with GM as template molecular and methacrylic acid as functional monomer, were synthesized at the surface of the silylated MSB that was filled with magnetic core as substrate. Computational simulation was used for the optimal selection of functional monomers and porogen. The thickness of MIPs coating for MSB was about 10 μm, the adsorption and desorption time were about 40 and 20 min, respectively. The MIPs coated MSB possessed mechanical stability, high adsorption capacity, and good selectivity for GM. To achieve the optimum extraction performance, several parameters including extraction and desorption time, stirring rate, extraction and desorption solvent were investigated. A method for the determination of GM in herbal dietary supplements by MIPs coated MSB coupled with HPLC-UV was established. The results exhibited good linear ranges of 10-6250 μg L(-1) with the low limit of detection of GM (3.05 μg L(-1)) and the good recoveries (81.9-101.4%).

  11. Physical Simulation of a Duplex Stainless Steel Friction Stir Welding by the Numerical and Experimental Analysis of Hot Torsion Tests

    NASA Astrophysics Data System (ADS)

    da Fonseca, Eduardo Bertoni; Santos, Tiago Felipe Abreu; Button, Sergio Tonini; Ramirez, Antonio Jose

    2016-09-01

    Physical simulation of friction stir welding (FSW) by means of hot torsion tests was performed on UNS S32205 duplex stainless steel. A thermomechanical simulator Gleeble 3800® with a custom-built liquid nitrogen cooling system was employed to reproduce the thermal cycle measured during FSW and carry out the torsion tests. Microstructures were compared by means of light optical microscopy and electron backscatter diffraction. True strain and strain rate were calculated by numerical simulation of the torsion tests. Thermomechanically affected zone (TMAZ) was reproduced at peak temperature of 1303 K (1030 °C), rotational speeds of 52.4 rad s-1 (500 rpm) and 74.5 rad s-1 (750 rpm), and 0.5 to 0.75 revolutions, which represent strain rate between 10 and 16 s-1 and true strain between 0.5 and 0.8. Strong grain refinement, similar to the one observed in the stir zone (SZ), was attained at peak temperature of 1403 K (1130 °C), rotational speed of 74.5 rad s-1 (750 rpm), and 1.2 revolution, which represent strain rate of 19 s-1 and true strain of 1.3. Continuous dynamic recrystallization in ferrite and dynamic recrystallization in austenite were observed in the TMAZ simulation. At higher temperature, dynamic recovery of austenite was also observed.

  12. Comparison between continuous stirred tank reactor extractor and soxhlet extractor for extraction of El-Lajjun oil shale

    SciTech Connect

    Anabtawi, M.Z.

    1996-02-01

    Extraction on El-Lajjun oil shale in a continuous stirred tank reactor extractor (CSTRE) and a Soxhlet extractor was carried out using toluene and chloroform as solvents. Solvents were recovered using two distillation stages, a simple distillation followed by a fractional distillation. Gas chromotography was used to test for the existence of trapped solvent in the yield. It was found that extraction using a CSTRE gave a 12% increase in yield on average compared with the Soxhlet extractor, and an optimum shale size of 1.0mm offered a better yield and solvent recovery for both techniques. It was also found that an optimum ratio of solvent to oil shale of 2:1 gave the best oil yield. The Soxhlet extractor was found to offer an extraction rate of 1 hour to complete extraction compared with 4 hours in a CSTRE. The yield in a CSTRE was found to increase on increase of stirring. When extraction was carried out at the boiling point of the solvents in a CSTRE, the yield was found to increase by 30% on average compared to that of extraction when the solvent was at room temperature. When toluene was used for extraction, the average amount of bitumen extracted was 0.032 g/g of oil shale and 76.4% of the solvent recovered, compared with 0.037 g/g of oil shale and 84.1% of the solvent recovered using a Soxhlet extractor.

  13. Three-dimensional (3D) visualization of endolymphatic hydrops after intratympanic injection of Gd-DTPA: optimization of a 3D-real inversion-recovery turbo spin-echo (TSE) sequence and application of a 32-channel head coil at 3T.

    PubMed

    Naganawa, Shinji; Ishihara, Shunichi; Iwano, Shingo; Sone, Michihiko; Nakashima, Tsutomu

    2010-01-01

    To enable volume visualization of endolymphatic hydrops of Ménière's disease via a volume rendering (VR) technique, a three-dimensional (3D) inversion-recovery (IR) sequence with real reconstruction (3D-real IR) sequence after intratympanic injection of Gd-DTPA was optimized for higher spatial resolution using a 32-channel head coil at 3T. Pulse sequence parameters were optimized using a diluted Gd-DTPA phantom. Then, 11 patients who had been clinically diagnosed with Ménière's disease and a patient with sudden hearing loss were scanned. Images were processed using commercially available 3D-VR software. 3D-real IR data was processed to produce endolymph and perilymph fluid volume images in different colors. 3D-CISS data was processed to generate total fluid volume images. While maintaining a comparable signal-to-noise ratio (SNR) and scan time, the voxel volume could be reduced from 0.4 x 0.4 x 2 mm(3) with a 12-channel coil to 0.4 x 0.4 x 0.8 mm(3) with a 32-channel coil. A newly-optimized protocol allowed the smooth, three-dimensional visualization of endolymphatic hydrops in all patients with Ménière's disease. Volumetrically separate visualization of endo-/perilymphatic space is now feasible in patients with Ménière's disease using an optimized 3D-real IR sequence, a 32-channel head coil, at 3T, after intratympanic administration of Gd-DTPA. This will aid the understanding of the pathophysiology of Ménière's disease. (c) 2009 Wiley-Liss, Inc.

  14. Inverse heat conduction problems

    NASA Astrophysics Data System (ADS)

    Orlande, Helcio Rangel Barreto

    We present the solution of the following inverse problems: (1) Inverse Problem of Estimating Interface Conductance Between Periodically Contacting Surfaces; (2) Inverse Problem of Estimating Interface Conductance During Solidification via Conjugate Gradient Method; (3) Determination of the Reaction Function in a Reaction-Diffusion Parabolic Problem; and (4) Simultaneous Estimation of Thermal Diffusivity and Relaxation Time with Hyperbolic Heat Conduction Model. Also, we present the solution of a direct problem entitled: Transient Thermal Constriction Resistance in a Finite Heat Flux Tube. The Conjugate Gradient Method with Adjoint Equation was used in chapters 1-3. The more general function estimation approach was treated in these chapters. In chapter 1, we solve the inverse problem of estimating the timewise variation of the interface conductance between periodically contacting solids, under quasi-steady-state conditions. The present method is found to be more accurate than the B-Spline approach for situations involving small periods, which are the most difficult on which to perform the inverse analysis. In chapter 2, we estimate the timewise variation of the interface conductance between casting and mold during the solidification of aluminum. The experimental apparatus used in this study is described. In chapter 3, we present the estimation of the reaction function in a one dimensional parabolic problem. A comparison of the present function estimation approach with the parameter estimation technique, wing B-Splines to approximate the reaction function, revealed that the use of function estimation reduces the computer time requirements. In chapter 4 we present a finite difference solution for the transient constriction resistance in a cylinder of finite length with a circular contact surface. A numerical grid generation scheme was used to concentrate grid points in the regions of high temperature gradients in order to reduce discretization errors. In chapter 6, we

  15. Determination of short chain chlorinated paraffins in water by stir bar sorptive extraction-thermal desorption-gas chromatography-triple quadrupole tandem mass spectrometry.

    PubMed

    Tölgyessy, P; Nagyová, S; Sládkovičová, M

    2017-03-08

    A simple, robust, sensitive and environment friendly method for the determination of short chain chlorinated paraffins (SCCPs) in water using stir bar sorptive extraction (SBSE) coupled to thermal desorption-gas chromatography-triple quadrupole tandem mass spectrometry (TD-GC-QqQ-MS/MS) was developed. SBSE was performed using 100mL of water sample, 20mL of methanol as a modifier, and a commercial sorptive stir bar (with 10mm×0.5mm PDMS layer) during extraction period of 16h. After extraction, the sorptive stir bar was thermally desorbed and online analysed by GC-MS/MS. Method performance was evaluated for MilliQ and surface water spiked samples. For both types of matrices, a linear dynamic range of 0.5-3.0μgL(-1) with correlation coefficients >0.999 and relative standard deviations (RSDs) of the relative response factors (RRFs) <12% was established. The limits of quantification (LOQs) of 0.06 and 0.08μgL(-1), and the precision (repeatability) of 6.4 and 7.7% (RSDs) were achieved for MilliQ and surface water, respectively. The method also showed good robustness, recovery and accuracy. The obtained performance characteristics indicate that the method is suitable for screening and monitoring and compliance checking with environmental quality standards (EQS, set by the EU) for SCCPs in surface waters.

  16. Determination of Trace Polychlorinated Biphenyls and Organochlorine Pesticides in Water Samples through Large-Volume Stir Bar Sorptive Extraction Method with Thermal Desorption Gas Chromatography.

    PubMed

    Feng, Li; Zhang, Shengjun; Zhu, Guohua; Li, Mufei; Liu, Jinsong

    2017-10-06

    A fast and sensitive analytical method based on stir bar sorptive extraction technology with gas chromatography and mass spectrometry was developed to simultaneously analyse 18 kinds of polychlorinated biphenyls and 20 kinds of organochlorine pesticides in aqueous samples. A long adsorption time and small sample volume, which are problems encountered in conventional methods of stir bar sorptive extraction, were effectively solved by simultaneously using multiple stir bars for enrichment with sequential cryofocusing and merged injection. Optimised results showed good linear coefficients in the range of 10 to 500 ng/L and the method detection limits of 0.12-2.07 ng/L for polychlorinated biphenyls and organochlorine pesticides. The recovery ratios of the spiked samples at different concentrations were between 64.7 and 111.0%, and their relative standard deviations ranged from 0.9 to 17.6%. Four types of the studied compounds were determined in Qiantang River water samples, and their contents were between 0.82 and 5.00 ng/L. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  17. Bio-processing of copper from combined smelter dust and flotation concentrate: a comparative study on the stirred tank and airlift reactors.

    PubMed

    Vakylabad, Ali Behrad; Schaffie, Mahin; Ranjbar, Mohammad; Manafi, Zahra; Darezereshki, Esmaeel

    2012-11-30

    To scrutinize the influence of the design and type of the bioreactors on the bioleaching efficiency, the bioleaching were evaluated in a batch airlift and a batch stirred tank bioreactors with mixed mesophilic and mixed moderately thermophilic bacteria. According to the results, maximum copper recoveries were achieved using the cultures in the stirred tank bioreactors. It is worth noting that the main phase of the flotation concentrate was chalcopyrite (as a primary sulphide), but the smelter dust mainly contained secondary copper sulphides such as Cu(2)S, CuS, and Cu(5)FeS(4).Under optimum conditions, copper dissolution from the combined flotation concentrate and smelter dust (as an environmental hazard) reached 94.50% in the STR, and 88.02% in the airlift reactor with moderately thermophilic, after 23 days. Also, copper extractions calculated for the bioleaching using mesophilic bacteria were 48.73% and 37.19% in the STR (stirred tank reactor) and the airlift bioreactor, respectively. In addition, the SEM/EDS, XRD, chemical, and mineralogical analyses and studies confirmed the above results.

  18. Selective Inversion of Spin-Tickling Spectra in a 13C-1H Spin System

    NASA Astrophysics Data System (ADS)

    Ishiwata, Mitsumasa

    1993-10-01

    Selective spin inversion usually produces transfer of the longitudinal magnetization in a coupled spin system. Under irradiation of a stirring-field, however, transverse ones and multiple quantum coherences can also be simultaneously transferred in this process. For a coupled 13C-1H spin system under irradiation resonant with one of the 1H lines, 13C tickling spectra are observed immediately after inversion of one component of the 13C-polarizations. Spectra thus obtained are considerably different from a simple selectively-inverted pattern of the steady-state ones. These changes depend on amplitude and frequency of the rf field, frequency and phase of the inversion pulse and inhomogeneity of the static magnetic field. The most prominent change in these spectra can be explained by transfer of zero quantum coherence, which is made in the differential form into each line of the spectra.

  19. Controlling Force and Depth in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Adams, Glynn; Loftus, Zachary; McCormac, Nathan; Venable, Richard

    2005-01-01

    Feedback control of the penetration force applied to a pin tool in friction stir welding has been found to be a robust and reliable means for controlling the depth of penetration of the tool. This discovery has made it possible to simplify depth control and to weld with greater repeatability, even on workpieces with long weld joints. Prior to this discovery, depths of penetration in friction stir welding were controlled by hard-tooled roller assemblies or by depth actuators controlled by feedback from such external sensors as linear variable-differential transformers or laser-based devices. These means of control are limited: A hard-tooled roller assembly confines a pin tool to a preset depth that cannot be changed easily during the welding process. A measurement by an external sensor is only an indirect indicative of the depth of penetration, and computations to correlate such a measurement with a depth of penetration are vulnerable to error. The present force-feedback approach exploits the proportionality between the depth and the force of penetration Unlike a depth measurement taken by an external sensor, a force measurement can be direct because it can be taken by a sensor coupled directly to the pin tool. The reading can be processed through a modern electronic servo control system to control an actuator to keep the applied penetration force at the desired level. In comparison with the older depth-control methods described above, this method offers greater sensitivity to plasticizing of the workpiece metal and is less sensitive to process noise, resulting in a more consistent process. In an experiment, a tapered panel was friction stir welded while controlling the force of penetration according to this method. The figure is a plot of measurements taken during the experiment, showing that force was controlled with a variation of 200 lb (890 N), resulting in control of the depth of penetration with a variation of 0.004 in. (0.1 mm).

