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  • 2020-2024
  • 1990-1994  (6)
  • 1900-1904
  • Ziegler-Natta catalysts  (4)
  • Metaiodobenzylguanidine  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of polarity of the medium on the stereospecific polymerization of propylene by ansa-zirconocene catalyst (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2049-2056 
    Details
    ISSN: 0887-624X
    Keywords: metallocenes ; olefin polymerizations ; Ziegler-Natta catalysts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Propylene was polymerized with rac-ethylene-bis (1-η5-indenyl)dichlorozirconium/methylaluminoxane in solvents of different polarity. The poly (propylene) formed was separated by solvent extraction; 13C-NMR and DSC measurements were made on the polymer fractions. The poly(propylene) in each solvent fraction has its characteristic molecular weight steric pentad distributions, melting transition temperature, and enthalpy for fusion irrespective of the polymerization medium. The results suggest that the medium dielectric constant does not affect the polymerization rate or the intrinsic stereoselectivity, propagation and chain transfer rates a given catalytic species but can alter the occurrence of steric insertion errors through shifting of distributions of the propagating species producing poly(propylenes) of different stereoregularities. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321106
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  • 2
    Electronic Resource
    Electronic Resource
    Predictors of toxicity in treating patients with neuroblastoma by radiolabeled metaiodobenzylguanidine (1994)
    Springer
    European journal of nuclear medicine 21 (1994), S. 46-52 
    Details
    ISSN: 1619-7089
    Keywords: Metaiodobenzylguanidine ; Therapy ; Toxicity ; Thrombocytopenia ; Dosimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We searched for methods that would enable prescriptions of the maximum tolerable doses of iodine-131 metaiodobenzylguanidine (MIBG) and iodine-125 MIBG in the treatment of patients with neuroblastoma. We correlated doses, defined in different ways, with subsequent platelet levels in treated patients to determine accurate predictors of the most frequent toxicity, thrombocytopenia. Nine patients with neuroblastoma were given 131I-MIBG (4.9–8.1 GBq or 132–220 mCi) and ten were given 125I-MIBG (8.3-30.0 GBq or 224–809 mCi) as initial treatments. These therapies were sufficiently varied that correlations could be made between indices of the doses and the subsequent toxicity as reflected in circulating platelet levels. Predictors of toxicity were: whole-body absorbed dose of radiation (cGy) calculated from pretherapy tracer doses of 131I-MIBG; GBq/kg of body weight; and GBq/m2 of body surface area. Toxicity was recorded as the nadir of the platelet level and platelet/pretherapeutic level (platelet ratio). For treatments with 131I-MIBG, the highest correlation was obtained between cGy and the logo10-transformed platelet ratio (r=−0.86), but comparison of GBq/m2 and the platelet nadir (r=−0.76) or the platelet ratio (r=−0.74) or the log10 − transformed platelet ratio (r=−0.73) gave comparable and statistically significant results. For treatments with 125I-MIBG, significant correlations were obtained between GBq/m2 and the platelet ratio (r=−0.81) or GBq/kg and the log10 −-transformed platelet ratio; the correlation between cGy and any toxicity index was low. Per administered GBq, 131I-MIBG was 2.6 times more potent than 125I-MIBG in causing a platelet ratio of 0.1. Thus, in predicting toxicity, therapeutic doses of 131I-MIBG expressed as GBq/m2 performed satisfactorily and almost as well as whole-body cGy, and treatment doses of 125I-MIBG expressed as GBq/m2 or GBq/kg performed satisfactorily and much better than whole-body cGy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00182305
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  • 3
    Electronic Resource
    Electronic Resource
    Phaeochromocytoma and functioning paraganglioma in childhood and adolescence: role of iodine 131 metaiodobenzylguanidine (1991)
    Springer
    European journal of nuclear medicine 18 (1991), S. 191-198 
    Details
    ISSN: 1619-7089
    Keywords: Phaeochromocytoma ; Paraganglioma ; childhood ; Adolescence ; Metaiodobenzylguanidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Phaeochromocytomas and functioning paragangliomas are rare tumours in childhood and adolescence. We review our experience of 43 cases (24 men, 19 women) who were first diagnosed at the age of ⩽ 18 years. All patients were evaluated at some point in their illness with iodine 131 metaiodobenzylguanidine (131I-mIBG) scintigraphy. Eight patients (19%) had bilateral adrenal tumours, 12 (28%) had solitary extra-adrenal tumours, and 8 (19%) had multiple tumours. In 10 patients (23%), the tumours were associated with a familial neurocristopathic syndrome. Thirteen of 24 (54%) unifocal tumours which were initially considered to be benign ultimately proved to be multi-focal and/or malignant. The final prevalence of malignancy was 60% − 26 patients, of whom only 15 (57%) had obviously malignant tumours at