bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress corrosion cracking behaviour of Al‐Li alloy 8090‐T8171 plate exposed to various synthetic environments
Authors: Braun R. 
Published: March 2004

AbstractThe stress corrosion cracking (SCC) behaviour of 8090‐T8171 plate material was investigated in short transverse direction performing constant load tests and constant extension rate tests under permanent immersion conditions. At an applied stress of 100 MPa, smooth round tensile specimens were exposed to synthetic environments containing chlorides and various nonhalide anions. Environment‐induced cracking was not observed in aqueous solutions of 0.6 M NaCl, LiCl, NH4Cl, or MgCl2. In 0.6 M NaCl solutions containing 0.06 M Na2SO4 or Na3PO4, the SCC behaviour of 8090‐T8171 plate was similar to that observed in pure 0.6 M NaCl solution. Sodium chloride solutions with additions of nitrate, hydrogen carbonate, or carbonate promoted stress corrosion cracking. Threshold stresses below 100 MPa were obtained from constant load tests using the latter environments. When sodium sulfite or sodium hydrogen phosphate was added, values being 100 MPa or slightly higher were determined. Lithium and ammonium present as cations in mixed salt electrolytes accelerated SCC failure. Lithium chloride solutions containing nitrate, hydrogen carbonate, carbonate, or sulfite were highly conducive to stress corrosion cracking. Very low SCC resistance was found for alloy 8090‐T8171 exposed to synthetic environments with additions of ammonium salts. Constant extension rate tests were carried out using notched tensile specimens. Displacement rates were in the range 2 × 10−6 − 2 × 10−5 mms−1. Aqueous 0.6 M NaCl solutions with additions of 0.06 M NH4HCO3, (NH4)2SO4, or Li2CO3 promoted environment‐induced cracking with 8090‐T8171 plate, as indicated by severe degradation of notch strength. The constant extension rate testing technique did not indicate SCC susceptibility using sodium chloride solutions containing sodium sulfate or lithium sulfate. For specimens exposed to substitute ocean water a slight degradation of notch strength was found at the lowest displacement rate applied.
Effect of Co and W on the corrosion behaviour of 1% Cr steel in flowing synthetic seawater
Authors: Choi Yoon‐Seak , Shim Jae‐Joo , Kim Jung‐Gu 
Published: March 2004

AbstractThe aqueous corrosion characteristics of 1% Cr‐steel alloyed with small amounts of Co and W in synthetic seawater was studied by using immersion weight‐loss tests, electrochemical corrosion tests (potentiodynamic tests and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. 1% Cr steels containing Co or W from 0.2 to 0.4 wt.% showed higher corrosion resistance than the 1% Cr steel in the immersion and potentiodynamic tests. EIS measurements showed that the Nyquist plot presented one time constant. Furthermore, the Co‐ and W‐bearing steels present higher Rp values than the 1% Cr steel through all the test period. The better corrosion resistance of the Co‐and W‐bearing steels is attributed to the protectiveness of the surface layer. The corrosion products were examined using electron probe microanalysis (EPMA) and X‐ray photoelectron spectroscopy (XPS). The results of EPMA indicated that Cr was concentrated in the inner region of the rust layer, while Co and W were distributed all over the rust layer. XPS results showed that Co existed as a trivalent oxide in the rust layer and W in the rust appeared in the form of a WO4 compound. These compounds act as a factor for corrosion resistance in aqueous solutions.
Hochfeste Stangen aus NiCr23Mo16Al – Einfluss der Kaltverfestigung auf die mechanischen Eigenschaften und das Korrosionsverhalten
Authors: Brill U. 
Published: March 2004