  20. Retractable Pin Tools for the Friction Stir Welding Process

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Two companies have successfully commercialized a specialized welding tool developed at the Marshall Space Flight Center (MSFC). Friction stir welding uses the high rotational speed of a tool and the resulting frictional heat created from contact to crush, 'stir' together, and forge a bond between two metal alloys. It has had a major drawback, reliance on a single-piece pin tool. The pin is slowly plunged into the joint between two materials to be welded and rotated as high speed. At the end of the weld, the single-piece pin tool is retracted and leaves a 'keyhole,' something which is unacceptable when welding cylindrical objects such as drums, pipes and storage tanks. Another drawback is the requirement for different-length pin tools when welding materials of varying thickness. An engineer at the MSFC helped design an automatic retractable pin tool that uses a computer-controlled motor to automatically retract the pin into the shoulder of the tool at the end of the weld, preventing keyholes. This design allows the pin angle and length to be adjusted for changes in material thickness and results in a smooth hole closure at the end of the weld. Benefits of friction stir welding, using the MSFC retractable pin tool technology, include the following: The ability to weld a wide range of alloys, including previously unweldable and composite materials; provision of twice the fatigue resistance of fusion welds and no keyholes; minimization of material distortion; no creation of hazards such as welding fumes, radiation, high voltage, liquid metals, or arcing; automatic retraction of the pin at the end of the weld; and maintaining full penetration of the pin.

  1. Multichannel sparse spike inversion

    NASA Astrophysics Data System (ADS)

    Pereg, Deborah; Cohen, Israel; Vassiliou, Anthony A.

    2017-10-01

    In this paper, we address the problem of sparse multichannel seismic deconvolution. We introduce multichannel sparse spike inversion as an iterative procedure, which deconvolves the seismic data and recovers the Earth two-dimensional reflectivity image, while taking into consideration the relations between spatially neighboring traces. We demonstrate the improved performance of the proposed algorithm and its robustness to noise, compared to competitive single-channel algorithm through simulations and real seismic data examples.

  2. Control of Reaction Kinetics During Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Das, Shamiparna; Martinez, Nelson Y.; Mishra, Rajiv S.; Grant, Glenn J.; Jana, Saumyadeep

    2017-05-01

    Friction stir processing (FSP) was used to successfully embed galfenol particles into aluminum (AA 1100 Al) matrix uniformly. However, intermetallic layer of Al3Fe was formed around the galfenol particles. Activation energy for Al3Fe formation during FSP was estimated, and attempts were made to minimize the Al3Fe layer thickness. By changing the processing conditions, FSP successfully eliminated the intermetallic layer. Hence, FSP, in addition to microstructural control, can successfully fabricate intermetallic-free embedded regions by controlling the reaction kinetics.

  3. Fatigue Crack Growth in Peened Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Forth, Scott C.; Hatamleh, Omar

    2008-01-01

    Friction stir welding induces residual stresses that accelerates fatigue crack growth in the weld nugget. Shot peening over the weld had little effect on growth rate. Laser peening over the weld retarded the growth rate: Final crack growth rate was comparable to the base, un-welded material. Crack tunneling evident from residual compressive stresses. 2195-T8 fracture surfaces were highly textured. Texturing makes comparisons difficult as the material system is affecting the data as much as the processing. Material usage becoming more common in space applications requiring additional work to develop useful datasets for damage tolerance analyses.

  4. FRICTION STIR MICROSTRUCTURAL MODIFICATION OF INVESTMENT CAST F357

    SciTech Connect

    Jana, s.; Mishra, Rajiv S.; Chou, H. N.; Herling, Darrell R.

    2007-02-09

    A hypoeutectic Al-Si alloy has been friction stir processed in this study using various run parameter combinations. Tensile test results indicate at least three times improvement in ductility value over as-cast T6 condition because of refinement in Si particle size. Si particle size and shape has been quantified and correlated with mechanical properties. Tool rotation rate seems to have the most significant effect on properties. Higher tool rotation rate resulted in more uniform and homogeneous microstructure though some anomaly is observed at very high tool rotation rate.

  5. Friction stir welding tool and process for welding dissimilar materials

    DOEpatents

    Hovanski, Yuri; Grant, Glenn J; Jana, Saumyadeep; Mattlin, Karl F

    2013-05-07

    A friction stir welding tool and process for lap welding dissimilar materials are detailed. The invention includes a cutter scribe that penetrates and extrudes a first material of a lap weld stack to a preselected depth and further cuts a second material to provide a beneficial geometry defined by a plurality of mechanically interlocking features. The tool backfills the interlocking features generating a lap weld across the length of the interface between the dissimilar materials that enhances the shear strength of the lap weld.

  6. Production of verruculogen by Penicillium estinogenum in stirred fermenters.

    PubMed

    Day, J B; Mantle, P G; Shaw, B I

    1980-04-01

    A spectrofluorometric assay for the estimation of the tremorgenic mycotoxin verruculogen in crude mycelial extract has been devised and used to determine concentrations as low as 0.2 microgram ml-1. Verruculogen production by Penicillium estinogenum has been extended from surface culture to submerged culture in 60 1 stirred fermenters, in which the maximum cell-associated mycotoxin yield [5 mg (100 ml culture)-1] was obtained within 7 d. It was found necessary to supplement the medium (Czapek Dox broth plus 0.5% yeast extract) with calcium chloride (2%) to induce profuse sporulation (2 X 10(7) conidia ml-1).

  7. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Hovanski, Yuri; Santella, M. L.; Grant, Glenn J.

    2009-12-28

    Friction stir spot welding was used to join two advanced high-strength steels using polycrystalline cubic boron nitride tooling. Numerous tool designs were employed to study the influence of tool geometry on weld joints produced in both DP780 and a hot-stamp boron steel. Tool designs included conventional, concave shouldered pin tools with several pin configurations; a number of shoulderless designs; and a convex, scrolled shoulder tool. Weld quality was assessed based on lap shear strength, microstructure, microhardness, and bonded area. Mechanical properties were functionally related to bonded area and joint microstructure, demonstrating the necessity to characterize processing windows based on tool geometry.

  8. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Santella, Michael L; Hovanski, Yuri; Grant, Glenn J; Frederick, D Alan; Dahl, Michael E

    2009-02-01

    Friction stir spot welding was used to join two advanced high-strength steels using polycrystalline cubic boron nitride tooling. Numerous tool designs were employed to study the influence of tool geometry on weld joints produced in both DP780 and a hot-stamp boron steel. Tool designs included conventional, concave shouldered pin tools with several pin configurations; a number of shoulderless designs; and a convex, scrolled shoulder tool. Weld quality was assessed based on lap shear strength, microstructure, microhardness, and bonded area. Mechanical properties were functionally related to bonded area and joint microstructure, demonstrating the necessity to characterize processing windows based on tool geometry.

  9. Control of Reaction Kinetics During Friction Stir Processing

    DOE PAGES

    Das, Shamiparna; Martinez, Nelson Y.; Mishra, Rajiv S.; ...

    2017-02-17

    Friction stir processing (FSP) was used to successfully embed galfenol particles into aluminum (AA 1100 Al) matrix uniformly. But, intermetallic layer of Al3Fe was formed around the galfenol particles. We estimated the activation energy for Al3Fe formation during FSP, and attempts were made to minimize the Al3Fe layer thickness. By changing the processing conditions, FSP successfully eliminated the intermetallic layer. Therefore, FSP, in addition to microstructural control, can successfully fabricate intermetallic-free embedded regions by controlling the reaction kinetics.

  10. Micromechanical Simulation of Deformation of Friction Stir Welded Components

    NASA Astrophysics Data System (ADS)

    Sidle, B. C.; Dawson, P. R.; Boyce, D. E.

    2004-06-01

    A microstructure-based finite element formulation for the mechanical response of friction stir welded AL-6XN stainless steel is presented. The welding process generates regions of substantial variations in material state and properties that contribute to strong heterogeneities in the mechanical behavior of welded components We modeled the system with a multiscale elastoplastic formulation in which polycrystalline behavior is computed as the integrated responses of constituent crystals. Model validation is made through comparisons to post-test measurements of shape and hardness and to lattice strain measurements from in situ neutron diffraction experiments.

  11. Developing Friction Stir Welding Process Model for ICME Application

    NASA Astrophysics Data System (ADS)

    Yang, Yu-Ping

    2015-01-01

    A framework for developing a product involving manufacturing processes was developed with integrated computational materials engineering approach. The key component in the framework is a process modeling tool which includes a thermal model, a microstructure model, a thermo-mechanical, and a property model. Using friction stir welding (FSW) process as an example, development of the process modeling tool was introduced in detail. The thermal model and the microstructure model of FSW of steels were validated with the experiment data. The model can predict reasonable temperature and hardness distributions as observed in the experiment. The model was applied to predict residual stress and joint strength of a pipe girth weld.

  12. Control of Reaction Kinetics During Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Das, Shamiparna; Martinez, Nelson Y.; Mishra, Rajiv S.; Grant, Glenn J.; Jana, Saumyadeep

    2017-02-01

    Friction stir processing (FSP) was used to successfully embed galfenol particles into aluminum (AA 1100 Al) matrix uniformly. However, intermetallic layer of Al3Fe was formed around the galfenol particles. Activation energy for Al3Fe formation during FSP was estimated, and attempts were made to minimize the Al3Fe layer thickness. By changing the processing conditions, FSP successfully eliminated the intermetallic layer. Hence, FSP, in addition to microstructural control, can successfully fabricate intermetallic-free embedded regions by controlling the reaction kinetics.

  13. Phased array ultrasonic inspection of Friction Stir Weldments

    NASA Astrophysics Data System (ADS)

    Lamarre, André; Moles, Michael; Lupien, Vincent

    2000-05-01

    Phased array ultrasonic inspection methods have been developed for the rapid inspection of Friction Stir Weldments (FSW) on Delta rocket cryogenic tanks. A comprehensive review was performed to identify NDE methods that are suitable for the detection of defects in this new welding process. The search included a review of traditional and advanced NDE methods that were capable of demonstrating both the sensitivity and inspection rates required for this examination. This paper will discuss the theory behind phased array techniques, fundamentals of several probe designs for FSW configurations, and the advantages of using phased arrays over conventional NDE methods for this applications.

  14. Stir bar sorptive extraction coupled to liquid chromatography for the analysis of strobilurin fungicides in fruit samples.

    PubMed

    Campillo, Natalia; Viñas, Pilar; Aguinaga, Nerea; Férez, Gema; Hernández-Córdoba, Manuel

    2010-07-02

    A stir bar microextraction (SBSE) procedure for the determination of seven strobilurin fungicides in fruit samples using liquid chromatography (LC) and diode array detection (DAD) has been developed. The samples were sonicated in the presence of ethanol before submitting the extracts to SBSE. The incorporation of drazoxolon as an internal standard before SBSE allowed calibration without the need to use the standard additions method. Under the optimized conditions, detection limits were in the 0.3-2 ng g(-1) range, corresponding to trifloxystrobin and metominostrobin, respectively. The SBSE-LC-DAD procedure showed good repeatability (RSD below 11% in all cases) and provided recoveries of 80-105% from spiked samples. The method was applied to fifteen fruit samples, and low levels of pyraclostrobin and trifloxystrobin were found in two of them.

  15. Critical role of STIR MRI in early detection of post-streptococcal periostitis with dysproteinaemia (Goldbloom's syndrome).

    PubMed

    Papa, Riccardo; Consolaro, Alessandro; Minoia, Francesca; Caorsi, Roberta; Magnano, Gianmichele; Gattorno, Marco; Ravelli, Angelo; Picco, Paolo

    2017-01-01

    In 1966, Goldbloom et al. described two children who developed a peculiar clinical picture characterized by intermittent daily bone pain in the lower limbs, fever spikes, increased acute phase reactants and dysproteinaemia. The syndrome occurred two weeks after a group A β-haemolytic streptococcus infection. So far, only a few cases have been reported in the medical literature in English. We report two further cases of Goldbloom's syndrome with a review of the literature in English. Our two patients lived in the same Italian region and presented their syndrome onset a week apart. Early use of STIR MRI revealed an atypical metaphyseal hyperintensity in the femurs and tibias. X-ray showed periosteal hyperostosis. A short cycle of corticosteroids led to rapid recovery of symptoms and disappearance of bone changes. The reported cases highlight a likely under-recognised post-streptococcal inflammatory periosteal reaction and emphasise the diagnostic utility of the newer imaging modalities.

  16. Intersections, ideals, and inversion

    SciTech Connect

    Vasco, D.W.

    1998-10-01

    Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.

  17. [Influence of stir-baked with sand on active ingredients, diarrhea and hepatoprotection of Herpetospermum caudigerum].

    PubMed

    Li, Juan-juan; Shen, Gang; Yin, Rong-li; Shen, Cheng-ying; Cheng, Ling; Qiu, Ling; Han, Jin; Yuan, Hai-long

    2015-01-01

    To study the influence of stir-baked with sand on active ingredients, diarrhea and hepatoprotection of Herpetospermum caudigerum, the contents of herperione and herpetin in H. caudigerum before and after stir-baking with sand were analyzed by HPLC. The effect of stir-baked with sand on diarrhea of H. caudigerum TL was evaluated using the mean stool rate (MSR) and mean diarrheal index ( MDI) and the influence of stir-baked with sand on hepatoprotective effect of H. caudigerum TL was examined using a mouse model of CCl4-induced liver injury based on the analysis of serum ALT and AST activities. The results of HPLC analysis showed the content of herperione in H. caudigerum after stir-baking with sand decreased by 40.9% (P < 0.01) and the content of herpetin had no change. Pharmacodynamic results showed that the MSR and MDI of high-dose and middle-dose group of H. caudigerum TL after stir-baking with sand were significantly lower than that of high-dose and middle-dose group of H. caudigerum TL without stir-baking with sand; The high-dose and middle-dose of H. caudigerum TL with/without stir-baking with sand significantly alleviated liver injury as indicated by the decreased levels of serum ALT and AST, but the ALT and AST levels of high-dose and middle-dose group of H. caudigerum TL after stir-baking with sand were higher than that of H. caudigerum TL without stir-baking with sand. The results revealed that the stir-baking with sand could effectively relieve diarrhea effect of H. caudigerum TL, while it also reduces the hepatoprotection of H. caudigerum TL.

