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  • 1
    Electronic Resource
    Electronic Resource
    Comparative study of rest technetium-99m sestamibi SPET and low-dose dobutamine stress echocardiography for the early assessment of myocardial viability after acute myocardial infarction: importance of the severity of the infarct-related stenosis (1996)
    Springer
    European journal of nuclear medicine 23 (1996), S. 748-755 
    Details
    ISSN: 1619-7089
    Keywords: Myocardial infarction ; Technetium-99m sestamibi ; Dobutamine stress echocardiography ; Coronary anatomy ; Viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rest technetium-99m sestamibi single-photon emission tomography (SPET) has been shown to under-estimate viability in some patients with chronic ischaemic myocardial dysfunction. The present study was designed to appraise the value of99mTc-sestamibi as a viability tracer in patients with a recent myocardial infarction and to determine factors that might influence its accuracy in assessing infarct size. Therefore, rest99mTc-sestamibi SPET, low-dose dobutamines stress echocardiography and quantitative coronary angiography were performed in 51 patients with a recent myocardial infarction. Perfusion activity and regional wall motion were scored semi-quantitatively using the same segmental division of the left ventricle. Assessment of99mTc-sestamibi uptake as a marker of viability was performed by comparing a binary uptake score (viable=〉50% vs necrotic =≤50% of the maximal tracer activity) with a binary wall motion classification during low-dose dobutamine infusion (viable=normal/hypokinetic vs necrotic=akinetic/dyskinetic). Infarct size, expressed as the number of segments with evidence of necrotic tissue, was significantly greater in the scintigraphic study than in the echocardiographic study (2.8±1.5 vs 2.2±1.3,P=0.006). This overestimation of infarct size by99mTc-sestamibi was present only in patients with a severe infarct-related stenosis (% diameter stenosis ≽65%–100%) and particularly those with “late” reperfusion therapy (time delay ≽180 min). In patients without a severe infarct-related stenosis,99mTc-sestamibi was able to accurately distinguish viable from necrotic segments. Thus, rest99mTc-sestamibi scintigraphy early after acute myocardial infarction may underestimate residual viability within the infarct region, particularly in patients with low flow state coronary anatomy, as a result of a severe infarct-related stenosis and/or late reperfusion therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00843702
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  • 2
    Electronic Resource
    Electronic Resource
    Adenosine technetium-99m sestamibi single-photon emission tomography for the assessment of jeopardized myocardium early after acute myocardial infarction (1997)
    Springer
    European journal of nuclear medicine 24 (1997), S. 1121-1127 
    Details
    ISSN: 1619-7089
    Keywords: Jeopardized myocardium ; Adenosine ; Technetium-99m sestamibi ; Stenosis severity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigated the value of technetium-99m sestarnibi scintigraphy in identifying patients at risk for post-infarct ischaemia (=jeopardized myocardium), especially within the reperfused infarct region. In 51 patients with a recent (〈I month) myocardial infarction, adenosine99mTc-sestamibi single-photon emission tomography (SPET) and dobutamine stress echocardiography (DSE) were performed and correlated with the presence of significant coronary artery stenosis [% diameter stenosis (DS) 〉50%] on quantitative coronary angiography. Regional perfusion activity was analysed semiquantitatively (score 0–4) on a 13-segment left ventricular model. DSE was used for the estimation of the infarct size (low-dose DSE) and for concomitant evaluation of ischaemia (high-dose DSE). A reversible perfusion defect within the infarct region was observed in 20 of the 37 patients with a significant infarct-related lesion (sensitivity of 54%) and only in one patient without a significant infarct-related lesion (specificity of 93%). Further analysis revealed that the scintigraphic assessment of jeopardized myocardium was fairly good in patients with a moderate (DS 51%–64%) infarct-related stenosis but was inadequate in patients with a severe (DS≥65%) infarct-related stenosis (sensitivity of 80% vs 36%,P〈0.01), while the echocardiographic detection of ischaemia was not influenced by stenosis severity (sensitivity of 73% in both subgroups). This scintigraphic under-estimation of jeopardized myocardium was mainly related to a severely impaired myocardial perfusion under baseline conditions, as was evidenced by a significantly more severe rest perfusion score in the infarct region in patients with a severe stenosis as compared to those with a moderate stenosis (average score: 1.5±0.7 vs 2.1±0.6,P〈0.01), while infarct size on echocardiography was similar for both subgroups. It may be concluded that early after an acute myocardial infarction, adenosine99mTc-sestamibi SPET may underestimate reperfused but still jeopardized myocardium, particularly in patients with a severe infarct-related stenosis. In these patients the evaluation of the ischaemic burden on rest-stress scintigraphy is hampered by the presence of a severely impaired myocardial perfusion in resting conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01254243
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  • 3
    Electronic Resource