AbstractBei hohen Anforderungen an die mechanischen Eigenschaften in Kombination mit besonders korrosiven Umgebungsbedingungen werden häufig kaltverfestigte NiCrMo‐Legierungen eingesetzt.In dieser Arbeit wurde der Einfluss einer durch Ziehen eingebrachten Kaltverformung bis zu 42% auf die mechanischen Eigenschaften und das Korrosionsverhalten der Legierung NiCr23Mo16Al untersucht.Bei den bei 20°C, 204°C und 371°C durchgeführten Zugversuchen wies die 0,2%‐Streckgrenze bis zur maximalen Kaltverformung von 42% eine lineare Steigerung auf. Bei allen Kaltverfestigungsgraden und allen Prüftemperaturen wurden im Zugversuch mindestens 16% Bruchdehnung erreicht. Auch die Kerbschlagarbeit lag selbst bei Prüftemperaturen bis zu − 40°C bei ca. 200 J.Die nach ASTM G 28 A/B und G 48 C/D durchgeführten Korrosionsuntersuchungen weisen bei 42% Kaltverformung keine Verschlechterung des Korrosionsverhaltens gegenüber dem lösungsgeglühten Ausgangszustand auf. Lediglich zwischen ca. 15–30% Kaltverformung deutet sich ein geringfügig ungünstigeres Verhalten an, dass durch eine starke Gefügeinhomogenität und als Folge davon als Lokalelementbildung zwischen stark verformtem Rand und unverformter Mitte erklärt wird.Bei den in 1 M NaCl aufgenommenen Stromdichte‐Potential‐Kurven nach ASTM G 61/98 konnte kein Einfluss der Kaltverformung auf das elektrochemische Verhalten nachgewiesen werden.
On Ethylene Polymerisation with Aluminium and Scandium Complexes: DFT and Post‐HF Calculations
Authors: Meier Robert J. , Koglin Eckhard 
Published: March 2004

AbstractSummary: The performance of Density Functional Theory (DFT) methods in predicting ethylene polymerisation and/or oligomerisation activity in selected aluminium and scandium based complexes was studied using both DFT and post‐Hartree‐Fock CCSD(T) calculations. Whereas previous reports have drawn attention to the underestimation of the barrier for the β‐hydrogen termination process for a few aluminium based species, we found that the same holds for the corresponding scandium complexes. New, however, is the observation that apart from underestimating the energy barrier connected to β‐hydrogen termination, the insertion of ethylene is also severely underestimated by the DFT methods applied compared to post‐Hartree‐Fock calculations up to the CCSD(T) level.Structure of the diketiminate complex referred to in the text.imageStructure of the diketiminate complex referred to in the text.
Chromosome 17p13.2 transfer reverts transformation phenotypes and fas‐mediated apoptosis in breast epithelial cells
Authors: Lareef Mohamed H. , Tahin Quivo , Song Joon , Russo Irma H. , Mihaila Dana , Slater Carolyn M. , Balsara Binaifer , Testa Joseph R. , Broccoli Dominique , Grobelny Jennifer V. , Mor Gil , Cuthbert Andrew , Russo Jose 
Published: March 2004

AbstractTransformation of the human breast epithelial cells (HBEC) MCF‐10F with the carcinogen benz(a)pyrene (BP) into BP1‐E cells resulted in the loss of the chromosome 17 p13.2 locus (D17S796 marker) and formation of colonies in agar‐methocel (colony efficiency (CE)), loss of ductulogenic capacity in collagen matrix, and resistance to anti‐Fas monoclonal antibody (Mab)‐induced apoptosis. For testing the role of that specific region of chromosome 17 in the expression of transformation phenotypes, we transferred chromosome 17 from mouse fibroblast donors to BP1‐E cells. Chromosome 11 was used as negative control. After G418 selection, nine clones each were randomly selected from BP1‐E‐11neo and BP1‐E‐17neo hybrids, respectively, and tested for the presence of the donor chromosomes by fluorescent in situ hybridization and polymerase chain reaction‐based restriction fragment length polymorphism (PCR‐RFLP) analyses. Sensitivity to Fas Mab–induced apoptosis and evaluation of transformation phenotype expression were tested in MCF‐10F, BP1‐E, and nine BP1‐E‐11neo and BP1‐E‐17neo clones each. Six BP1‐E‐17neo clones exhibited a reversion of transformation phenotypes and a dose dependent sensitivity to Fas Mab‐induced apoptosis, behaving similarly to MCF‐10F cells. All BP1‐E‐11neo, and three BP1‐E‐17neo cell clones, like BP1‐E cells, retained a high CE, loss of ductulogenic capacity, and were resistant to all Fas Mab doses tested. Genomic analysis revealed that those six BP1‐E‐17neo clones that were Fas‐sensitive and reverted their transformed phenotypes had retained the 17p13.2 (D17S796 marker) region, whereas it was absent in all resistant clones, indicating that the expression of transformation phenotypes and the sensitivity of the cells to Fas‐mediated apoptosis were under the control of genes located in this region. © 2004 Wiley‐Liss, Inc.
Measurement of aroma compound self‐diffusion in food models by DOSY
Authors: Gostan Thierry , Moreau Céline , Juteau Alexandre , Guichard Elisabeth , Delsuc Marc‐André 
Published: March 2004