  18. A Numerical Simulation for Dissimilar Aluminum Alloys Joined by Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Hamilton, Carter; Kopyściański, Mateusz; Węglowska, Aleksandra; Dymek, Stanisław; Pietras, Adam

    2016-09-01

    Dissimilar aluminum alloy sheets of 2017A-T451 and 7075-T651 (6 mm thickness) were friction stir welded in a butt weld configuration. A numerical simulation of the joining process was developed to visualize the material flow patterns and temperature distribution and to correlate the microstructure to the hardness behavior. Due to the complementary downward flow of surface material into the workpiece thickness and upward flow of mid-plane and bottom-plane material, the weld nugget is composed of alternating layers of 7075 and 2017A. These layers have unique temperature histories depending on the material's initial location within the cross section; therefore, they also have distinctive precipitate distributions. Supersaturated surface material flows into the process zone and forms a core in which GP zones reprecipitate upon cooling. Mid-plane and bottom-plane material flow toward the workpiece surface and encompass the surface material core. Within this region, the weld temperatures overage the equilibrium θ phase in 2017A, decreasing the hardness, and at the same time, dissolve the equilibrium η/ T phase in the 7075, leading to reprecipitation of GP zones upon cooling and a hardness recovery.

  19. Stir bar sorptive extraction applied to the determination of dicarboximide fungicides in wine.

    PubMed

    Sandra, P; Tienpont, B; Vercammen, J; Tredoux, A; Sandra, T; David, F

    2001-08-31

    The dicarboximide fungicides vinclozolin, iprodione and procymidone were analyzed in white wines using stir bar sorptive extraction (SBSE) in combination with thermal desorption-capillary GC-MS analysis (TD-cGC-MS). The method was optimized using spiked water samples in a concentration range between 0.5 and 100 microg/l. Iprodione was measured as its degradation product 3,5-dichlorophenyl hydantoin. Limits of quantification in the full scan MS mode are 0.5 microg/l for vinclozolin and procymidone and 5 microg/l for iprodione. In the ion monitoring mode, concentrations 100 times lower can be dosed. Because of wine matrix effects on the recoveries, quantification of the target fungicides in wine had to be carried out by standard addition. For the thermolabile iprodione, the accuracy of SBSE-TD-cGC-MS was verified using SBSE followed by liquid desorption and analysis by liquid chromatography-atmospheric pressure chemical ionization mass spectroscopy. Procymidone and iprodione were detected in wines in concentrations up to 65 microg/l while the highest concentration of vinclozolin detected was smaller than 3 microg/l.

  20. A cellular automaton model for microstructural simulation of friction stir welded AZ91 magnesium alloy

    NASA Astrophysics Data System (ADS)

    Akbari, Mostafa; Asadi, Parviz; Besharati Givi, MohammadKazem; Zolghadr, Parisa

    2016-03-01

    To predict the grain size and microstructure evolution during friction stir welding (FSW) of AZ91 magnesium alloy, a finite element model (FEM) is developed based on the combination of a cellular automaton model and the Kocks  -  Mecking and Laasraoui-Jonas models. First, according to the flow stress curves and using the Kocks  -  Mecking model, the hardening and recovery parameters and the strain rate sensitivity were calculated. Next, an FEM model was established in Deform-3D software to simulate the FSW of AZ91 magnesium alloy. The results of the FEM model are used in microstructure evolution models to predict the grain size and microstructure of the weld zone. There is a good agreement between the simulated and experimental microstructures, and the proposed model can simulate the dynamic recrystallization (DRX) process during FSW of AZ91 alloy. Moreover, microstructural properties of different points in the SZ as well as the effect of the w/v parameter on the grain size and microstructure are considered.

  1. Optimization of stir bar sorptive extraction applied to the determination of odorous compounds in drinking water.

    PubMed

    Benanou, D; Acobas, F; de Roubin, M R

    2004-01-01

    The off-flavour compounds 2-methylisoborneol (MIB), geosmin, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole and 2,4,6-tribromoanisole were analyzed in water samples by Stir Bar Sorptive Extraction (SBSE) followed by on-line thermal desorption (TD)-capillary GC/MS. Quantification was performed using MS in the single ion monitoring mode (SIM) with 2,4,6-trichloroanisol-D5 as internal standard. Quantification limits are 0.1 ng/l to 0.2 ng/l for the haloanisoles, 0.5 ng/l for geosmin and 1 ng/l for MIB. The relative standard deviations at the quantification limit are ranging from 7 to 14.6%. SBSE-recovery was evaluated by spiking real water samples and varied from 87 to 117%. More than twenty samples per day can be analyzed by SBSE-TD-capillary GC-MS. The same technique in combination with olfactometry was used to elucidate unknown odorous compounds in water samples.

  2. Water compatible stir-bar devices imprinted with underivatised glyphosate for selective sample clean-up.

    PubMed

    Gomez-Caballero, Alberto; Diaz-Diaz, Goretti; Bengoetxea, Olatz; Quintela, Amaia; Unceta, Nora; Goicolea, M Aranzazu; Barrio, Ramón J

    2016-06-17

    This paper reports the development of stir bars with a new MIP based coating, for the selective sorptive extraction of the herbicide glyphosate (GLYP). Molecular imprinting of the polymer has directly been carried out employing underivatised GLYP as the template molecule. Due to the poor solubility of the target compound in organic solvents, the MIP methodology has been optimised for rebinding in aqueous media, being the synthesis and the rebinding steps carried out in water:methanol mixtures and pure aqueous media. The coating has been developed by radical polymerisation initiated by UV energy, using N-allylthiourea and 2-dimethyl aminoethyl methacrylate as functional monomers and ethylene glycol dimethacrylate as the cross-linker. Mechanical stability of the coating has been improved using 1,3-divinyltetramethyldisiloxane in the polymerisation mixture. Under the optimised conditions, the MIP has demonstrated excellent selectivity for the target compound in the presence of structural analogues, including its major metabolites. The applicability of the proposed method to real matrices has also been assessed using river water and soil samples. Registered mean recoveries ranged from 90.6 to 97.3% and RSD values were below 5% in all cases, what confirmed the suitability of the described methodology for the selective extraction and quantification of GLYP.

  3. Dual-phase twisters: a new approach to headspace sorptive extraction and stir bar sorptive extraction.

    PubMed

    Bicchi, Carlo; Cordero, Chiara; Liberto, Erica; Rubiolo, Patrizia; Sgorbini, Barbara; David, Frank; Sandra, Pat

    2005-11-11

    The fields of applicability of headspace sorptive extraction (HSSE) and stir bar sorptive extraction (SBSE) using polydimethylsiloxane (PDMS) as sorbent have been intensively discussed and widely described. One of the limits of sorptive extraction is that PDMS (i.e. an apolar phase) is the only polymer currently in use making it difficult to recover polar analytes from complex or multi-ingredient matrices and those with very volatile components (C1-C4 analytes). Dual-phase twisters are here introduced as new tools for HSSE and SBSE to overcome the above limits. Dual-phase twisters combine the concentration capabilities of two or more sampling materials operating in different ways (in this case sorption and adsorption). The new twisters consist of a short PDMS tube the ends of which are closed with two magnetic stoppers, thus creating an inner cavity that can be packed with different types of adsorbents like activated carbons. The concentration capability of dual-phase twisters was evaluated by using them for the HSSE and SBSE sampling of a number of matrices in the vegetable, food and environmental fields. The contributions made by different carbons to recovery, repeatability and intermediate precision were also investigated.

  4. [Total inversion of the uterus].

    PubMed

    Novachkov, V; Baltadzhieva, B; Ilieva, A; Rachev, E

    2008-01-01

    Non puerperal inversion of the uterus is very uncommon. Patients may present with pelvic pain, vaginal bleeding or hemodynamic shock. We report a fifty five old woman with uterus inversion second stage.

  5. Inverse Functions and their Derivatives.

    ERIC Educational Resources Information Center

    Snapper, Ernst

    1990-01-01

    Presented is a method of interchanging the x-axis and y-axis for viewing the graph of the inverse function. Discussed are the inverse function and the usual proofs that are used for the function. (KR)

  6. [Serial T2 short inversion time inversion recovery images in a patient with medullary hemorrhage].

    PubMed

    Okada, Yoko; Shibazaki, Kensaku; Iguchi, Yasuyuki; Inoue, Takeshi; Kimura, Kazumi

    2007-08-01

    A 52-year-old man was admitted to our hospital because of hypesthesia on the right side of his body. He had no medical history. On admission, he exhibited hypesthesia and disturbance of the touch and the vibratory sense on the right side of his body excluding the face. A brain T2* -weighted image revealed the a dot like lesion surrounded by an iso-signal lesion in the medial medulla oblongata. Therefore a diagnosis of medullary hemorrhage was made. Although a vascular malformation was considered as the cause of the hemorrhage, cerebral angiography did not reveal any vascular malformations. After admission, he developed left hypoglossal nerve palsy on day 6, and intractable hiccups on day 11. A T2* -weighted image and a FLAIR image disclosed edema surrounding the hematoma in the medial medullary lesion. T2* weighted images are useful for diagnosing and evaluating serial changes of medullary hemorrhage.

  7. Polyaniline/cyclodextrin composite coated stir bar sorptive extraction combined with high performance liquid chromatography-ultraviolet detection for the analysis of trace polychlorinated biphenyls in environmental waters.

    PubMed

    Lei, Yun; He, Man; Chen, Beibei; Hu, Bin

    2016-04-01

    A novel polyaniline/α-cyclodextrin (PANI/α-CD) composite coated stir bar was prepared by sol-gel process for the analysis of polychlorinated biphenyls (PCBs) in this work. The preparation reproducibility of the PANI/α-CD-coated stir bar was good, with relative standard deviations (RSDs) ranging from 2.3% to 3.7% (n=7) and 2.0% to 3.8% (n=7) for bar to bar and batch to batch, respectively. Based on it, a novel method of PANI/α-CD-coated stir bar sorptive extraction (SBSE) followed by high performance liquid chromatography-ultraviolet (HPLC-UV) detection was developed for the determination of trace PCBs in environmental waters. To obtain the best extraction performance for target PCBs, several parameters affecting SBSE, such as extraction time, stirring rate, and ionic strength were investigated. Under optimal experimental conditions, the limits of detection (LODs) of the proposed method for seven PCBs were in the range of 0.048-0.22 μg/L, and the RSDs were 5.3-9.8% (n=7, c=1 μg/L). Enrichment factors (EFs) ranging from 39.8 to 68.4-fold (theoretical EF, 83.3-fold) for target analytes were achieved. The proposed method was successfully applied for the determination of seven target PCBs in Yangtze River water and East Lake water, and the recoveries were in the range of 73.0-120% for the spiked East Lake water samples and 82.7-121% for the spiked Yangtze River water samples, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Jacket-free stir bar sorptive extraction with bio-inspired polydopamine-functionalized immobilization of cross-linked polymer on stainless steel wire.

    PubMed

    Zhang, Zixin; Zhang, Wenpeng; Bao, Tao; Chen, Zilin

    2015-08-14

    Stainless steel wire (SSW) is a good substrate for stir bar sorptive extraction (SBSE). However, it is still a challenge to immobilize commonly used cross-linked polymers onto SSW. In this work, we present a new approach for immobilization of the cross-linked organic polymer onto SSW for jacket-free SBSE. A dopamine derivative was firstly synthesized; by introducing a mussel-inspired polydopamine process, a stable coating layer was finally generated on the surface of SSW. Secondly, the cross-linked polymer was synthesized on the polydopamine-modified SSW by using acetonitrile as the porogen, acrylamide (AA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker and 2,2'-azobis (2-methylpropionitrile) as the initiator. A diluted pre-polymerization solution was carefully prepared to generate a thin layer of the polymer. The prepared poly(EGDMA-AA)-modified stir bar showed high stability and good tolerance toward stirring, ultrasonication, organic solvents, and strong acidic and basic conditions. Morphology and structure characterization of coatings were performed by scanning electron microscopy and Fourier transform infrared spectra, respectively. The prepared poly(EGDMA-AA)-modified stir bar showed great extraction efficiency toward protoberberines, with enrichment factors of 19-42. An SBSE-HPLC method was also developed for quantitative analysis of protoberberines. The method showed low limits of detection (0.06-0.15 ng mL(-1)), wide linear range (0.5-400 ng mL(-1)), good linearity (R≥0.9980) and good reproducibility (RSD≤3.60% for intra-day, RSD≤4.73% for inter-day). The developed method has been successfully applied to determine protoberberines in herb and rat plasma samples, with recoveries of 88.53-114.61%. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. A Microstructure - Processing Relationships in Friction Stir Processing (FSP) of NiAl Bronze

    DTIC Science & Technology

    2009-02-01

    during straining. Introduction An allied process of friction stir welding [1] ( FSW ), friction stir processing (FSP) is emerging as a novel metal...Robbins, O.C. Shepard and O.D. Sherby: J. Iron Steel Inst., 1964, vol. 202, pp. 804-7 22. O.D. Sherby, B. Walser, C.M. Young and E.M. Cady: Scripta

  10. Sampling of Malodorous Compounds in Air Using Stir Bar Sorbtive Extraction

    USDA-ARS?s Scientific Manuscript database

    Twisters, (poly)-dimethylsiloxane-coated magnetic stir bars, were used to measure malodorous compounds in air. In initial experiments, a minimum deployment time was determined by preloading the stir bars with 10 compounds with a range of volatilities and polarities and then monitoring their loss. ...

  11. Stirring and mixing effects on oscillations and inhomogeneities in the minimal bromate oscillator

    NASA Astrophysics Data System (ADS)

    Dutt, A. K.; Menzinger, M.

    1999-04-01

    Stirring and mixing effects on the oscillations and inhomogeneities in the bromate-bromide-cerous system (minimal bromate oscillator) have been investigated in a continuously fed stirred tank reactor (CSTR). A movable microelectrode is used to monitor the inhomogeneities inside the CSTR in an oscillating phase. The results are explained in terms of the theory of imperfect mixing.

  12. Center Segregation with Final Electromagnetic Stirring in Billet Continuous Casting Process

    NASA Astrophysics Data System (ADS)

    Jiang, Dongbin; Zhu, Miaoyong

    2017-02-01

    With a multiphase solidification model built, the effect of F-EMS parameters on center segregation was investigated in 160 mm × 160 mm billet continuous casting process. In the model, the initial growth of equiaxed grains which could move freely with liquid was treated as slurry, while the coherent equiaxed zone was regarded as porous media. The results show that the stirring velocity is not the main factor influencing center segregation improvement, which is more affected by current intensity and stirring pool width. Because solute transport is controlled by solidification rate as stirring pool width is 73 mm, center segregation declines continuously with current intensity increasing. As liquid pool width decreases to 61 mm and less latent heat needs to dissipate in the later solidification, the center segregation could be improved more obviously by F-EMS. Due to center liquid solute enrichment and liquid phase accumulation in the stirring zone, center segregation turns to rise reversely with higher current intensity and becomes more serious with stirring pool width further decreasing to 43 mm. As the stirring pool width is 25 mm, the positive segregation has already formed and solute could still concentrate with weak stirring, leading to center segregation deterioration. With the optimized current intensity (400 A) and stirring pool width (61 mm) set for continuous mode, center segregation improvement is better than that of alternative mode.

