bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanistic implications of the end group structure in radical telechelic polybutadienes as studied by NMR
Authors: Bresler Lubov' S. , Barantsevich Eugene N. , Polyansky Victor I. , Ivantchev Sergey S. 
Published: April 2003

Abstract270 MHz 1H NMR spectra were used to study of the structure of end groups and terminal monomeric units in polybutadienes produced by radical polymerization, initiated with hydrogen peroxide and a series of substituted benzoyl peroxides. The hydroxyl or aroyl groups were found to be bounded to the methylene end group of the 1,4‐cis‐, 1,4‐trans‐ or 1,2‐butadiene terminal units. The terminal units are richer in 1,2‐structures than the backbone due to the influence of hydroxyle or of the groups on the relative reactivity of carbons 1 and 3 in the allylic radical, formed by initiation. 1,2‐Units at the chain ends and in the backbone are predominantly joined to 1,4‐units; this results in a magnetic nonequivalence of the methylene protons in 1,2‐structures. Data are also presented on the extent of radical decarboxylation during initiation by substituted benzoyl peroxides and also on the introduction of solvent fragements in polybutadienes obtained by initiation with hydrogen peroxide in alcoholic media.
Refractive index increments of polyacrylamide and comments on the light scattering from its solutions
Authors: Stejskal Jaroslav , Horská Jitka 
Published: April 2003

AbstractThe refractive index increments of polyacrylamide for various wavelength were determined both in the usual solvents (water, ethylene glycol, formamide) and in those so far unused (ethanolamine, dimethyl sulfoxide). The values thus obtained are compared with the reported data. The necessity to employ anhydrous polyacrylamide samples is stressed. The question of the possible effects of ageing of solutions on the refractive index increment values is discussed. No ageing of solutions was observed at room temperature; at elevated temperatures, the amide groups of the polymer undergo hydrolysis in water.
Configurational chracteristics of the polysulfides, 3. Dipole moments of poly(trimethylene sulfide) and comparisons between some polysulfides and the corresponding polyoxides
Authors: Guzman J. , Riande E. , Welsh W. J. , Mark J. E. 
Published: April 2003

AbstractConformational energy calculations indicate that poly(trimethylene sulfide) (P3MS) approximates the idealized freely‐rotating chain in that gauche‐trans energy differences in this molecule are very small. This occurs because the relatively long SC bond tends to relieve congestion within the P3MS chain. The bonds in poly(trimethylene oxide) (P3MO) are much more constrained to a particular rotational state because the OC bond is shorter than the SC one, and in this sense P3MO is considerably less flexible. In this study the dipole moments 〈μ2〉0 of P3MS are measured as a function of temperature, and the results analyzed in terms of the rotational isomeric‐state theory. Using conformational energies derived from semiempirical potential energy functions, a three‐rotational‐state model gave values of the dipole moment in good agreement with experiment. Theoretical and experimental values of the temperature coefficient of 〈μ2〉0 were in disagreement, however, and a five‐rotational‐state model based on that adopted by Flory in a similar study of polymethylene failed to remove this discrepancy. Some statistical properties are tabulated for the n‐alkylene polysulfides studied to date and for structurally related polyoxides. In these types of molecules, strong preferences for pairs of gauche states in CH2SCH2SCH2 and CH2 OCH2OCH2 sequences give rise to unusually small values of the dipole moment.
A statistical analysis for stereo‐configurational sequences of vinyl polymers
Authors: Yan Deyue 
Published: April 2003

AbstractIn this paper, the distribution of configurational sequences in vinyl polymers is re‐treated theoretically by the aid of statistics. Various Markovian probabilities of multi‐ads are listed. A series of relationships among the frequencies of occurrence of n‐ads with different configurations is obtained, most of them have not been reported up to now. Finally, a convenient method for determination of the order of a Markovian process is established.
Unvernetzte epoxid‐amin‐additionspolymere, 6. DSC‐untersuchungen zur kinetik der stufenadditionspolymerisation von 2,2‐bis[4‐(2,3‐epoxypropoxy) phenyl] propan mit N,N′‐dibenzylethylendiamin und benzylamin
Authors: Flammersheim Hans‐Jürgen , Hörhold Hans‐Heinrich , Bellstedt Klaus , Klee Joachim 
Published: April 2003