AbstractSelf‐diffusion measurement of solutes in polymer gels has been investigated using pulsed gradient spin echo NMR spectroscopy. However, few data are available on the self‐diffusion of small solutes in natural polysaccharide polymers used as thickeners in the food industry. Since aroma diffusion in food matrices could have an impact on flavor release, this is an interesting and economic challenge. Diffusion ordered spectroscopy (DOSY) resolves diffusion data for each component in complex mixtures. We used DOSY with the inverse Laplace transform approach with the maximum entropy algorithm to investigate diffusion of two aroma compounds, ethyl butanoate and linalool, in an ι‐carrageenan matrix as the food model. We showed that the self‐diffusion coefficient values of small molecules in a polysaccharide matrix could be easily extracted using this method. We then investigated the impact of the gelling state of ι‐carrageenan matrices on the self‐diffusion of ethyl butanoate. Copyright © 2004 John Wiley & Sons, Ltd.
Exploring lung function with hyperpolarized 129Xe nuclear magnetic resonance
Authors: Ruppert Kai , Mata Jaime F. , Brookeman James R. , Hagspiel Klaus D. , Mugler John P. 
Published: March 2004

AbstractWith the use of polarization‐transfer pulse sequences and hyperpolarized 129Xe NMR, gas exchange in the lung can be measured quantitatively. However, harnessing the inherently high sensitivity of this technique as a tool for exploring lung function requires a fundamental understanding of the xenon gas‐exchange and diffusion processes in the lung, and how these may differ between healthy and pathological conditions. Toward this goal, we employed NMR spectroscopy and imaging techniques in animal models to investigate the dependence of the relative xenon gas exchange rate on the inflation level of the lung and the tissue density. The spectroscopic results indicate that gas exchange occurs on a time scale of milliseconds, with an average effective diffusion constant of about 3.3 × 10−6cm2/s in the lung parenchyma. Polarization‐transfer imaging pulse sequences, which were optimized based on the spectroscopic results, detected regionally increased gas‐exchange rates in the lung, indicative of increased tissue density secondary to gravitational compression. By exploiting the gas‐exchange process in the lung to encode physiologic parameters, these methods may be extended to noninvasive regional assessments of lung‐tissue density and the alveolar surface‐to‐volume ratio, and allow lung pathology to be detected at an earlier stage than is currently possible. Magn Reson Med 51:676–687, 2004. © 2004 Wiley‐Liss, Inc.
EPR oximetry in the beating heart: Myocardial oxygen consumption rate as an index of postischemic recovery
Authors: Ilangovan Govindasamy , Liebgott Thibaut , Kutala Vijay Kumar , Petryakov Sergey , Zweier Jay L. , Kuppusamy Periannan 
Published: March 2004

AbstractOxygen plays a critical role in the pathophysiology of myocardial injury during both ischemia and subsequent reperfusion (I/R). Thus, oxygen concentration is an important variable to measure during I/R. In the present work, electron paramagnetic resonance (EPR)‐based oximetry was used to measure the oxygen concentration during a series of I/R episodes and oxygenation levels were correlated with the contractile and hemodynamic functions of the heart. A custom‐developed electronically tunable surface coil resonator working at 1.1 GHz was used to determine tissue pO2 in the beating heart. Microcrystalline particulate of lithium phthalocyanine was used as an EPR oximetry probe. Isolated and perfused rat hearts were subjected to 1 or 3 hr durations of preischemic perfusion, followed by 15‐min I/R cycles. In hearts perfused for 3 hr prior to 15‐min I/R cycles, the myocardial pO2 decreased gradually on subsequent reperfusions of three successive I/R cycles. However, in hearts perfused for 1 hr there was almost 100% recovery of myocardial pO2 in all three I/R cycles. The extent of oxygenation recovered in each reperfusion cycle correlated with the recovery of hemodynamic and contractile function. The results also showed that the oxygen consumption rate of the heart at the end of each I/R episode decreased in direct proportion to the functional recovery. In summary, it was observed that the amount of myocardial oxygen consumption during I/R could provide a reliable index of functional impairment in the heart. Magn Reson Med 51:835–842, 2004. © 2004 Wiley‐Liss, Inc.
Novel pH‐sensitive paramagnetic liposomes with improved MR properties
Authors: Løkling Knut‐Egil , Skurtveit Roald , Bjørnerud Atle , Fossheim Sigrid L. 
Published: March 2004