  13. Effects of Laser Peening, and Shot Peening, on Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Hatamleh, Omar; Hackel, Lloyd; Rankin, Jon; Truong, Chanh; Walter, Matt

    2006-01-01

    A viewgraph presentation describing the effects of laser peening and shot peening on friction stir welding is shown. The topics include: 1) Background; 2) Friction Stir Welding (FSW); 3) Microstructure; 4) Laser & Shot Peening; 5) Residual Stresses; 6) Tensile Behavior; 7) Fatigue Life & Surface Roughness; 8) Crack Growth; and 9) Benefits.

  14. 7 CFR 58.711 - Cheddar, colby, washed or soaked curd, granular or stirred curd cheese.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... stirred curd cheese. 58.711 Section 58.711 Agriculture Regulations of the Department of Agriculture... soaked curd, granular or stirred curd cheese. Cheese, used in the manufacture of pasteurized process cheese products should possess a pleasing and desirable taste and odor consistent with the age of the...

  15. 7 CFR 58.711 - Cheddar, colby, washed or soaked curd, granular or stirred curd cheese.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... stirred curd cheese. 58.711 Section 58.711 Agriculture Regulations of the Department of Agriculture... soaked curd, granular or stirred curd cheese. Cheese, used in the manufacture of pasteurized process cheese products should possess a pleasing and desirable taste and odor consistent with the age of the...

  16. Microstructural Investigation of Friction-Stir-Welded 7005 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Xu, Xuesong; Lu, Yan; Zheng, Feiyan; Chen, Bin

    2015-11-01

    This paper is aimed to investigate the microstructure of 7005 aluminum sheets joined by friction-stir welding as well as their mechanical properties. Specimens with ten different sets of welding parameters were studied. Tensile test and fracture analysis determined that the joint of the best quality was obtained at the rotation speed of 1000 rpm matching with the travel speed of 200 mm/min, and the travel speed has more impact on the ultimate tensile strength. Optical microscope observation was applied to this high-quality specimen and gave evidence to explaining the formation of the onion ring structure. Electron back-scattered diffraction (EBSD) technique was employed to characterize the textures and revealed the evolution of microstructures during friction stir processing. The EBSD results showed that the grains maintain their original orientations at relatively low deformation while the orientations rotate under increasing strain. Accumulated rotation will turn the textures into mixed shear components, which finally results in grain refinement and contributes to the high quality of the joint.

  17. Dynamics of fluid and light intensity in mechanically stirred photobioreactor.

    PubMed

    Zhang, T

    2013-10-10

    Turbulent flows in a single-stage and a two-stage impeller-stirred photobioreactor with a simple geometric configuration were analyzed using computational fluid dynamics. The trajectories of the microorganisms entrained in the flow field were traced by the particle tracking method. By projecting these trajectories onto a radial-axial (r-z) plane with a given azimuth angle, we were able to observe four different dynamics zones: circulation, pure rotation, trap, and slow-motion. Within the pure rotation zone, turbulence can be observed near the edges of the impeller. The light intensity and the light/dark cycles subjected by the microorganisms differ significantly in these zones. These differences can be further changed by providing different incident light illuminations on the reactor surface. The dynamics zones can be altered by modifying the geometric configuration of the reactor and the impeller stirring mechanism. In combination with the utilization of different incident light illuminations, the light intensity dynamics and the light/dark cycles subjected by the microorganisms can be controlled such that an optimal photobioreactor design with a high efficiency of light utilization and a high formation rate of the biochemical products can be realized.

  18. Microstructural Characterizations with EDAX Analysis of Dissimilar Friction Stir Welds

    NASA Astrophysics Data System (ADS)

    Ravikumar, S.; Rao, V. S.

    2013-10-01

    This paper reports the microstructural characteristics of dissimilar friction stir welds with AA7075T651 and AA6061T651. Dissimilar friction stir welds between AA7075T651 and AA6061T651 were produced by varying the rotational speeds between 800 and 1,000 rpm and the welding speeds between 90 and 110 mm/min. The welds were characterized through optical microscope and scanning electron microscope (SEM). Three different tool profiles (taper cylindrical threaded, taper square threaded and simple square) were used for this investigation and in that taper cylindrical threaded tool with process parameters 900 rpm and 100 mm/min were found to have maximum tensile strength of 205 MPa for the dissimilar butt joints. The SEM with energy-dispersive X-ray spectroscopy analysis reveals the metallurgical bonding achieved at the joint interfaces of the welds produced. The good mixing of both the materials joined was obtained at lower welding and higher rotational speed while the tunnel defect was found to be common in the welds produced irrespective of the tool pin profiles and process parameters due to insufficient axial load with 0° tilt angle.

  19. JOINING DISSIMILAR MATERIALS USING FRICTION STIR SCRIBE TECHNIQUE

    SciTech Connect

    Upadhyay, Piyush; Hovanski, Yuri; Jana, Saumyadeep; Fifield, Leonard S.

    2016-09-01

    Development of robust and cost effective method of joining dissimilar materials can provide a critical pathway to enable widespread use of multi-material design and components in mainstream industrial applications. The use of multi-material components such as Steel-Aluminum, Aluminum-Polymer allows design engineers to optimize material utilization based on service requirements and often lead weight and cost reductions. However producing an effective joint between materials with vastly different thermal, microstructural and deformation response is highly problematic using conventional joining and /or fastening methods. This is especially challenging in cost sensitive high volume markets that largely rely on low–cost joining solutions. Friction Stir Scribe technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like Magnesium and Aluminum to high temperature materials like Steels and Titanium. Additionally viable joints between polymer composites and metal can also be made using this method. This paper will present state of the art, progress made and challenges associated with this innovative derivative of Friction Stir welding in reference to joining dissimilar metals and polymer/metal combinations.

  20. Joining Dissimilar Materials Using Friction Stir Scribe Technique

    SciTech Connect

    Upadhyay, Piyush; Hovanski, Yuri; Jana, Saumyadeep; Fifield, Leonard S.

    2016-10-03

    Development of a robust and cost-effective method of joining dissimilar materials could provide a critical pathway to enable widespread use of multi-material designs and components in mainstream industrial applications. The use of multi-material components such as steel-aluminum and aluminum-polymer would allow design engineers to optimize material utilization based on service requirements and could often lead to weight and cost reductions. However, producing an effective joint between materials with vastly different thermal, microstructural, and deformation responses is highly problematic using conventional joining and/or fastening methods. This is especially challenging in cost sensitive, high volume markets that largely rely on low cost joining solutions. Friction stir scribe technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like magnesium and aluminum to high temperature materials like steel and titanium. Viable joints between polymer composites and metal can also be made using this method. This paper will present the state of the art, progress made, and challenges associated with this innovative derivative of friction stir welding in reference to joining dissimilar metals and polymer/metal combinations.

  1. Aeration costs in stirred-tank and bubble column bioreactors

    DOE PAGES

    Humbird, D.; Davis, R.; McMillan, J. D.

    2017-08-10

    To overcome knowledge gaps in the economics of large-scale aeration for production of commodity products, Aspen Plus is used to simulate steady-state oxygen delivery in both stirred-tank and bubble column bioreactors, using published engineering correlations for oxygen mass transfer as a function of aeration rate and power input, coupled with new equipment cost estimates developed in Aspen Capital Cost Estimator and validated against vendor quotations. Here, these simulations describe the cost efficiency of oxygen delivery as a function of oxygen uptake rate and vessel size, and show that capital and operating costs for oxygen delivery drop considerably moving from standard-sizemore » (200 m3) to world-class size (500 m3) reactors, but only marginally in further scaling up to hypothetically large (1000 m3) reactors. Finally, this analysis suggests bubble-column reactor systems can reduce overall costs for oxygen delivery by 10-20% relative to stirred tanks at low to moderate oxygen transfer rates up to 150 mmol/L-h.« less

  2. Metal Cutting Theory and Friction Stir Welding Tool Design

    NASA Technical Reports Server (NTRS)

    Payton, Lewis N.

    2003-01-01

    Friction Stir Welding (FSW) is a relatively new industrial process that was invented at The Weld Institute (TWI, United Kingdom) and patented in 1992 under research funded by in part by the National Aeronautics and Space Administration (NASA). Often quoted advantages of the process include good strength and ductility along with minimization of residual stress and distortion. Less well advertised are the beneficial effects of this solid state welding process in the field of occupational and environmental safety. It produces superior weld products in difficult to weld materials without producing any toxic fumes or solid waste that must be controlled as hazardous waste. In fact, it reduces noise pollution in the workspace as well. In the early days of FSW, most welding was performed on modified machine tools, in particular on milling machines with modified milling cutters. In spite of the obvious milling heritage of the process, the techniques and lessons learned from almost 250 years of successful metalworking with milling machines have not been applied in the field of modern Friction Stir Welding. The goal of the current research was to study currently successful FSW tools and parameterize the process in such a way that the design of new tools for new materials could be accelerated. Along the way, several successful new tooling designs were developed for current issues at the Marshall Space Flight Center with accompanying patent disclosures

  3. A model of material flow during friction stir welding

    SciTech Connect

    Hamilton, Carter Dymek, Stanislaw; Blicharski, Marek

    2008-09-15

    Tin plated 6061-T6 aluminum extrusions were friction stir welded in a 90 deg. butt-weld configuration. A banded microstructure of interleaved layers of particle-rich and particle-poor material comprised the weld nugget. Scanning and transmission electron microscopy revealed the strong presence of tin within the particle-rich bands, but TEM foils taken from the TMAZ, HAZ and base material showed no indication of Sn-containing phases. Since tin is limited to the surface of the pre-weld extrusions, surface material flowed into the nugget region, forming the particle-rich bands. Similarly, the particle-poor bands with no tin originated from within the thickness of the extrusions. A model of material flow during friction stir welding is proposed for which the weld nugget forms as surface material extrudes from the retreating side into a plasticized zone surrounding the FSW pin. The extruded column buckles between the extrusion force driving the material into the zone and the drag force of the in-situ material resisting its entry. A banded microstructure of interleaved surface material and in-situ material, therefore, develops. The model successfully describes several of the experimentally observed weld characteristics, but the model is limited to specific conditions of material flow and assumptions regarding steady-state.

  4. Parametric study of the Incompletely Stirred Reactor modeling

    SciTech Connect

    Mobini, K.; Bilger, R.W.

    2009-09-15

    The Incompletely Stirred Reactor (ISR) is a generalization of the widely-used Perfectly Stirred Reactor (PSR) model and allows for incomplete mixing within the reactor. Its formulation is based on the Conditional Moment Closure (CMC) method. This model is applicable to nonpremixed combustion with strong recirculation such as in a gas turbine combustor primary zone. The model uses the simplifying assumptions that the conditionally-averaged reactive-scalar concentrations are independent of position in the reactor: this results in ordinary differential equations in mixture fraction space. The simplicity of the model permits the use of very complex chemical mechanisms. The effects of the detailed chemistry can be found while still including the effects of micromixing. A parametric study is performed here on an ISR for combustion of methane at overall stoichiometric conditions to investigate the sensitivity of the model to different parameters. The focus here is on emissions of nitric oxide and carbon monoxide. It is shown that the most important parameters in the ISR model are reactor residence time, the chemical mechanism and the core-averaged Probability Density Function (PDF). Using several different shapes for the core-averaged PDF, it is shown that use of a bimodal PDF with a low minimum at stoichiometric mixture fraction and a large variance leads to lower nitric oxide formation. The 'rich-plus-lean' mixing or staged combustion strategy for combustion is thus supported. (author)

  5. Friction Stir Weld Restart+Reweld Repair Allowables

    NASA Technical Reports Server (NTRS)

    Clifton, Andrew

    2008-01-01

    A friction stir weld (FSW) repair method has been developed and successfully implemented on Al 2195 plate material for the Space Shuttle External Fuel Tank (ET). The method includes restarting the friction stir weld in the termination hole of the original weld followed by two reweld passes. Room temperature and cryogenic temperature mechanical properties exceeded minimum FSW design strength and compared well with the development data. Simulated service test results also compared closely to historical data for initial FSW, confirming no change to the critical flaw size or inspection requirements for the repaired weld. Testing of VPPA fusion/FSW intersection weld specimens exhibited acceptable strength and exceeded the minimum design value. Porosity, when present at the intersection was on the root side toe of the fusion weld, the "worst case" being 0.7 inch long. While such porosity may be removed by sanding, this "worst case" porosity condition was tested "as is" and demonstrated that porosity did not negatively affect the strength of the intersection weld. Large, 15-inch "wide panels" FSW repair welds were tested to demonstrate strength and evaluate residual stresses using photo stress analysis. All results exceeded design minimums, and photo stress analysis showed no significant stress gradients due to the presence of the restart and multi-pass FSW repair weld.

  6. Fatigue Performance of Friction-Stir-Welded Al-Mg-Sc Alloy

    NASA Astrophysics Data System (ADS)

    Zhemchuzhnikova, Daria; Mironov, Sergey; Kaibyshev, Rustam

    2017-01-01

    Fatigue behavior of a friction-stir-welded Al-Mg-Sc alloy was examined in cast and hot-rolled conditions. In both cases, the joints failed in the base material region and therefore the joint efficiency was 100 pct. The specimens machined entirely from the stir zone demonstrated fatigue strength superior to that of the base material in both preprocessed tempers. It was shown that the excellent fatigue performance of friction-stir joints was attributable to the ultra-fine-grained microstructure, the low dislocation density evolved in the stir zone, and the preservation of Al3Sc coherent dispersoids during welding. The formation of such structure hinders the initiation and growth of fatigue microcracks that provides superior fatigue performance of friction-stir welds.

  7. The Effect of Premixed Al-Cu Powder on the Stir Zone in Friction Stir Welding of AA3003-H18

    NASA Astrophysics Data System (ADS)

    Abnar, B.; Kazeminezhad, M.; Kokabi, A. H.