AbstractThe kinetics of the linear step‐growth addition polymerization of equimolar amounts of the diglycidyl ether of bisphenol‐A 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane (1) with N,N′‐dibenzylethylenediamine (2) and with benzylamine (4), respectively, is studied by means of differential scanning calorimetry (DSC). For conversions α ≤ 0,90 the experimental results of the isothermic measurements are in excellent agreement with values calculated from the rate equation dα/dt = (k1 + k2 αm) (1 − α)n with m + n = 2,5 (m ≈︁ 1,0, n ≈︁ 1,5). The first term of this rate equation takes into account both the catalytic and autocatalytic character of the addition polymerization while the exponent n ≈︁ 1,5 in the second term shows that the effective concentration of one of the addition components is given by the square root of its concentration.
Interaction between dyes and polyelectrolytes, 14. Triplet energy transfer in a cationic dye‐polyanion system
Authors: Shirai Masamitsu , Ono Yoshiki , Tanaka Makoto 
Published: April 2003

AbstractPolymers with different fractions of azobenzene residues were prepared by radical copolymerization of methacrylic acid with 4′‐phenylazomethacrylanilid. The triplet excitation energy transfer from methylene blue (1) to the azobenzene residues in the polymers was investigated by using the 1‐photosensitized cis → trans isomerization of the azobenzene residue. The efficiency of the triplet excitation energy transfer from 1 to 4‐(4′‐phenylazoanilinocarbonyl)butanoic acid (4) as a monomer model compound. The number of azobenzene residues per polymer molecule and the molecular weight of the polymer were important factors for the efficient triplet excitation energy transfer. On addition of NaCl the energy transfer efficiency was lowered, suggesting that the binding of 1 to the polymer by electrostatic forces plays an important role. Binding of 1 to the polymers was investigated spectrophotometrically. Correlation with the binding of 1 to the polymers and the efficiency of triplet excitation energy transfer between 1 and azobenzene residues in the polymers is discussed.
Preparation of regularly sequenced polyamides with definite numbers of oxyethylene units and their application as phase transfer catalysts
Authors: Iwabuchi Susumu , Nakahira Takayuki , Tsuchiya Atsushi , Kojima Kuniharu , Böhmer Volker 
Published: April 2003

AbstractPolyamides (1–3) having oligo(oxyethylene) segments in the main chain were prepared from α‐(2‐aminoethyl)‐ω‐aminooligo(oxyethylene)s (4) and dicarboxylic acid chlorides (5). Their ability to form complexes with alkali metal ions was examined by the picrate extraction method. The polyamides were found to catalyze the nucleophilic displacement reaction of hexyl bromide by potassium acetate in acetonitrile. An intramolecular co‐operative action of oligo(oxy‐ethylene) segments in complexation of potassium ion is proposed to account for the observed “polymer effect” in the catalytic activity.
Pharmacologically active polymers, 23. Linear and branched zwitterionic derivatives of polyethyleneimine as carriers for pharmacologically active components
Authors: Kobayashi Shiro , Gros Leo , Muacevic Gojko , Ringsdorf Helmut 
Published: April 2003

AbstractTo obtain a carrier polymer for pharmacologically active components, linear polyethyleneimine (LPEI) was chemically modified by reactions with acrylic acid (1a), acrylamide (1b), acrylic acid esters (1c and 1d), sodium chloroacetate, and hydrochloric acid. All product polymers 2a – 2e are soluble in water. Among these, 2a and 2e, β‐ and α‐amino acid derivatives, respectively, show no acute toxicity in mice up to dosages of 1 g/kg i. v. Similar types of polymers 5a and 5b and a polymer containing phosphonic acid moieties (5d) derived from branched polyethyleneimine (BPEI) were prepared. 5a and 5b are also nontoxic regardless of the molecular weight of four kinds of BPEI and of the wide range of carboxylic group content in the polymer. It is suggested that the zwitterion form contributes to the nontoxic nature of β‐and α‐amino acid type polymers. The present results show that amino acid type polymers derived from LPEI and BPEI can be used as carrier polymers for pharmacologically active components.
Untersuchung der teilschritte der ethylen‐hochdruckpolymerisation, 2. Druck‐ und temperaturabhängigkeit der einzelnen geschwindigkeitskonstanten
Authors: Lim Pe‐Chin , Luft Gerhard 
Published: April 2003