AbstractThe use of paramagnetic pH‐sensitive liposomes was recently suggested as a new approach for monitoring pathologic changes in pH by MRI. Such liposomes must be stable in blood and selectively release the encapsulated paramagnetic agent when exposed to lower pH in the target tissue. In the present study, different liposomal systems were formulated and characterized by relaxometry, cryo‐transmission electron microscopy (cryo‐TEM), and MRI. The pH‐sensitive system dipalmitoylphosphatidylethanolamine/palmitic acid (DPPE/PA) liposomal GdDTPA‐BMA, which was previously shown to be unstable in blood, was modified to improve its stability. The incorporation of cholesterol into the DPPE/PA liposomes significantly increased their stability in blood, but the pH sensitivity was diminished. Polyethylene glycol (PEG)‐modified DPPE/PA liposomes were pH‐insensitive in buffer, and unstable in blood. However, exchanging PA with the double‐chained amphiphile dipalmitoylglycerosuccinate (DPSG) yielded liposomes with improved properties. DPPE/DPSG liposomal GdDTPA‐BMA was stable in blood at physiological pH, and displayed a marked pH sensitivity. The pH sensitivity was not diminished after preincubation in blood, contrary to what has been reported for analogues containing unsaturated lipids. The potential of this system for monitoring pH was demonstrated in an in vitro MRI phantom study. Magn Reson Med 51:688–696, 2004. © 2004 Wiley‐Liss, Inc.
Parallel excitation with an array of transmit coils
Authors: Zhu Yudong 
Published: March 2004

AbstractTheoretical and experimental results are presented that establish the value of parallel excitation with a transmit coil array in accelerating excitation and managing RF power deposition. While a 2D or 3D excitation pulse can be used to induce a multidimensional transverse magnetization pattern for a variety of applications (e.g., a 2D localized pattern for accelerating spatial encoding during signal acquisition), it often involves the use of prolonged RF and gradient pulses. Given a parallel system that is composed of multiple transmit coils with corresponding RF pulse synthesizers and amplifiers, the results suggest that by exploiting the localization characteristics of the coils, an orchestrated play of shorter RF pulses can achieve desired excitation profiles faster without adding strains to gradients. A closed‐form design for accelerated multidimensional excitations is described for the small‐tip‐angle regime, and its suppression of interfering aliasing lobes from coarse excitation k‐space sampling is interpreted based on an analogy to sensitivity encoding (SENSE). With or without acceleration, the results also suggest that by taking advantage of the extra degrees of freedom inherent in a parallel system, parallel excitation provides better management of RF power deposition while facilitating the faithful production of desired excitation profiles. Sample accelerated and specific absorption rate (SAR)‐reduced excitation pulses were designed in this study, and evaluated in experiments. Magn Reson Med 51:775–784, 2004. © 2004 Wiley‐Liss, Inc.
3D DT‐MRI using a reduced‐FOV approach and saturation pulses
Authors: Wang Jiun‐Jie , Deichmann Ralf , Turner Robert , Ordidge Roger 
Published: March 2004

AbstractDiffusion tensor imaging (DTI) can provide vital insights into brain connectivity, and may become an important tool for the diagnosis and treatment of neurological disease. However, DTI's intrinsic low signal‐to‐noise ratio (SNR) and vulnerability to ghosting artifacts can result in poor image quality with low spatial resolution, which limits its clinical applications. In this study, a new double‐shot EPI sequence (half‐FOV EPI) with high spatial resolution was developed. This method enables DT measurements to be obtained with high isotropic spatial resolution and whole‐brain coverage. To avoid ghosting artifacts, the data are combined in image space rather than in k‐space. Magn Reson Med 51:853–857, 2004. © 2004 Wiley‐Liss, Inc.
Correction for partial volume errors in MR heart perfusion imaging
Authors: Köstler Herbert , Ritter Christian , Reiss‐Zimmermann Martin , Beer Meinrad , Hahn Dietbert , Sandstede Jörn 
Published: March 2004

AbstractMyocardial MR first‐pass perfusion time courses are contaminated by signals from the ventricles (spillover) as a consequence of partial volume effects and motion. An early increase in the signal intensity from the myocardium is an indicator of contamination. This contamination leads to under‐ or overestimation of perfusion, depending on the amount of contamination. In this work a simple method for contamination correction is proposed: curves proportional to the signal intensity time courses in the ventricles are subtracted from the signal intensity time courses in the myocardium to minimize the variance of signal before the arrival of the contrast medium in the myocardium. The proposed correction is easy to apply, removes the contamination, and leads to more precise perfusion values. Magn Reson Med 51:848–852, 2004. © 2004 Wiley‐Liss, Inc.
Improved combination of spiral‐in/out images for BOLD fMRI
Authors: Glover Gary H. , Thomason Moriah E. 
Published: March 2004