    2015-02-01

    In this research, 3-mm-thick AA3003-H18 non-heat-treatable aluminum alloy plates were joined by friction stir welding (FSW). It was performed by adding pure Cu and premixed Cu-Al powders at various rotational speeds of 800, 1000, and 1200 rpm and constant traveling speeds of 100 mm/min. At first, the powder was filled into the gap (0.2 or 0.4 mm) between two aluminum alloy plates, and then the FSW process was performed in two passes. The microstructure, mechanical properties, and formation of intermetallic compounds were investigated in both cases of using pure Cu and premixed Al-Cu powders. The results of using pure Cu and premixed Al-Cu powders were compared in the stir zone at various rotational speeds. The copper particle distribution and formation of Al-Cu intermetallic compounds (Al2Cu and AlCu) in the stir zone were desirable using premixed Al-Cu powder into the gap. The hardness values were significantly increased by formation of Al-Cu intermetallic compounds in the stir zone and it was uniform throughout the stir zone when premixed Al-Cu powder was used. Also, longitudinal tensile strength from the stir zone was higher when premixed Al-Cu powder was used instead of pure Cu powder.

  8. In-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction and silylation prior gas chromatography-mass spectrometry for ultraviolet filters determination in environmental water samples.

    PubMed

    Clavijo, Sabrina; Avivar, Jessica; Suárez, Ruth; Cerdà, Víctor

    2016-04-22

    A novel online approach involving in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction and derivatization coupled to gas chromatography-mass spectrometry has been developed for the determination of seven UV filters extensively used in cosmetic products in environmental water samples. The effect of parameters such as the type and volume of extraction solvent, dispersive solvent and derivatization agent, pH, ionic strength and stirring time, was studied using multivariate experimental design. Extraction, derivatization and preconcentration were simultaneously performed using acetone as dispersive solvent, N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as derivatization agent and trichloroethylene as extraction solvent. After stirring during 160s, the sedimented phase was transferred to a rotary micro-volume injection valve (3 μL) and introduced by an air stream into the injector of the GC through a stainless-steel tube used as interface. The detection limits were in the range of 0.023-0.16 μg L(-1) and good linearity was observed up to 500 μg L(-1) of the studied UV filters, with R(2) ranging between 0.9829 and 0.9963. The inter-day precision expressed as relative standard deviation (n=5) varied between 5.5 and 16.8%. Finally, the developed method was satisfactorily applied to assess the occurrence of the studied UV filters in seawater and pool water samples. Some of the studied UV filters were found in these samples and an add-recovery test was also successfully performed with recoveries between 82 and 111%. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. SLI Complex Curvature Friction Stir Weld Risk Reduction Program

    NASA Technical Reports Server (NTRS)

    Hartley, Paula J.; Schneider, Jules; Jones, Chip; Lawless, Kirby; Russell, Carolyn

    2003-01-01

    The Space Launch Initiative Program (SLI) in conjunction with the National Center for Advanced Manufacturing (NCAM) will demonstrate the ability to produce large-scale complex curvature hardware using the self-reacting friction stir welding process. This multi-phased risk reduction program includes friction stir welding process development and manufacture of a 22-ft diameter quarter dome using a conventional tooling approach; it culminates in a 27.5-ft diameter quarter dome demonstration performed on a 5-axis Universal Weld System. The design, fabrication, and installation of the Universal Weld System is made possible through a collaboration between the State of Louisiana, NASA, and the University of New Orleans. The Universal Weld System, manufactured by MTS Systems Corporation, will be installed at the Michoud Assembly Facility in New Orleans, Louisiana, and will be capable of manufacturing domes up to 30 ft in diameter. All welding will be accomplished using the Adaptable Adjustable Pin Tool (AdAPT) weld head and controller manufactured by MTS. Weld parameters will be developed for an aluminum alloy in gauges ranging from 0.320 to 0.400 in. thick. Weld quality will be verified through radiography, mechanical property testing at ambient and LN2 temperatures, and metallurgical analysis. The AdAPT weld head will then be mounted on a 22-ft diameter dome tool, which will be modified to include a welding track and drive system for moving the AdAPT weld head along the weld joint. This tool will then be used to manufacture a 22-ft diameter dome of an aluminum alloy, with 0.320-in. constant thickness joints, consisting of three individual gore panels. Finally, the 27.5-ft diameter quarter dome will be welded on the Universal Weld System. The quarter dome will consist of three individual gore panels with weld lands tapering from 0.320 to 0.360 in. in thickness. With the demonstration of these welds, the ability to manufacture large diameter domes using the friction stir

  10. Tool for Two Types of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Carter, Robert

    2006-01-01

    A tool that would be useable in both conventional and self-reacting friction stir welding (FSW) has been proposed. The tool would embody both a prior tooling concept for self-reacting FSW and an auto-adjustable pin-tool (APT) capability developed previously as an augmentation for conventional FSW. Some definitions of terms are prerequisite to a meaningful description of the proposed tool. In conventional FSW, depicted in Figure 1, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a rotating pin that protrudes from the shoulder into the depth of the workpiece. The main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional FSW is augmented with an APT capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or force-control system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding (SR-FSW), there are two rotating shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft, back into the FSW machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. A tool for SRFSW embodying this concept was reported in "Mechanism for Self-Reacted Friction Stir Welding" (MFS-31914), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 53. In its outward appearance, the proposed tool (see Figure 2) would fit the above description of an SR

  11. Microstructural and superplastic characteristics of friction stir processed aluminum alloys

    NASA Astrophysics Data System (ADS)

    Charit, Indrajit

    Friction stir processing (FSP) is an adapted version of friction stir welding (FSW), which was invented at The Welding Institute (TWI), 1991. It is a promising solid state processing tool for microstructural modification at localized scale. Dynamic recrystallization occurs during FSP resulting in fine grained microstructure. The main goal of this research was to establish microstructure/superplasticity relationships in FSP aluminum alloys. Different aluminum alloys (5083 Al, 2024 Al, and Al-8.9Zn-2.6Mg-0.09Sc) were friction stir processed for investigating the effect of alloy chemistry on resulting superplasticity. Tool rotation rate and traverse speeds were controlled as the prime FSP parameters to produce different microstructures. In another study, lap joints of 7475 Al plates were also studied to explore the possibility of developing FSW/superplastic forming route. Microstructures were evaluated using optical, scanning and transmission electron microscopy, orientation imaging microscopy and differential scanning calorimetry. Mechanical properties were evaluated using tensile testing. FSP 2024 Al (3.9 mum grain size) exhibited an optimum ductility of 525% at a strain rate of 10-2 s-1 and 430°C. Grain boundary sliding mechanism was found to be the dominant mode of deformation in this alloy. In 5083 Al alloy, it was found that changing the process parameters, grain sizes in the range of 3.5--8.5 mum grain size could be obtained. Material processed with colder processing parameters showed a decrease in ductility due to microstructural instability, and followed solute drag dislocation glide mechanism. On the other hand, materials processed with hotter parameter combinations showed mode of deformation related to grain boundary sliding mechanism. FSP of as-cast Al-Zn-Mg-Sc alloy resulted in ultrafine grains (0.68 mum) with attractive combination of high strain rate and low temperature superplasticity. This also demonstrated that superplastic microstructures could be

  12. Friction Stir Spot Welding of 6061 Aluminum-to-Copper

    NASA Astrophysics Data System (ADS)

    Heideman, Robert J.

    Friction stir spot welding (FSSW) between 1.5mm thick 6061 Al on top and 1.5mm thick Cu at bottom was conducted. First, weld parameters and the weld macrostructure that were necessary to form good quality welds, as determined using lap shear weld strength, were identified. Tool rotation speed and tool pin length are key variables that control weld strength. To obtain high quality strong welds, a Cu ring extruded upward from the lower Cu sheet into the upper 6061 Al-sheet, which promoted bonding and interlocking between the sheets, and an Al-rich stir zone between Cu ring and weld keyhole were both necessary. Second, a technique where the tool remained in the sample after FSSW helped determine the material flow that takes place during high quality weld formation and the functions of the welding tool features. The tool threads cause 6061 Al from the upper sheet to move downward into the region near the threads. The tool shoulder causes a counter flow movement of 6061 Al that results in the formation of the Al-rich stir zone and also causes the upward extrusion of the lower Cu sheet. This technique also identified that a Cu-rich material forms on the tool tip, that this material sheds and rebuilds during subsequent welds, and that this material can form large Cu-rich particles that can completely fill the tool threads, impede proper material flow and lead to a low strength, poor quality weld. Third, to further understand welding parameters, weld temperatures, torque, and vertical forces were measured. Temperature data was collected using a tool holder that permitted wireless thermocouple data collection. Through these measurements, rotational plunge weld energy was recognized as important in determining if a quality weld formed, and weld plunge rate was identified as the welding parameter that significantly impacted rotational weld plunge energy. The final phase of research was to improve weld quality consistency. Through repetitive trials with a single tool

  13. Optimization based inversion method for the inverse heat conduction problems

    NASA Astrophysics Data System (ADS)

    Mu, Huaiping; Li, Jingtao; Wang, Xueyao; Liu, Shi

    2017-05-01

    Precise estimation of the thermal physical properties of materials, boundary conditions, heat flux distributions, heat sources and initial conditions is highly desired for real-world applications. The inverse heat conduction problem (IHCP) analysis method provides an alternative approach for acquiring such parameters. The effectiveness of the inversion algorithm plays an important role in practical applications of the IHCP method. Different from traditional inversion models, in this paper a new inversion model that simultaneously highlights the measurement errors and the inaccurate properties of the forward problem is proposed to improve the inversion accuracy and robustness. A generalized cost function is constructed to convert the original IHCP into an optimization problem. An iterative scheme that splits a complicated optimization problem into several simpler sub-problems and integrates the superiorities of the alternative optimization method and the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm is developed for solving the proposed cost function. Numerical experiment results validate the effectiveness of the proposed inversion method.

  14. Emission of volatile organic compounds and production of secondary organic aerosol from stir-frying spices.

    PubMed

    Liu, Tengyu; Liu, Qianyun; Li, Zijun; Huo, Lei; Chan, ManNin; Li, Xue; Zhou, Zhen; Chan, Chak K

    2017-12-01

    Cooking is an important source of volatile organic compounds (VOCs) and a potential source of secondary organic aerosol (SOA) both indoors and outdoors. In this study, VOC emissions from heating corn oil and stir-frying spices (i.e. garlic, ginger, myrcia and zanthoxylum piperitum (Sichuan pepper)) were characterized using an on-line membrane inlet vacuum ultraviolet single-photon ionization time-of-flight mass spectrometer (VUV-SPI-TOFMS). VOC emissions from heating corn oil were dominated by aldehydes, which were enhanced by factors of one order of magnitude when stir-frying spices. Stir-frying any of the spices studied generated large amounts of methylpyrrole (m/z 81). In addition, stir-frying garlic produced abundant dihydrohydroxymaltol (m/z 144) and diallyldisulfide (DADS) (m/z 146), while stir-frying ginger, myrcia and zanthoxylum piperitum produced abundant monoterpenes (m/z 136) and terpenoids (m/z 152, 154). SOA formed from emissions of stir-frying spices through reactions with excess ozone in a flow reactor as well as primary organic aerosol (POA) emissions were characterized using a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS). Stir-frying garlic and ginger generated similar POA concentrations to those from heating corn oil while stir-frying myrcia and zanthoxylum piperitum generated double the amount of emissions. No SOA was observed from stir-frying garlic and ginger. The rates of SOA production from stir-frying myrcia and zanthoxylum piperitum were 1.8μgmin(-1)gspice(-1) and 8.7μgmin(-1)gspice(-1), equivalent to 13.4% and 53.1% of their own POA emission rates, respectively. Therefore, the contribution of stir-frying spices to ambient organic aerosol levels is likely dominated by POA. The rates of total terpene emission from stir-frying myrcia and zanthoxylum piperitum were estimated to be 5.1μgmin(-1)gspice(-1) and 24.9μgmin(-1)gspice(-1), respectively. Our results suggest

  15. Multiresolution MR elastography using nonlinear inversion

    PubMed Central

    McGarry, M. D. J.; Van Houten, E. E. W.; Johnson, C. L.; Georgiadis, J. G.; Sutton, B. P.; Weaver, J. B.; Paulsen, K. D.

    2012-01-01

    Purpose: Nonlinear inversion (NLI) in MR elastography requires discretization of the displacement field for a finite element (FE) solution of the “forward problem”, and discretization of the unknown mechanical property field for the iterative solution of the “inverse problem”. The resolution requirements for these two discretizations are different: the forward problem requires sufficient resolution of the displacement FE mesh to ensure convergence, whereas lowering the mechanical property resolution in the inverse problem stabilizes the mechanical property estimates in the presence of measurement noise. Previous NLI implementations use the same FE mesh to support the displacement and property fields, requiring a trade-off between the competing resolution requirements. Methods: This work implements and evaluates multiresolution FE meshes for NLI elastography, allowing independent discretizations of the displacements and each mechanical property parameter to be estimated. The displacement resolution can then be selected to ensure mesh convergence, and the resolution of the property meshes can be independently manipulated to control the stability of the inversion. Results: Phantom experiments indicate that eight nodes per wavelength (NPW) are sufficient for accurate mechanical property recovery, whereas mechanical property estimation from 50 Hz in vivo brain data stabilizes once the displacement resolution reaches 1.7 mm (approximately 19 NPW). Viscoelastic mechanical property estimates of in vivo brain tissue show that subsampling the loss modulus while holding the storage modulus resolution constant does not substantially alter the storage modulus images. Controlling the ratio of the number of measurements to unknown mechanical properties by subsampling the mechanical property distributions (relative to the data resolution) improves the repeatability of the property estimates, at a cost of modestly decreased spatial resolution. Conclusions: Multiresolution

  16. A passive inverse filter for Green's function retrieval.

    PubMed

    Gallot, Thomas; Catheline, Stefan; Roux, Philippe; Campillo, Michel

    2012-01-01

    Passive methods for the recovery of Green's functions from ambient noise require strong hypotheses, including isotropic distribution of the noise sources. Very often, this distribution is nonisotropic, which introduces bias in the Green's function reconstruction. To minimize this bias, a spatiotemporal inverse filter is proposed. The method is tested on a directive noise field computed from an experimental active seismic data set. The results indicate that the passive inverse filter allows the manipulation of the spatiotemporal degrees of freedom of a complex wave field, and it can efficiently compensate for the noise wavefield directivity.