AbstractIn the first part of this series the individual rate constants of the radical polymerization of ethylene are reported in dependency of pressure at 405 K. By further measurements under 500 – 1750 bar and 400 – 470 K, using again the method of the rotating sector, the dependency of the rate constants on both pressure and temperature was determined. With increasing temperature the rate constant of chain growth kp as well as that of chain termination kt increases. With increasing pressure, kp increases, whereas kt decreases because of the diffusion controlled termination reaction. For the chain growth an activation energy of Ep = 37 kJ/mol and an activiation volume of Δvp≠ = ‐25,5 ml/mol was found. The activiation parameters of the chain termination are Et = 9,9 kJ/mol and Δvt≠ = 7 ml/mol. Based on these results and literature data the rate constants of different chain transfer reactions involved in the high pressure polymerization of ethylene and their dependency on temperature and pressure were evaluated.
Free radical polymerization of water‐soluble vinyl monomers in the two‐phase (water/organic) system using methylated β‐cyclodextrins as initiator‐carriers
Authors: Taguchi Hiromu , Kunieda Norio , Kinoshita Masayoshi 
Published: April 2003

AbstractIn the polymerization of water‐soluble vinyl monomers, such as acrylamide, sodium p‐sty‐renesulfonate, acrylic acid, and methacrylic acid, using water‐insoluble free radical initiators such as azo or peroxide compounds in the two‐phase system consisting of water and an organic solvent (chloroform/ligroin, volume ratio 1:4), the addition of a small amount of a methylated β‐cyclodextrin, heptakis(2,6‐O‐dimethyl)‐β‐cyclodextrin (DM‐β‐CD) or heptakis(2,3,6‐O‐trimethyl)‐β‐cyclodextrin (TM‐β‐CD), was found to cause a marked increase in conversion of the polymerization. Based on this finding, it may be suggested that the methylated β‐cyclodextrins act as initiator‐carriers which transport the water‐insoluble initiators from the organic phase to the aqueous phase to initiate the polymerization of water‐soluble vinyl monomers.
Preparation and properties of poly(p‐phenylene) and polynaphthylene
Authors: Sato Masa‐aki , Kaeriyama Kyoji , Someno Kazuo 
Published: April 2003

AbstractPoly(p‐phenylene), poly(2,6‐naphthylene), poly(2,7‐naphthylene), poly(1,5‐naphthylene), and poly(1,4‐naphthylene) were prepared by nickel‐catalyzed polycondensation of Grignard reagents from the corresponding dibromides. The polymers were annealed in vacuo. Doping with SbF5 markedly increase the conductivity of the polymers. Annealed poly(2,6‐naphthylene) is the most conductive among the four isomers after SbF5 doping. The conductivity of doped poly(2,6‐naphthylene) and poly(p‐phenylene) is about 10−1 S · cm−1. Annealed poly(p‐phenylene) shows a broad single line ESR signal which changes to a narrow single line upon doping. Superposition of the two signals is observed at the initial stage of doping. Simultaneous conductivity and ESR measurements indicate that the narrow signal is closely related to conductivity.
Furan and pyran derivatives as modifiers of propylene polymerization catalysts
Authors: Karayannis Nicholas M. , Lee Sam S. 
Published: April 2003

AbstractStudies of various tetrahydrofuran and tetrahydropyran derivatives as modifiers of Zieglertype propylene polymerization catalysts are reported. Among methyl derivatives, ethers containing two methyl substituents on carbon atoms adjacent to the etheric oxygen provied the best activity‐stereospecificity combinations (e.g. 2,5‐dimethyltetrahydrofuran (1c) and 2,2,4,4‐tetramethyltetrahydrofuran) (4). Significantly better stereospecificity with some loss in activity is realized when bulkier ethers such as isochroman (5) or 2‐(tetrahydrofurfuryloxy)tetrahydropyran (6) are used. On the other hand, combination of one of the preceding ethers with a second modifier (bis(tributyltin) sulfide, tributyl phosphite, or triethyl thiosphosphate) results in catalyst systems characterized by very attractive activity‐stereospecificity combinations. Systems of this type, containing 1c or 4, exhibit higher activity and about equal or better stereospecificity than the systems modified only with the second modifier; whereas 5 and 6 depress somewhat the activity of the latter systems but provide substantially improved stereospecificity. The steric and electronic effects introduced by the ether modifiers in the single and binary modifier systems investigated are discussed.
Synthesis of poly(ethylene‐d4oxide) with unimodal and narrow molecular weight distribution
Authors: Eisenbach Claus D. , Peuscher Manfred , Wegner Gerhard , Weiss Monika 
Published: April 2003