the time of diagnosis. Primary tumour size ⋝5 cm was more commonly associated with a malignant course in adrenal but not extra-adrenal tumours. No other clinical, biochemical or morphological characteristic was significantly associated with malignancy. Although the high prevalence of malignancy in this series at least partly reflects referral bias, the need for lifelong follow-up of these patients is underscored.131I-mIBG scintigraphy was positive in 36 patients (84%), with a somewhat lower false-negative rate (12%) than X-ray computed tomography (20%). Eight patients with malignant tumours received therapeutic doses of131I-mIBG, with partial tumour responses in 3. Thus,131I-mIBG is an efficacious, non-invasive, localising agent and may be considered as a palliative therapeutic agent when alternatives have failed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262730
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  • 4
    Electronic Resource
    Electronic Resource
    Hexene-1 polymerization by homogeneous zirconocene and heterogeneous-supported TiCl3 catalysts (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1747-1754 
    Details
    ISSN: 0887-624X
    Keywords: zirconocene ; supported TiCl3 ; Ziegler-Natta catalysts ; hexene polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: MgCl2-supported TiCl3 catalysts, with and/or without electron donor modifier (internal Bi or external Be), were compared with rac-ethylenebis(indenyl)zirconium dichloride (1) activated with either MAO or the cation forming agent, triphenyl carbenium tetrakis(pentafluorophenyl)borate (2), with triethylalumium (TEA). The activities of the heterogeneous catalysts depend on the presence or absence of the Lewis base, were relatively insensitive to the temperature of polymerization, and produce poly(hexene) with molecular weights up to 106. The 1/MAO catalyst has about five times higher activity at 50°C but is almost inactive at -30°C; the overall activation energy is 12.4 kcal mol-1. In contrast, the activity for hexene polymerization by the 1/2/TEA catalyst is actually slightly greater at lower temperature. The MW's of poly(hexene) obtained with the zirconocenium catalysts are only in the tens of thousands because of rapid β-hydride elimination by the electrophilic cationic Zr center. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310713
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  • 5
    Electronic Resource
    Electronic Resource
    Polymerization of propylene by zirconocenium catalysts with different counter-ions (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2387-2393 
    Details
    ISSN: 0887-624X
    Keywords: zirconocene ; Ziegler-Natta catalysts ; stereospecific olefin polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Propylene was polymerized by binary zirconocenium catalysts derived from rac-ethylenebis(1-η5-indenyl)dimethylzirconium and cation forming agents (C6H5)3C+(C6F5)4B- and (C6F5)3B. Polymerizations were also performed with the ternary systems of Et[Ind]2ZrCl2, Et3Al, and the cation forming agents. The catalyst systems, with the inert noncoordinating counter-ion, (C6F5)4B-, have much higher activity and stereoselectivity than the ones with the CH3B-(C6F5)3 counter-ion. Much less active still are catalysts having BF4- or (C6H5)4B- counter-ions. Similar but smaller effects of counter-ion structure on ethylene polymerization were observed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321219
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  • 6
    Electronic Resource
    Electronic Resource
    Metallocene catalysts for olefin polymerizations. XXIV. Stereoblock propylene polymerization catalyzed by rac-[anti-ethylidene(1-η5-tetramethylcyclopentadienyl)(1-η5-indenyl)dimethyltitanium: A two-state propagationSee Reference 1. (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2601-2617 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysts ; ansa-metallocene catalyst ; thermoplastic elastomeric poly(propylene) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic-anti-[ethylidene(1-η5-tetramethylcyclopentadienyl) (1-η5-indenyl)dimethyltitanium (6) has been synthesized and its molecular structure determined by x-ray diffraction methods. The two Ti=Me(1) and Ti=Me(2) units have bond distances differing by 0.08 Å and their proton NMR resonances are separated by over 1 ppm. Using this compound and methylaluminoxane (MAO) as the activator, at 25°C the 6/MAO catalyst produced polypropylene having crystalline domain with physical crosslinks. The polymers obtained at lower polymerization temperatures are rheologically liquids. The behaviors of this catalyst system resembles closely the previously reported rac-[anti-ethylidene(1-η5-tetramethylcyclopentadienyl) (1-η5-indenyl)dichlorotitanium (4)/MAO system. The structure of 6 determined here furnishes tangible support for the proposed two-state (isomeric)-switching propagation mechanism. Addition of MAO to 6 causes broadening of the Me(1) resonance in the 1H-NMR spectra, and 6 is decomposed by Ph3C+B(C6F5)-4. © 1992 John Wiley & Sons, Inc.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301215
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