  17. Determination of off-flavor compounds, 2-methylisoborneol and geosmin, in salmon fillets using stir bar sorptive extraction-thermal desorption coupled with gas chromatography-mass spectrometry.

    PubMed

    Ruan, E D; Aalhus, J L; Summerfelt, S T; Davidson, J; Swift, B; Juárez, M

    2013-12-20

    A sensitive and solvent-less method for the determination of musty and earthy off-flavor compounds, 2-methylisoborneol (MIB) and geosmin (GSM), in salmon tissue was developed using stir bar sorptive extraction-thermal desorption coupled with gas chromatography-mass spectrometry (SBSE-TD-GCMS). MIB and GSM were solid phase extracted using polydimethylsiloxane (PDMS) coated stir bars, analyzed by gas chromatography, and detected in full scan mode of mass selective detector (MSD). Using this method, the calibration curves of MIB and GSM were linear in the range of 0.3-100ng/L, with a correlation coefficient above 0.999 and RSDs less than 4% (n=4). The limit of detection (LOD, S/N=3, n=6) and limit of quantification (LOQ, S/N=10, n=6) of MIB and GSM were both ∼0.3 and 1ng/L, respectively. The recoveries of MIB and GSM were 22% and 29% by spike in 30ng/L standard compounds, 23% and 30% by spike-in 100ng/L standard compounds in salmon tissue samples with good precision (<8% of RSDs, n=6), respectively. The recoveries of MIB and GSM were better than reported methodologies using SPME fibres (<10%) in fish tissue samples. This method was successfully applied to monitor and characterize depurated salmon fillet samples (0, 3, 6 and 10 days).

  18. Determination of synthetic phenolic antioxidants in soft drinks by stir-bar sorptive extraction coupled to gas chromatography-mass spectrometry.

    PubMed

    Cacho, Juan Ignacio; Campillo, Natalia; Viñas, Pilar; Hernández-Córdoba, Manuel

    2015-01-01

    The synthetic phenolic antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butyl hydroquinone (TBHQ) were pre-concentrated by stir-bar sorptive extraction and thermally desorbed (SBSE-TD) before analysis by GC-MS. Several parameters affecting the derivatisation step and both SBSE extraction and thermal desorption were carefully optimised. When the analyses of BHA and TBHQ in their acetylated, silylated and underivatised forms were compared, the best results were obtained when the in-situ derivatisation procedure with acetic anhydride was employed. Quantification was carried out using carvacrol as the internal standard, providing quantification limits of between 0.11 and 0.15 ng ml(-1), depending on the compound. Recovery assays for samples spiked at two concentration levels, 1 and 5 ng ml(-1), provided recoveries in the 81-117% range. The proposed method was applied in the analysis canned soft drinks and the analytes were found in five of the 10 samples analysed.

  19. Friction Stir Welding of ODS and RAFM Steels

    SciTech Connect

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; Tan, Lizhen; Sokolov, Mikhail A.

    2015-09-14

    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this paper, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW on grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Finally, post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.

  20. Lateral position detection and control for friction stir systems

    DOEpatents

    Fleming, Paul [Boulder, CO; Lammlein, David H [Houston, TX; Cook, George E [Brentwood, TN; Wilkes, Don Mitchell [Nashville, TN; Strauss, Alvin M [Nashville, TN; Delapp, David R [Ashland City, TN; Hartman, Daniel A [Fairhope, AL

    2011-11-08

    Friction stir methods are disclosed for processing at least one workpiece using a rotary tool with rotating member for contacting and processing the workpiece. The methods include oscillating the rotary tool laterally with respect to a selected propagation path for the rotating member with respect to the workpiece to define an oscillation path for the rotating member. The methods further include obtaining force signals or parameters related to the force experienced by the rotary tool at least while the rotating member is disposed at the extremes of the oscillation. The force signals or parameters associated with the extremes can then be analyzed to determine a lateral position of the selected path with respect to a target path and a lateral offset value can be determined based on the lateral position. The lateral distance between the selected path and the target path can be decreased based on the lateral offset value.

  1. Material Flow during Friction Stir Welding of HSLA 65 Steel

    NASA Astrophysics Data System (ADS)

    Young, John; Field, David; Nelson, Tracy

    2013-07-01

    Material flow during friction stir welding of HSLA-65 steel was investigated by crystallographic texture analysis. During the welding process, the steel deforms primarily by local shear deformation in the austenite phase and then transforms upon cooling. Texture data from three weld specimens were compared to theoretical textures calculated using ideal Euler angles for shear in face centered cubic (FCC) structures transformed by the Kurdjumov-Sacks (KS) relationship. These theoretical textures show similarities to the experimental textures. Texture data from the weld specimens revealed a rotation of the shear direction corresponding to the tangent of the weld tool on both the area directly under the weld tool shoulder and weld cross sections. In addition, texture data showed that while the shear plane of the area under the weld tool shoulder remained constant, the shear plane of the weld cross sections is influenced by the weld tool pin.

  2. Pin Tool Geometry Effects in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Querin, J. A.; Rubisoff, H. A.; Schneider, J. A.

    2009-01-01

    In friction stir welding (FSW) there is significant evidence that material can take one of two different flow paths when being displaced from its original position in front of the pin tool to its final position in the wake of the weld. The geometry of the pin tool, along with the process parameters, plays an important role in dictating the path that the material takes. Each flow path will impart a different thermomechanical history on the material, consequently altering the material microstructure and subsequent weld properties. The intention of this research is to isolate the effect that different pin tool attributes have on the flow paths imparted on the FSWed material. Based on published weld tool geometries, a variety of weld tools were fabricated and used to join AA2219. Results from the tensile properties and microstructural characterization will be presented.

  3. Grain size reduction by electromagnetic stirring inside gold alloys

    NASA Astrophysics Data System (ADS)

    Ernst, R.; Mangelinck-Noël, N.; Hamburger, J.; Garnier, C.; Ramoni, P.

    2005-06-01

    The final properties of cast materials depend greatly on the solidification process undergone by the material. In this paper, we study gold alloys dedicated to the watch industry and jewellery in the framework of a research collaboration with the Metalor Company. The aim is to improve the concentration homogeneity of the ingots by controlling the solidification step. It can be achieved by reducing segregations by a decrease in the grain size. For this purpose, we set up a multiphase electromagnetic stirring of the melt to favour the growth of finer grains and improve the homogeneity of the composition. We first design an electromagnetic stirrer by numerical simulation. The stirrer is then implemented on a model experiment. Eventually, the alloys are characterised by metallography and etching to evidence the grain structure. As expected, we obtain a substantial reduction of the grain size although, some work remains to be done to attain the final goal of even finer grains.

  4. Friction Stir Welding of ODS and RAFM Steels

    DOE PAGES

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; ...

    2015-09-14

    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this paper, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW onmore » grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Finally, post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.« less

  5. Tidal stirring and phytoplankton bloom dynamics in an estuary

    USGS Publications Warehouse

    Cloern, J.E.

    1991-01-01

    In South San Francisco Bay, estuarine phytoplankton biomass fluctuates at the time scale of days to weeks; much of this variability is associated with fluctuations in tidal energy. During the spring seasons of every year from 1980-1990, episodic blooms occurred in which phytoplankton biomass rose from a baseline of 2-4mg chlorophyll a m-3, peaked at 20-40 chlorophyll a m-3, then returned to baseline values, all within several weeks. Each episode of biomass increase occurred during neap tides, and each bloom decline coincided with spring tides. This suggests that daily variations in the rate of vertical mixing by tidal stirring might control phytoplankton bloom dynamics in some estuaries. Simulation experiments with a numerical model of phytoplankton population dynamics support this hypothesis. -from Author

  6. FRICTION-STIR-LAP-WELDS OF AA6111 ALUMINUM ALLOY

    SciTech Connect

    Yadava, Manasij; Mishra, Rajiv S.; Chen, Y. L.; Gayden, X.; Grant, Glenn J.

    2007-01-09

    Lap joints of 1 mm thick AA6111 aluminum sheets were made by friction stir welding, using robotic and conventional machines. Welds were made for advancing as well as retreating side loading. Thinning in welds was quantified. Lap shear test of welds was conducted in as-welded and paint-baked conditions. Conventional machine welds showed less thinning and better strength than robotic machine welds. Process forces in conventional machine welding were higher. Paint bake treatment improved the weld strength; but the improvement varied with process parameters. Advancing side loaded welds achieved higher strength than the retreating side loaded welds. Fracture location was found to occur on the loaded side of the weld and along the thinning defect.

  7. New insights on oxygen absorption in unsparged stirred vessels

    NASA Astrophysics Data System (ADS)

    Averkina, A. S.; Kazakov, D. A.; Asnin, L. D.; Kaczmarski, K.; Krol, G.; Vol'khin, V. V.

    2016-12-01

    A combination of experimental and numerical techniques revealed subtle features of oxygen absorption in unsparged stirred vessels. It was shown that the absorption kinetics was influenced not only by the mass transfer resistance in the gas-liquid interface but also by imperfect mixing in the bulk liquid. The liquid's viscosity and density were suggested to affect the oxygen mass transfer by influencing the turbulence both at the surface and in the bulk phase, while the modification of the surface layer through surfactant addition affected only surface turbulence. The axial dispersion model proved good in the explanation of the experimental results. For the sake of comparison, the classical stagnant film model was also tested but led to slight, yet systematic, deviations in its predictions from the experimental data.

  8. Stirring with ghost rods in a lid-driven cavity

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Chen, Jie; Stremler, Mark

    2009-11-01

    It has shown that passive fluid particles moving on periodic orbits can be used to `stir' a viscous fluid in a two-dimensional lid-driven cavity that exhibits a figure-eight flow pattern (Stremler & Chen 2007). Fluid motion in the vicinity of these particles produces ``ghost rod'' structures that behave like semi-permeable rods in the flow. Since these ghost rods are present due to the system dynamics, perturbations in the boundary conditions lead to variations in the existence and structure of the ghost rods. We discuss these variations and assess the role of ghost rods in mixing over a range of operating conditions for this system. The results suggest that ghost rods can play an important role in mixing for other counter-rotating flows.

  9. Application of stir bar sorptive extraction for wine analysis.

    PubMed

    Hayasaka, Yoji; MacNamara, Kevin; Baldock, Gayle A; Taylor, Randell L; Pollnitz, Alan P

    2003-04-01

    Stir bar sorptive extraction (SBSE) coupled with gas chromatography/mass spectrometry (GC/MS) was used to analyse wine samples for three applications: flavour and compositional analysis; 2,4,6-trichloroanisole (TCA), a common off-aroma in wine; and agrochemicals. SBSE was found to be orders of magnitude more sensitive than modern conventional methodology, allowing for lower detection and quantitation levels, and improved confirmation of identity; SBSE often gave better signal to noise in scan mode than other methods in selective ion monitoring (SIM) mode. With the help of their characteristic mass spectra all agrochemicals could be identified unambiguously at concentrations of 10 microg L(-1) in wine and a further 100 constituents were detected in a Cabernet Sauvignon sample. Thus it is now possible to analyse complex samples such as wine by scan mode, with better confirmation of identity, and without sacrificing sensitivity, where previously SIM methodology had to be used.

  10. Lap Joints of 6061 Al Alloys by Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Tashkandi, M. A.

    2017-06-01

    Lap joints of 6061 aluminium alloys were obtained using friction stir welding. The welding parameters used are: rotational speed, welding speed and pin Length. There were two levels of each factor involved. Rotational speed levels were 900 and 1120 rpm, welding speed levels were 1 and 1.5 mm/sec and pin length levels were 4.5 and 5.5 mm. Successful lap joints were produced for the different combinations of the above welding parameters. The joints quality tested under tensile testing and the microstructure of the welding zone were studied. Fracture mostly occurred in the base metal for most lap-shear welded joints. The exception was joints with welding parameters as follows: rotational speed 900 rpm, the welding speed 1.5 mm/sec and pin length 4.5 mm. In this case, the fracture occurred in the welding zone.

  11. Joining dissimilar materials using Friction Stir scribe technique

    SciTech Connect

    Upadhyay, Piyush; Hovanski, Yuri; Jana, Saumyadeep; Fifield, Leonard S.

    2016-10-03

    The ability to effectively join materials with vastly different melting points like Aluminum-Steel, Polymer composites - metals has been one of the road blocks in realizing multi-material components for light weighting efforts. Friction stir scribe (FSS) technique is a promising method that produces continuous overlap joint between materials with vastly different melting regimes and high temperature flow characteristics. FSS uses an offset cutting tool at the tip of the FSW pin to create an insitu mechanical interlock between material interfaces. With investments from Vehicle Technology office, US DOE and several automotive manufacturers and suppliers PNNL is developing the FSS process and has demonstrated viability of joining several material combinations. Details of welding trails, unique challenges and mitigation strategies in different material combinations will be discussed. Joint characterization including mechanical tests and joint performances will also be presented.

  12. Metal cutting analogy for establishing Friction Stir Welding process parameters

    NASA Astrophysics Data System (ADS)

    Stafford, Sylvester Allen

    A friction stir weld (FSW) is a solid state joining operation whose processing parameters are currently determined by lengthy trial and error methods. To implement FSWing rapidly in various applications will require an approach for predicting process parameters based on the physics of the process. Based on hot working conditions for metals, a kinematic model has been proposed for calculating the shear strain and shear strain rates during the FSW process, validation of the proposed model with direct measuring is difficult however. Since the shear strain and shear strain rates predicted for the FSW process, are similar to those predicted in metal cutting, validation of the FSW algorithms with microstructural studies of metal chips may be possible leading to the ability to predict FSW processing parameters.

  13. Friction Stir Welding of ODS and RAFM Steels

    NASA Astrophysics Data System (ADS)

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; Tan, Lizhen; Sokolov, Mikhail A.

    2015-09-01

    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this work, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW on grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.