AbstractPoly(ethylene‐d4 oxide) in the molecular weight range 104 to 105 has been synthesized by anionic polymerization of highly pure ethylene‐d4 oxide with carbazolylpotassium as initiator in the presence of a cryptand in THF as solvent. The polymers show an unimodal molecular weight distribution as confirmed by high pressure liquid chromatography and a polydispersity between 0,2 and 0,5.
Structure and properties of segmented poly(ether‐ester)s, 7. Model triblock copolyesters of monodisperse block length
Authors: Schmidt Friedrich Gerog , Dröscher Michael 
Published: April 2003

AbstractSynthesis and characterization of model triblock copolyesters, in which the two end‐blocks are based on tetramethylene terephthalate and the middle block is oligo(oxytetramethylene), are described. These model copolyesters, which are essentially monodisperse, and similarly prepared segmented block copolyesters with monodisperse blocks exhibit the same dependency of the melting temperature on the degree of polymerization of the ester blocks as polydisperse technical copoly(ether‐ester)s.
Dual Chamber Pacing in Hypertrophic Cardiomyopathy: Influence of Atrioventricular Delay on Left Ventricular Outflow Tract Obstruction
Authors: Losi Maria-Angela , Betocchi Sandro , Briguori Carlo , Piscione Federico , Manganelli Fiore , Ciampi Quirino , Stabile Giuseppe , Chiariello Massimo 
Published: April 2003

The impact of the duration of atrioventricular (AV) delay on obstruction in hypertrophic cardiomyopathy was evaluated in 12 patients by cardiac catheterization, and in 8 of them also by Doppler echocardiography. The AV delay was programmed in random order at 125, 100 and 75 ms in the invasive study and at 120, 100 and 80 ms after pacemaker implantation. The arterial pressure did not changed throughout the studies, whereas the gradient decreased significantly by reducing the AV delay value; the greater gradient reduction was obtained, in both studies, with the AV delay set between 75 or 80 and 100 ms. QRS duration increased significantly by reducing the AV delay during both studies. The widest QRS was not associated with the smallest gradient in all patients. Changes in gradients were similar during the invasive and noninvasive protocols.
Outflow Acceleration Assessed by Continuous-Wave Doppler Echocardiography in Left Ventricular Hypertrophy: An Analysis of 103 Consecutive Cases
Authors: Faber L. , Heemann A. , Sürig M. , Michalowski Z. , Gleichmann U. , Klempt H.W. 
Published: April 2003

The effect of provocation on left ventricular (LV) outflow was studied by continuous-wave Doppler echocardiography in 103 nonselected, consecutively enrolled patients with LV hypertrophy (LVH), either due to pressure overload (97 patients) or hypertrophic cardiomyopathy (HCM, 6 patients). In 34 patients with LVH, outflow acceleration (gradients ranging from 18 to 122 mm Hg) was induced or accentuated by the Valsalva maneuver after 1.6 mg nitroglycerine sublingually independent of LVH etiology. Factors associated with LV outflow acceleration were female sex, small body surface area and LV cavity size, increased relative wall thickness, LV contractility, and resting LV outflow velocity, mitral anulus calcifications and systolic anterior movement of the mitral valve. It is concluded that dynamic, intracavity LV gradients are a nonspecific flow abnormality that merit consideration because they can be frequently found in LVH patients.
Specificity of Cardiac Troponin I and Creatine Kinase-MB Isoenzyme in Asymptomatic Long-Term Hemodialysis Patients and Effect of Hemodialysis on These Cardiac Markers
Authors: Tun Aung , Khan IjazA. , Win MoeT. , Hussain Akhtar , Hla TinA. , Wattanasuwan Narrapol , Vasavada BalenduC. , Sacchi TerrenceJ. 
Published: April 2003