    Electronic Resource
    Adenosine technetium-99m sestamibi single-photon emission tomography for the assessment of jeopardized myocardium early after acute myocardial infarction (1997)
    Springer
    European journal of nuclear medicine 24 (1997), S. 1121-1127 
    Details
    ISSN: 1619-7089
    Keywords: Key words: Jeopardized myocardium ; Adenosine ; Technetium-99m sestamibi ; Stenosis severity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. This study investigated the value of technetium-99m sestamibi scintigraphy in identifying patients at risk for post-infarct ischaemia (=jeopardized myocardium), especially within the reperfused infarct region. In 51 patients with a recent (〈1 month) myocardial infarction, adenosine 99mTc-sestamibi single-photon emission tomography (SPET) and dobutamine stress echocardiography (DSE) were performed and correlated with the presence of significant coronary artery stenosis [% diameter stenosis (DS) 〉50%] on quantitative coronary angiography. Regional perfusion activity was analysed semi-quantitatively (score 0–4) on a 13-segment left ventricular model. DSE was used for the estimation of the infarct size (low-dose DSE) and for concomitant evaluation of ischaemia (high-dose DSE). A reversible perfusion defect within the infarct region was observed in 20 of the 37 patients with a significant infarct-related lesion (sensitivity of 54%) and only in one patient without a significant infarct-related lesion (specificity of 93%). Further analysis revealed that the scintigraphic assessment of jeopardized myocardium was fairly good in patients with a moderate (DS 51%–64%) infarct-related stenosis but was inadequate in patients with a severe (DS≥65%) infarct-related stenosis (sensitivity of 80% vs 36%, P〈0.01), while the echocardiographic detection of ischaemia was not influenced by stenosis severity (sensitivity of 73% in both subgroups). This scintigraphic underestimation of jeopardized myocardium was mainly related to a severely impaired myocardial perfusion under baseline conditions, as was evidenced by a significantly more severe rest perfusion score in the infarct region in patients with a severe stenosis as compared to those with a moderate stenosis (average score: 1.5±0.7 vs 2.1±0.6, P〈0.01), while infarct size on echocardiography was similar for both subgroups. It may be concluded that early after an acute myocardial infarction, adenosine 99mTc-sestamibi SPET may underestimate reperfused but still jeopardized myocardium, particularly in patients with a severe infarct-related stenosis. In these patients the evaluation of the ischaemic burden on rest-stress scintigraphy is hampered by the presence of a severely impaired myocardial perfusion in resting conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01254243
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  • 4
    Electronic Resource
    Electronic Resource
    AC and DC dielectric properties of some polypropylene/calcium carbonate composites (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 374-383 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: AC dielectric properties and thermally stimulated polarization (TSP) and depolarization (TSD) currents were studied in a series of CaCO3-filled polypropylene composites. The filler content (0 to 50 weight percent) and the average particle size (3.0 to 16.1 μm) at constant filler content (30 weight percent) were varied in separate groups of samples. In a third group of samples the filler (20 to 40 weight percent) was surface treated with stearates. The AC dielectric behavior of composites containing untreated fillers is largely determined by a small amount of adsorbed water. Upon heating, the dielectric properties show maxima (increasing with decreasing frequency) which disappear on cooling. In the case of stearate-treated fillers the dielectric loss level is higher, the dispersion and loss curves on heating reflect a combination of dipolar and protonic processes with water desorption. In the dry state the onset of an audio frequency relaxation process is observed in the pre-melting zone. The thermally stimulated currents of the composites containing treated and untreated fillers are also different. In the case of the untreated fillers the TSP curves show maxima indicating water desorption which are increasingly intense and roughly exponential with filler content. The high temperature conductivity and the intensity of the pre-melting depolarization peak pass through a minimum as a function of filler content. Above 20 weight percent filler content the activation energy of high temperature conductivity decreases. In the case of the surface treated samples, the thermally stimulated response is different for “wet” and dried samples. The dry samples exhibit a relaxation between the amorphous and crystalline transitions of the matrix polymer which is probably due to interfacial relaxation caused by the enhanced surface conductivity of the stearate-treated fillers.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300609
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature profiles for polymer melts in tube flow (1970)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 16 (1970), S. 339-344 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The present state of the theory of nonisothermal tube flow is inadequate to predict the behavior of polymer melts. In addition, relatively few experimental measurements on radial temperature profiles of polymer melts in the tube flow have been reported. For non-Newtonian systems, the separation of viscous losses due to frictional heat generation and those due to the effect of shear rate is a formidable problem which has hampered progress. This paper will describe a method of measuring shear induced heating and present experimental data on radial temperature profiles in tube flow. A novel method of estimating the velocity profile is also described.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690160305