AbstractAcquisitions with the spiral‐in/out technique result in two separate image timeseries obtained during the spiral‐in and spiral‐out trajectory. In uniform brain regions the two components have comparable signal and BOLD contrast and can be averaged, but in regions compromised by susceptibility effects where both signal and noise can differ in the two images other combination methods may be more effective. Here, several weighting schemes are compared for signal and activation contrast recovery in whole brain and prefrontal cortex using verbal working memory (seven subjects) and breathholding tasks (six subjects) scanned at 3 T. It was found that a statistically weighted combination based on activation maps derived separately from the spiral‐in and spiral‐out images provides activation volumes with increases of 33–59% over second‐choice signal‐weighted combination and 100–200% increases over spiral‐out acquisition alone, and that simple averaging is inferior to signal‐weighted combination. Magn Reson Med 51:863–868, 2004. © 2004 Wiley‐Liss, Inc.
Semiautomatic segmentation and stenosis quantification of 3D contrast‐enhanced MR angiograms of the internal carotid artery
Authors: van Bemmel Cornelis M. , Viergever Max A. , Niessen Wiro J. 
Published: March 2004

AbstractA technique is presented for the segmentation and quantification of stenosed internal carotid arteries (ICAs) in 3D contrast‐enhanced MR angiography (CE‐MRA). Segmentation with sub‐pixel accuracy of the ICA is achieved via level‐set techniques in which the central axis serves as the initialization. The central axis is determined between two user‐defined points, and minimal user interaction is required. For quantification, the cross‐sectional area is measured in the stenosis and at a reference segment in planes perpendicular to the central axis. The technique was applied to 20 ICAs. The variation in measurements obtained by this method in comparison with manual observations was 8.7%, which is smaller than the interobserver variability among three experts (11.0%). Magn Reson Med 51:753–760, 2004. © 2004 Wiley‐Liss, Inc.
Efficient method for calculating kinetic parameters using T1‐weighted dynamic contrast‐enhanced magnetic resonance imaging
Authors: Murase Kenya 
Published: March 2004

AbstractIt has become increasingly important to quantitatively estimate tissue physiological parameters such as perfusion, capillary permeability, and the volume of extravascular‐extracellular space (EES) using T1‐weighted dynamic contrast‐enhanced MRI (DCE‐MRI). A linear equation was derived by integrating the differential equation describing the kinetic behavior of contrast agent (CA) in tissue, from which K1 (rate constant for the transfer of CA from plasma to EES), k2 (rate constant for the transfer from EES to plasma), and Vp (plasma volume) can be easily obtained by the linear least‐squares (LLSQ) method. The usefulness of this method was investigated by means of computer simulations, in comparison with the nonlinear least‐squares (NLSQ) method. The new method calculated the above parameters faster than the NLSQ method by a factor of approximately 6, and estimated them more accurately than the NLSQ method at a signal‐to‐noise ratio (SNR) of < ∼10. This method will be useful for generating functional images of K1, k2, and Vp from DCE‐MRI data. Magn Reson Med 51:858–862, 2004. © 2004 Wiley‐Liss, Inc.
Quantitative assessment of uptake and distribution of iron oxide particles (NC100150) in human melanoma xenografts by contrast‐enhanced MRI
Authors: Graff Bjørn A. , Vangberg Lars , Rofstad Einar K. 
Published: March 2004

AbstractThe intratumor heterogeneity in uptake of iron oxide particles (NC100150) in human melanoma xenografts was studied by MRI and the uptake was related to the blood volume fraction, BV, and the permeability surface area product, PS, in an attempt to identify transport barriers limiting the delivery of large macromolecular therapeutic agents to tumors. Dynamic MRI was performed by using spoiled gradient recalled sequences and the extravascular uptake of NC100150, BV, and PS were calculated for each tumor voxel by using a two‐compartment tissue model. The uptake of NC100150 and BV were low in the tumor center and increased gradually towards the tumor periphery, whereas there was no radial gradient in PS. Significant correlations were found between the voxel values of the parameters. Thus, PS was inversely correlated to BV, and this correlation was stronger in the center than in the periphery of the tumors. The uptake of NC100150 was positively correlated to PS and this correlation was strong in the tumor periphery, where the blood perfusion is high, and weak in the tumor center, where the blood perfusion is low. In contrast, the uptake of NC100150 was not correlated to BV in any tumor region. These observations suggest that the extravascular uptake of NC100150 was limited primarily by the microvascular permeability in the tumor periphery and primarily by the blood perfusion in the tumor center. Magn Reson Med 51:727–735, 2004. © 2004 Wiley‐Liss, Inc.