  14. A cubic autocatalytic reaction in a continuous stirred tank reactor

    SciTech Connect

    Yakubu, Aisha Aliyu; Yatim, Yazariah Mohd

    2015-10-22

    In the present study, the dynamics of the cubic autocatalytic reaction model in a continuous stirred tank reactor with linear autocatalyst decay is studied. This model describes the behavior of two chemicals (reactant and autocatalyst) flowing into the tank reactor. The behavior of the model is studied analytically and numerically. The steady state solutions are obtained for two cases, i.e. with the presence of an autocatalyst and its absence in the inflow. In the case with an autocatalyst, the model has a stable steady state. While in the case without an autocatalyst, the model exhibits three steady states, where one of the steady state is stable, the second is a saddle point while the last is spiral node. The last steady state losses stability through Hopf bifurcation and the location is determined. The physical interpretations of the results are also presented.

  15. Prolegomena to the Study of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2010-01-01

    The literature contains many approaches toward modeling of the friction stir welding (FSW) process with varying treatments of the weld metal properties. It is worthwhile to consider certain fundamental features of the process before attempting to interpret FSW phenomena: Because of the unique character of metal deformation (as opposed to, say, viscous deformation) a velocity "discontinuity" or shear surface occurs in FSW and determines much of the character of the welding mechanism. A shear surface may not always produce a sound bond. Balancing mechanical power input against conduction and convection heat losses yields a relation, a "temperature index", between spindle speed and travel speed to maintain constant weld temperature. But many process features are only weakly dependent upon temperature. Thus, unlike modeling of metal forming processes, it may be that modeling the FSW process independently of the material conditions has some merit.

  16. Stir bar sorptive extraction: recent applications, limitations and future trends.

    PubMed

    Camino-Sánchez, F J; Rodríguez-Gómez, R; Zafra-Gómez, A; Santos-Fandila, A; Vílchez, J L

    2014-12-01

    Stir bar sorptive extraction (SBSE) has generated growing interest due to its high effectiveness for the extraction of non-polar and medium-polarity compounds from liquid samples or liquid extracts. In particular, in recent years, a large amount of new analytical applications of SBSE has been proposed for the extraction of natural compounds, pollutants and other organic compounds in foods, biological samples, environmental matrices and pharmaceutical products. The present review summarizes and discusses the theory behind SBSE and the most recent developments concerning its effectiveness. In addition, the main results of recent analytical approaches and their applications, published in the last three years, are described. The advantages, limitations and disadvantages of SBSE are described and an overview of future trends and novel extraction sorbents and supports is given.

  17. Lunar petrogenesis in a well-stirred magma ocean

    NASA Technical Reports Server (NTRS)

    Wood, J. A.

    1975-01-01

    The principal group of low-KREEP highlands rocks as indicated by quartz-olivine-anorthite pseudoternary phase diagrams shows chemical trends which violate the Bowen reaction principle, in that the greater the concentration of magnesian and mafic minerals, the more sodic the coexisting plagioclase tends to be. It is suggested that this trend was established during the primary differentiation of the lunar crust and is a result of crystallization in a vigorously convecting (well-stirred) system. Under these conditions all plagioclase crystals, all pyroxene crystals, and all of the residual liquid remain fairly uniform in composition until advanced crystallization immobilizes the system. The rock suite then established would vary continuously from anorthositic types at the top to ultramafic types at the bottom.

  18. A cubic autocatalytic reaction in a continuous stirred tank reactor

    NASA Astrophysics Data System (ADS)

    Yakubu, Aisha Aliyu; Yatim, Yazariah Mohd

    2015-10-01

    In the present study, the dynamics of the cubic autocatalytic reaction model in a continuous stirred tank reactor with linear autocatalyst decay is studied. This model describes the behavior of two chemicals (reactant and autocatalyst) flowing into the tank reactor. The behavior of the model is studied analytically and numerically. The steady state solutions are obtained for two cases, i.e. with the presence of an autocatalyst and its absence in the inflow. In the case with an autocatalyst, the model has a stable steady state. While in the case without an autocatalyst, the model exhibits three steady states, where one of the steady state is stable, the second is a saddle point while the last is spiral node. The last steady state losses stability through Hopf bifurcation and the location is determined. The physical interpretations of the results are also presented.

  19. Inverse plasma equilibria

    SciTech Connect

    Hicks, H.R.; Dory, R.A.; Holmes, J.A.

    1983-01-01

    We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J/sub 0/(rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model.

  20. Asteroid lightcurve inversion

    NASA Technical Reports Server (NTRS)

    Ostro, Steven J.; Connelly, Robert

    1987-01-01

    One of the most fundamental physical properties of any asteroid is its shape. Lightcurves provide the only source of shape information for most asteroids. Unfortunately, the functional form of a lightcurve is determined by the viewing/illumination geometry and the asteroid's light scattering characteristics as well as its shape, and in general it is impossible to determine an asteroid's shape from lightcurves. A technique called convex-profile inversion (CPI) that obtains a convex profile, P, from any lightcurve is introduced. If certain ideal conditions are satisfied, then P is an estimator for the asteroid's mean cross section, C, a convex set defined as the average of all cross sections C(z) cut by planes a distance z above the asteroids's equatorial plane. C is therefore a 2-D average of the asteroid's 3-D shape.

  1. Inverse Compton for Compton

    NASA Astrophysics Data System (ADS)

    Suortti, Pekka

    2016-04-01

    A novel concept for a high resolution Compton spectrometer is introduced. 88 keV radiation from an Inverse Compton Compact Source is focused using crossed cylindrically bent Laue-type Si perfect crystals, and dispersed on the sample with a constant energy gradient. Dispersion is compensated exactly at a Ge crystal analyzer, so that the same wavelength shift is observed for all wavelengths of the incident beam. The ThomX source is used as a concrete example. Detailed dimensions and flux estimates at successive locations of the spectrometer are given, and the performance is compared with the dispersion compensating spectrometer at ID15 of the ESRF. The momentum resolution is better than 0.1 atomic units in both cases. The intensity of scattering with the compact source is an order of magnitude smaller, but still adequate for high resolution Compton profile measurements.

  2. Laser-Assisted Stir Welding of 25-mm-Thick HSLA-65 Plate

    NASA Astrophysics Data System (ADS)

    Williamson, Keith M.

    2002-12-01

    Laser-assisted stir welding is a hybrid process that combines energy from a laser with functional heating and mechanical energy to join materials in the solid state. The technology is an adaptation of friction stir welding which is particularly suited for joining thick plates. Aluminum plates up to 75 mm thick have been successfully joined using friction stir welding. Since joining occurs in the solid state, stir technology offers the capability for fabricating full penetration joints in thick plates with better mechanical properties and less weld distortion than is possible by fusion processes. Currently friction stir welding is being used in several industries to improve productivity, reduce weight, and increase the strength of welded structures. Examples include: (a) the aircraft/aerospace industry where stir technology is currently being used to fabricate the space shuttle's external tank as well as components of the Delta family of rockets; (b) the shipping industry where container manufacturers are using stir technology to produce lighter containers with more payload capacity; and (c) the oil industry where offshore platform manufactures are using automated stir welding plants to fabricate large panels and structures up to 16 meters long with widths as required. In all these cases, stir technology has been restricted to aluminum alloys; however, stainless and HSLA 65 steels have been recently stir welded with friction as the primary heat source. One of the difficulties in adapting stir welding to steel is tool wear aggravated by the high tool rubbing velocities needed to provide frictional heat input into the material. Early work showed that the tool shoulder reached temperatures above 1000 C and the weld seam behind the tool stayed within this temperature range for up to 25 mm behind the tool. Cross sections of stir welded samples showed that the heat-affected zone is relatively wide and follows the profile of the tool shoulder. Besides minimizing the tool

  3. Controlled polymerization of acrylonitrile proceeded along with the Belousov-Zhabotinsky oscillator by changing its stirring conditions

    NASA Astrophysics Data System (ADS)

    Furue, Yuuka; Okano, Kunihiko; Banno, Taisuke; Asakura, Kouichi

    2016-02-01

    Chemical oscillations of the manganese-ion catalyzed Belousov-Zhabotinsky (BZ) reaction system were found to be controlled by changing its stirring conditions. The oscillation stopped at a high stirring rate, while it reappeared immediately by reducing the stirring rate. It is known in the BZ reaction system, that the radical polymerization takes place along with the oscillation when acrylic monomers are added. By the addition of acrylonitrile to the system stirred at a high stirring rate, the oscillation as well as the polymerization of acrylonitrile stopped. The radical polymerization of acrylonitrile by the BZ oscillator is thus found to be made controllable by changing the mixing conditions.

  4. Versatile Friction Stir Welding/Friction Plug Welding System

    NASA Technical Reports Server (NTRS)

    Carter, Robert

    2006-01-01

    A proposed system of tooling, machinery, and control equipment would be capable of performing any of several friction stir welding (FSW) and friction plug welding (FPW) operations. These operations would include the following: Basic FSW; FSW with automated manipulation of the length of the pin tool in real time [the so-called auto-adjustable pin-tool (APT) capability]; Self-reacting FSW (SRFSW); SR-FSW with APT capability and/or real-time adjustment of the distance between the front and back shoulders; and Friction plug welding (FPW) [more specifically, friction push plug welding] or friction pull plug welding (FPPW) to close out the keyhole of, or to repair, an FSW or SR-FSW weld. Prior FSW and FPW systems have been capable of performing one or two of these operations, but none has thus far been capable of performing all of them. The proposed system would include a common tool that would have APT capability for both basic FSW and SR-FSW. Such a tool was described in Tool for Two Types of Friction Stir Welding (MFS- 31647-1), NASA Tech Briefs, Vol. 30, No. 10 (October 2006), page 70. Going beyond what was reported in the cited previous article, the common tool could be used in conjunction with a plug welding head to perform FPW or FPPW. Alternatively, the plug welding head could be integrated, along with the common tool, into a FSW head that would be capable of all of the aforementioned FSW and FPW operations. Any FSW or FPW operation could be performed under any combination of position and/or force control.

  5. EVOLUTIONARY TRACKS OF TIDALLY STIRRED DISKY DWARF GALAXIES

    SciTech Connect

    Lokas, Ewa L.; Kazantzidis, Stelios; Mayer, Lucio E-mail: stelios@mps.ohio-state.edu

    2011-09-20

    Using collisionless N-body simulations, we investigate the tidal evolution of late-type, rotationally supported dwarfs inside Milky Way sized host galaxies. Our study focuses on a wide variety of dwarf orbital configurations and initial structures. During the evolution, the disky dwarfs undergo strong mass loss, the stellar disks are transformed into spheroids, and rotation is replaced by random motions of the stars. Thus, the late-type progenitors are transformed into early-type dwarfs as envisioned by the tidal stirring model for the formation of dwarf spheroidal (dSph) galaxies in the Local Group. We determine the photometric properties of the dwarfs, including the total visual magnitude, the half-light radius, and the central surface brightness as they would be measured by an observer near the galactic center. Special emphasis is also placed on studying their kinematics and shapes. We demonstrate that the measured values are biased by a number of observational effects including the increasing angle of the observation cone near the orbital pericenter, the fact that away from the pericenter the tidal tails are typically oriented along the line of sight, and the fact that for most of the evolution the stellar components of the dwarfs are triaxial ellipsoids whose major axis tumbles with respect to the line of sight. Finally, we compare the measured properties of the simulated dwarfs to those of dwarf galaxies in the Local Group. The evolutionary tracks of the dwarfs in different parameter planes and the correlations between their different properties, especially the total magnitude and the surface brightness, strongly suggest that present-day dSph galaxies may have indeed formed from late-type progenitors as proposed by the tidal stirring scenario.

  6. Bulk viscosity of stirred xenon near the critical point

    NASA Astrophysics Data System (ADS)

    Gillis, K. A.; Shinder, I. I.; Moldover, M. R.

    2005-11-01

    We deduce the thermophysical properties of near-critical xenon from measurements of the frequencies and half-widths of the acoustic resonances of xenon maintained at its critical density in centimeter-sized cavities. In the reduced temperature range 1×10-3<(T-Tc)/Tc<7×10-6 , we measured the resonance frequency and quality factor (Q) for each of six modes spanning a factor of 27 in frequency. As Tc was approached, the frequencies decreased by a factor of 2.2 and the Q ’s decreased by as much as a factor of 140. Remarkably, these results are predicted (within ±2% of the frequency and within a factor of 1.4 of Q ) by a model for the resonator and a model for the frequency-dependent bulk viscosity ζ(ω) that uses no empirically determined parameters. The resonator model is based on a theory of acoustics in near-critical fluids developed by Gillis, Shinder, and Moldover [Phys. Rev. E 70, 021201 (2004)]. In addition to describing the present low-frequency data (from 120Hzto7.5kHz ), the model for ζ(ω) is consistent with ultrasonic (0.4-7MHz) velocity and attenuation data from the literature. However, the model predicts a peak in the temperature dependence of the dissipation in the boundary layer that we did not detect. This suggests that the model overestimates the effect of the bulk viscosity on the thermal boundary layer. In this work, the acoustic cavities were heated from below to stir the xenon, thereby reducing the density stratification resulting from Earth’s gravity. The stirring reduced the apparent equilibration time from several hours to a few minutes, and it reduced the effective temperature resolution from 60mK to approximately 2mK , which corresponds to (T-Tc)/Tc≈7×10-6 .

  7. Investigation of Machine Design for Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Romine, Peter L.

    1996-01-01

    The process of joining two pieces of metal together has not significantly changed over the last few decades. The basic idea used is to bring the pieces together and apply enough heat to melt the metal at the interface. The molten metal mixes and after cooling forms a strong joint. This process is called the fusion process. The most significant difference between the many fusion processes is how the heat is generated and applied. The Welding Institute (TWI), in Great Britain, has recently patented an innovative application of mechanical friction. TWI designed a tool and process called Friction Stir Welding (FSW) that uses friction to heat the metal to within a few hundred degrees Fahrenheit of melting, just to the point of being plastic-like. The tool then stirs the plasticized metal together forming a joint that has been shown to be as good or better than an equivalent fusion joint. The FSW process is well suited for the joining of the aluminum alloys used in the aerospace industry. The relatively low melting point of aluminum eliminates the requirements for exotic materials for pin tool design. The FSW process has been successfully used to join alloys such as 7075 which were before considered "unweldable", and aluminum-lithium 2195 which exhibits many problems when fusion welded. The objective this summer was to investigate the design of a FSW system that could take this process from the laboratory to the manufacturing floor. In particular, it was the goal of my NASA colleague to develop a concept for applying the FSW process to the manufacturing of aluminum cryogenic oxygen and hydrogen tanks, of the sort used to make the Shuttle External Tank.