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  • 6
    Electronic Resource
    Electronic Resource
    Compatible glassy polyblends based upon poly(2,6-dimethyl-1,4-phenylene oxide): Tensile modulus studies (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 519-524 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical behavior of compatible glassy polyblends based upon poly(2.6-dimethyl- 1,4-phe nylene oxide) (PPO) was investigated. In particular, the influence of composition, molecular weight, and molecular weight distribution upon the tensile modulus of the blend was assessed. Various possible correlations between the experimentally determined moduli and theory are considered. Included are correlations with density, packing density, composite theory, and lattice fluid theory. The modeling of the properties of mixtures via Simplex lattice design is also presented. Finally, attention is given to the development of compatibility criteria based upon tensile modulus and density measurements.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190710
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of phase separation on the mechanical properties of polystyrene/poly(vinyl methyl ether) blends (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 981-987 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effects of phase separation temperature and time on the tensile, dynamic mechanical, and tear properties of blends of polystyrene and poly(vinyl methyl ether) were investigated after phase separation above their respective cloud points with specified temperature-annealing time protocols. The results are analyzed in terms of the phase connectivity, interfacial adhesion, and changes in the glass transition temperature.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311308
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  • 8
    Electronic Resource
    Electronic Resource
    Curing and heat transfer in polyurethane reaction moldingPresented in part at the AiChE Annual Meeting, Chicago, 1976. (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 382-387 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Temperature measurements were made on the adiabatic polymerization of three urethane systems; two casting formulations, one thermoplastic and the other thermosetting, and a commercial reaction injection molding (RIM) formulation with a 10 second gel time. The data were found to fit a simple nth order overall kinetic expression. These kinetic and heat of reaction results were used to model heat transfer in a 3.8 cm diameter cylinder with an isothermal wall. Experimental temperature profiles for the two casting urethanes were in good agreement with predictions. The kinetic data on the RIM material was used to model temperature profiles1 in 3 and 6 mm thick plaque molds. Experimental measurements of temperature near the mold center agreed with the model. Temperatures measured near the wall were higher due to failure of the isothermal wall assumption.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760180509
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal and electrical properties of some epoxy based composites (1990)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 11 (1990), S. 133-143 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Thermally stimulated creep compliance, differential scanning calorimetric behavior, thermal degradation, AC dielectric permittivity and loss (between 120 Hz and 100 kHz) and thermally stimulated polarization and aepolarization currents were studied in a cycloaliphatic epoxy resin (B), in a conventional bisphenol-A-diglycidyl ester type epoxy resin (C) and in composites consisting of: resin B/wollastonite (B/W), resin B/quartz (B/Q) and resin C/wollastonite (C/W). The filler content was 60 wt%. Resin B exhibited higher Tg and lower rubbery deformability than resin C due to its more compact structure. Fillers reduced the rubbery deformation and thermal expansion and shifted the transition temperatures by a few degrees. The shift depended on the method used. Composites B/W and C/W exhibited higher thermal stability than the corresponding pure resins, while sample B/Q was less stable than resin B. Resins B and C exhibited a low temperature β transition (in the case of resin B a doublet) and a high temperature α or glass transition. AC dielectric losses were fairly similar in samples B and B/W, while the high temperature loss of sample B/Q was determined by a space charge process probably due to the matrix/filler interface. In samples C and C/W the α transition is visible but it is superposed on a strong space charge process due to the resin/electrode interface. Thermally stimulated currents show a behavior qualitatively in agreement with the AC results but the very low effective frequency and the nonlinear field strength dependence of the space charge processes cause some minor differences.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750110302
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