<b>Objectives:</b> The objectives of this study were: (1) to evaluate the specificity of cardiac troponin I and creatine kinase-MB isoenzyme in ambulatory asymptomatic chronic renal failure patients on long-term hemodialysis, and (2) to evaluate the effect of hemodialysis on the serum levels of cardiac troponin I and creatine kinase-MB isoenzyme. <b>Methods:</b> One hundred and forty-four consecutive ambulatory asymptomatic chronic renal failure patients on hemodialysis for a minimum of 1 year were evaluated clinically. Serum cardiac troponin I and creatine kinase-MB isoenzyme levels were measured with specific monoclonal antibodies before and after dialysis using ACCESS Troponin I and ACCESS CK-MB assays. <b>Results:</b> The specificity of serum cardiac troponin I was 83% with a cutoff level of 0.03 ng/ml, which is an expected level for healthy population, but it rose to 100% with a cutoff level of 0.15 ng/ml, which is a reference level for patients with acute myocardial infarction. Twenty-four (17%) patients had borderline elevation in cardiac troponin I (>0.03 to <0.15 ng/ml). A history of angina pectoris was more common in the borderline-elevated cardiac troponin I subgroup. In 28% of the patients, serum creatine kinase-MB isoenzyme levels were increased with a specificity of 72% at a cutoff level of 4 ng/ml, which is the upper limit of normal, but the specificity rose to 98% by increasing the cutoff level value to 10 ng/ml. There were no statistically significant differences in serum levels of cardiac troponin I and creatine kinase-MB isoenzyme before and after dialysis. <b>Conclusions:</b> Cardiac troponin I is highly specific in ambulatory asymptomatic chronic renal failure patients on long-term hemodialysis; borderline elevations in cardiac troponin I may represent microinjury to the myocardium. A serum level of creatine kinase-MB isoenzyme >2.5 times of the normal upper limit may be highly specific in this patient population. Hemodialysis per se does not significantly change the serum levels of cardiac troponin I and creatine kinase-MB isoenzyme.
Nonischemic End-Systolic Performance
Authors: Meyer Theo E. , Perlini Stefano , Foëx Pierre 
Published: April 2003

Nonischemic end-systolic performance decreases during ischemia. These changes in performance are likely to be dependent on the size and site of the ischemic zone, as well as the prevailing loading conditions. This study was designed to examine the effect of regional and generalized changes in inotropy on nonischemic end-systolic performance, independent of the ischemic zone size. Twenty dogs were instrumented with sonomicrometers and micromanometer pressure gauges. End-systolic pressure-thickness relationship data were obained during vena-caval balloon inflation. Measurements were obtained before and 90 s after left circumflex (LC) artery occlusion. Then, simultaneous with the occlusion of the LC artery, isoproterenol (0.04 μg/ml) was infused into the left anterior descending artery. After recovery, the same protocol was repeated before and after propranolol (0.5 mg/kg). In a separate set of animals, the same measurements were made following 2.5 and 5 μg/kg/min dobutamine. The effect of ischemia on the nonischemic end-systolic pressure-thickness relationship was expressed as the extent to which the relationship is shifted to the left. Infusion of intracoronary isoproterenol into the perfusion bed of the nonischemic zone produced a significant increase in the slope of the end-systolic pressure-thickness relationship. During ischemia, however, the extent of leftward shift of this relationship was less than that following β-blockade. Intravenous dobutamine resulted in a dose-dependent increase in the slope of the nonischemic end-systolic pressure thickness relationship, but the extent of leftward displacement of the relationship in response to regional ischemia was less than that following the control occlusion. The nonischemic segment is coupled with the nonfunctioning ischemic zone in such a way that it is required of the nonischemic segment to operate at decreased end-systolic thickness for any end-systolic pressure, the extent of which is to be determined, in part, by the size of the ischemic zone and the contractile state of the nonischemic myocardium. The lower the contractile state prior to coronary occlusion the greater extent of leftward shift of the pressure-thickness relationship.
Dispersion of QT Interval following Ventricular Premature Beats and Mortality after Myocardial Infarction
Authors: Dabrowski Andrzej , Kramarz Elżbieta , Piotrowicz Ryszard 
Published: April 2003

In a group of 193 postinfarction patients with ventricular premature beats on a resting 12-lead ECG, the dispersion of QT and JT intervals was calculated as a difference between maximum and minimum QT and JT intervals in ventricular premature beats. During a follow-up of 38 ± 17 months, death from all causes was noted in 56 patients. Univariate predictors of mortality included QT dispersion ≥100 ms, JT dispersion ≥100 ms, left ventricular ejection fraction <40%, complete bundle branch block, ‘R-on-T’ index of ventricular premature beats <1 and age of patients >60 years. At multivariate Cox proportional hazards survival analysis, only QT dispersion ≥100 ms, left ventricular ejection fraction <40% and complete bundle branch block had an independent relation to postinfarction mortality. The final model selected increased QT dispersion as the prognostic factor which was the most strongly related to mortality (χ<sup>2</sup> = 23.60, p = 0.0000).