  8. Auto-adjustable pin tool for friction stir welding

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor); Oelgoetz, Peter A. (Inventor)

    1999-01-01

    An auto-adjusting pin tool for friction stir welding is presented wherein the pin tool automatically adjusts for welding materials of varying thicknesses, and the pin can be incrementally withdrawn from the workpieces thus eliminating any crater or keyhole in the weld. The inventive apparatus is comprised of a welding head housing a motor connected to a controller instrument package and an arbor supported by bearings. The arbor forms an interior cylinder and is encircled by a stationary slip ring though which are ported hydraulic passageways into the interior cylinder of the arbor such that a piston housed therein may be moved axially. Coupled to the piston is a pin tool which is treaded on its lower end and which is moveably seated in, and extending through, a shoulder housing having concave lower face. When welding, the rotating treaded end of the pin enters and stirs the workpieces while the lower face of the shoulder housing compacts the workpieces. As the welding head traverses the shoulder housing the controller senses any rising pressure on the lower face of the shoulder housing and withdraws the arbor to keep the pressure constant. At the same time, the piston moves towards the workpieces thus extending the pin further from the shoulder. This keeps the pin at a proper depth in the workpieces regardless of their thicknesses. As the weld terminates this same operation can be used to incrementally withdraw the pin during the final part of the traverse, thus eliminating any keyhole or crater that would otherwise be created.

  9. Characterization of Multilayered Multipass Friction Stir Weld on ASTM A572 G50 Steel

    SciTech Connect

    Lim, Yong Chae; Sanderson, Samuel; Mahoney, Murray; Yu, Xinghua; Qiao, Dongxiao; Wang, Yanli; Zhang, Wei; Feng, Zhili

    2014-01-01

    A multilayered multipass friction stir weld (MM-FSW) on ASTM A572 Grade 50 steel was characterized to understand its potential application for thick-section structures. The 15-mm-thick section was fabricated by stacking up three steel plates and then friction stir welding the plates together in a total of 5 passes. The unique butt/lap joint configuration encountered in the multilayer weld was examined to understand the effect of tool rotation direction on the joint quality especially the formation of hooking defect. Charpy V-notch impact toughness tests showed generally higher impact toughness energy for the stir zone than the base metal with a ductile fracture mode. The microhardness value was measured from 195 to 220 HV in the stir zone, while the base metal showed an average value of 170 HV. The microstructure in the stir zone and the adjacent heat affected zone was quantified using Optical and Scanning Electron Microscopy (SEM) including Electron Backscatter Diffraction (EBSD). The increased toughness and hardness were correlated with the refined microstructure in stir zone, resulting from severe plastic deformation and subsequent dynamic recrystallization during friction stir welding.

  10. Characterization of Multilayered Multipass Friction Stir Weld on ASTM A572 G50 Steel

    DOE PAGES

    Lim, Yong Chae; Sanderson, Samuel; Mahoney, Murray; ...

    2014-01-01

    A multilayered multipass friction stir weld (MM-FSW) on ASTM A572 Grade 50 steel was characterized to understand its potential application for thick-section structures. The 15-mm-thick section was fabricated by stacking up three steel plates and then friction stir welding the plates together in a total of 5 passes. The unique butt/lap joint configuration encountered in the multilayer weld was examined to understand the effect of tool rotation direction on the joint quality especially the formation of hooking defect. Charpy V-notch impact toughness tests showed generally higher impact toughness energy for the stir zone than the base metal with a ductilemore » fracture mode. The microhardness value was measured from 195 to 220 HV in the stir zone, while the base metal showed an average value of 170 HV. The microstructure in the stir zone and the adjacent heat affected zone was quantified using Optical and Scanning Electron Microscopy (SEM) including Electron Backscatter Diffraction (EBSD). The increased toughness and hardness were correlated with the refined microstructure in stir zone, resulting from severe plastic deformation and subsequent dynamic recrystallization during friction stir welding.« less

  11. Design and evaluation of improved magnetic stir bars for single-mode microwave reactors.

    PubMed

    Obermayer, David; Damm, Markus; Kappe, C Oliver

    2013-08-14

    Magnetic stirring in sealed cylindrical vessels designed for use in single-mode microwave instruments is typically less than optimal, and is not comparable to the efficient agitation that can be generally obtained in a round-bottomed flask fitted with a suitable magnetic stir bar or using overhead mechanical stirring systems. A new "vertical blade" stir bar design that improves the stirring performance in the very narrow, flow-constricting microwave vessels has been developed and evaluated for several different transformations where stirring and efficient agitation are known to be of importance. The better performance of these novel stirrers compared to the traditional cylindrical stir bar design is not only due to the geometry of the stirrer but also to the utilization of a magnetic material with a stronger magnetic transmission force (Sm2Co17) compared to standard ferrite or AlNiCo alloys. For all three tested cases involving solid/liquid, liquid/liquid and highly viscous reaction systems, the new vertical blade stirrers showed a distinctively improved performance resulting in higher conversions and/or product yields.

  12. Inverse magnetorheological fluids.

    PubMed

    Rodríguez-Arco, L; López-López, M T; Zubarev, A Y; Gdula, K; Durán, J D G

    2014-09-07

    We report a new kind of field-responsive fluid consisting of suspensions of diamagnetic (DM) and ferromagnetic (FM) microparticles in ferrofluids. We designate them as inverse magnetorheological (IMR) fluids for analogy with inverse ferrofluids (IFFs). Observations on the particle self-assembly in IMR fluids upon magnetic field application showed that DM and FM microparticles were assembled into alternating chains oriented along the field direction. We explain such assembly on the basis of the dipolar interaction energy between particles. We also present results on the rheological properties of IMR fluids and, for comparison, those of IFFs and bidispersed magnetorheological (MR) fluids. Interestingly, we found that upon magnetic field application, the rheological properties of IMR fluids were enhanced with respect to bidispersed MR fluids with the same FM particle concentration, by an amount greater than the sum of the isolated contribution of DM particles. Furthermore, the field-induced yield stress was moderately increased when up to 30% of the total FM particle content was replaced with DM particles. Beyond this point, the dependence of the yield stress on the DM content was non-monotonic, as expected for FM concentrations decreasing to zero. We explain these synergistic results by two separate phenomena: the formation of exclusion areas for FM particles due to the perturbation of the magnetic field by DM particles and the dipole-dipole interaction between DM and FM particles, which enhances the field-induced structures. Based on the second phenomenon, we present a theoretical model for the yield stress that semi-quantitatively predicts the experimental results.

  13. The effect of feed rate and recycle rate variable on leaching process of Na2Zro3 with HCl in continuous stirred tank reactor (CSTR) series

    NASA Astrophysics Data System (ADS)

    Palupi, Bekti; Supranto, Sediawan, Wahyudi Budi; Setyadji, Moch.

    2017-05-01

    This time, the natural resources of zircon sand is processed into several zirconium products which is utilized for various industries, such as ceramics, glass industry, metal industry and nuclear industry. The process of zircon sand into zirconium products through several stages, one of them is leaching process of Na2ZrO3 with HCl. In this research, several variations of recycle-rate/feed-rate had been done to determine the effect on leaching process. The leaching was processed at temperature of 90°C, ratio of Na2ZrO3:HCl = 1g:30mL, and 142 rotary per minute of stirring speed for 30 minutes with variation of recycle-rate/feed-rate such as 0.478, 0.299, 0.218, 0.171 and 0.141. The diameter size of Na2ZrO3 powder that used are 0.088 to 0.149 mm. This process was carried out in Continuous Stirred Tank Reactor (CSTR) series with recycle. Based on this research, the greater of the recycle-rate/feed-rate variable, the obtained Zr recovery decreased. The correlation between recycle-rate/feed-rate and Zr recovery is shown by the equation y = -146.91x + 103.51, where y is the Zr recovery and x is the recycle-rate/feed-rate. The highest Zr recovery was 90.52% obtained at recycle-rate/feed-rate 0.141. The mathematical modeling involving the probability model P(r) = 2β2r2 exp(-βr2) can be applied to this leaching process with Sum of Squared Errors (SSE) values in the range of 6×10-7 - 7×10-6.

  14. Wavelet Sparse Approximate Inverse Preconditioners

    NASA Technical Reports Server (NTRS)

    Chan, Tony F.; Tang, W.-P.; Wan, W. L.

    1996-01-01

    There is an increasing interest in using sparse approximate inverses as preconditioners for Krylov subspace iterative methods. Recent studies of Grote and Huckle and Chow and Saad also show that sparse approximate inverse preconditioner can be effective for a variety of matrices, e.g. Harwell-Boeing collections. Nonetheless a drawback is that it requires rapid decay of the inverse entries so that sparse approximate inverse is possible. However, for the class of matrices that, come from elliptic PDE problems, this assumption may not necessarily hold. Our main idea is to look for a basis, other than the standard one, such that a sparse representation of the inverse is feasible. A crucial observation is that the kind of matrices we are interested in typically have a piecewise smooth inverse. We exploit this fact, by applying wavelet techniques to construct a better sparse approximate inverse in the wavelet basis. We shall justify theoretically and numerically that our approach is effective for matrices with smooth inverse. We emphasize that in this paper we have only presented the idea of wavelet approximate inverses and demonstrated its potential but have not yet developed a highly refined and efficient algorithm.

  15. Disaster Debris Recovery Database - Recovery

    EPA Pesticide Factsheets

    The US EPA Region 5 Disaster Debris Recovery Database includes public datasets of over 6,000 composting facilities, demolition contractors, transfer stations, landfills and recycling facilities for construction and demolition materials, electronics, household hazardous waste, metals, tires, and vehicles in the states of Illinois, Indiana, Iowa, Kentucky, Michigan, Minnesota, Missouri, North Dakota, Ohio, Pennsylvania, South Dakota, West Virginia and Wisconsin.In this update, facilities in the 7 states that border the EPA Region 5 states were added to assist interstate disaster debris management. Also, the datasets for composters, construction and demolition recyclers, demolition contractors, and metals recyclers were verified and source information added for each record using these sources: AGC, Biocycle, BMRA, CDRA, ISRI, NDA, USCC, FEMA Debris Removal Contractor Registry, EPA Facility Registry System, and State and local listings.

  16. Ultrasonic-assisted friction stir welding on V95AT1 (7075) aluminum alloy

    NASA Astrophysics Data System (ADS)

    Tarasov, S. Yu.; Rubtsov, V. Ye.; Kolubaev, E. A.; Ivanov, A. N.; Fortuna, S. V.; Eliseev, A. A.

    2015-10-01

    Ultrasonic-assisted friction stir butt welding on aluminum alloy V95AT1 (7075) has been carried out. Samples have been characterized using metallography, microhardness and XRD. As shown, ultrasonic treatment during welding provides extra plasticizing of metal and better stirring efficiency. The latter serves for elimination of defects, such as root flaw and grain refining in the stir zone. The stress state in the welded joint is characterized by tensile stress in the direction of the weld seam centerline and compression in the transversal direction. The ultrasonic treatment was shown to increase the compression stress and relieve the tensile one.

  17. Stability of Y–Ti–O precipitates in friction stir welded nanostructured ferritic alloys

    DOE PAGES

    Yu, Xinghua; Mazumder, B.; Miller, M. K.; ...

    2015-01-19

    Nanostructured ferritic alloys, which have complex microstructures which consist of ultrafine ferritic grains with a dispersion of stable oxide particles and nanoclusters, are promising materials for fuel cladding and structural applications in the next generation nuclear reactor. This paper evaluates microstructure of friction stir welded nanostructured ferritic alloys using electron microscopy and atom probe tomography techniques. Atom probe tomography results revealed that nanoclusters are coarsened and inhomogeneously distributed in the stir zone and thermomechanically affected zone. Three hypotheses on coarsening of nanoclusters are presented. Finally, the hardness difference in different regions of friction stir weld has been explained.

  18. Effects of Fusion Tack Welds on Self-Reacting Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Pendleton, M. L.; Brooke, S. A.; Russell, C. K.

    2012-01-01

    In order to know whether fusion tack welds would affect the strength of self-reacting friction stir seam welds in 2195-T87 aluminum alloy, the fracture stresses of 144 tensile test coupons cut from 24 welded panels containing segments of friction stir welds were measured. Each of the panels was welded under unique processing conditions. A measure of the effect of the tack welds for each panel was devised. An analysis of the measures of the tack weld effect supported the hypothesis that fusion tack welds do not affect the strength of self-reacting friction stir welds to a 5% level of confidence.

  19. Tensile strength on friction stir processed AMg5 (5083) aluminum alloy

    NASA Astrophysics Data System (ADS)

    Chumaevsky, A. V.; Eliseev, A. A.; Filippov, A. V.; Rubtsov, V. E.; Tarasov, S. Yu.

    2016-11-01

    The results of the tensile tests carried out both on AMg5 (5083) aluminum alloy samples base and those obtained using friction stir processing technique are reported. The tensile test samples have been prepared from the friction stir processed plates so that their tensile axis was parallel to the processing direction. The maximum tensile strength of the processed samples was 9% higher than of the base metal. The fractographic examination shows the presence of flat areas inherent of the brittle fracture in all three friction processed samples. The load-extension curves show that friction stir processing may suppress the serrated yielding.

  20. Effect of cooling rate on microstructure of friction-stir welded AA1100 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Yi, D.; Mironov, S.; Sato, Y. S.; Kokawa, H.

    2016-06-01

    In this work, the microstructural changes occurring during cooling of friction-stir welded aluminum alloy AA1100 were evaluated. To this end, friction-stir welding (FSW) was performed in a wide range of cooling rates of 20-62 K/s and the evolved microstructures were studied by using electron backscatter diffraction. Below 0.6 Tm (Tm being the melting point), the stir zone material was found to experience no significant changes during cooling. At higher FSW temperatures, however, notable changes occurred in the welded material, including grain growth, sharpening of texture, reduction of the fraction of high-angle boundaries and material softening.