Critical conversion in polymerization processes

2010 ◽  
Vol 79 (10) ◽  
pp. 921-944 ◽  
Author(s):  
T F Irzhak ◽  
Vadim I Irzhak
Keyword(s):  
ChemInform ◽  
2011 ◽  
Vol 42 (14) ◽  
pp. no-no
Author(s):  
T. F. Irzhak ◽  
V. I. Irzhak
Keyword(s):  

2018 ◽  
Vol 25 (4) ◽  
pp. 554-572 ◽  
Author(s):  
Ingrid Wakkee ◽  
Karel Hoestenberghe ◽  
Ernest Mwasalwiba

Purpose The purpose of this paper is to gain insight into the reasons why most Tanzanian graduates do not consider entrepreneurship as an attractive career option despite dire labor market conditions, while a small number of them are able to benefit from local opportunities. Design/methodology/approach Utilizing insights from capability and social capital perspectives, a qualitative investigation based on interviews, group discussions and document analysis was undertaken to explore how this phenomenon can be explained and remedied. Findings This study shows that many graduates value entrepreneurship as a potential career but many find their way to be act upon these aspirations blocked. Indeed, actual entrepreneurial capability is only available to a minority of graduates with access to powerful connections who are able to benefit from technological and financial conversion factors. Most graduates cannot benefit from these conversion factors due to the lack of the necessary social capital to break through to the legal, tax, financial and cultural systems. Hence, the authors argue that social capital itself is actually a critical conversion factor toward developing entrepreneurial capability. Research limitations/implications The insight formulated in this study are based on a qualitative analysis of the Tanzanian context and formulated specifically for this particular context. At the same time, the country shares many characteristics with other countries in Africa, many of which are struggling to move toward a more entrepreneurial society. Hence, the recommendations may partially be transferable beyond the specific Tanzanian situation. Theoretically, the notion that social capital should be considered as a key conversion factor enabling aspiring entrepreneurs in translating valued functionings into actualized functionings and thus toward enhancing entrepreneurial capability opens up novel avenues for empirical research into how entrepreneurship can be stimulated. Social implications This study searches for conversion factors from the actual “functioning” toward the real “capability” allowing to succeed as a new graduate and find that social capital itself might act as the critical conversion factor. That brings the authors to the recommendations for policy makers, educators and media, argued in such a way that the entrepreneurial capability of young graduates and their ability to tap into relevant social capital can be enhanced. Originality/value The combination and integration of the Sen’s capability approach with social capital perspectives offers a novel way to explain difference in responses to the Tanzanian institutions and their ability to act upon a valued functioning such as opportunity-driven entrepreneurship.


1987 ◽  
Vol 65 (10) ◽  
pp. 2447-2449 ◽  
Author(s):  
Xingpei Zhu ◽  
Etchri Amouzou ◽  
Stewart McLean

Petromyzonol, a rare bile substance, has been prepared from an abundant starting material, cholic acid. The critical conversion, the inversion of the configuration at C-5, was accomplished by oxidizing a suitably protected derivative of cholic acid to a 1,4-dien-3-one, which was then stereoselectively reduced to methyl allocholate. In a single oxidation step, the 3-hydroxy steroid was converted to the dienone by Barton's procedure using a catalytic amount of benzeneseleninic anhydride and m-iodoxybenzoic acid as the stoichiometric oxidant. The stereoselective reduction employed two steps: hydrogenation of the dienone to the saturated ketone (5α) in the presence of the Wilkinson catalyst, followed by reduction of the ketone with K-Selectride. Finally, methyl allocholate was reduced to petromyzonol with lithium aluminum hydride.


e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Tamara F. Irzhak ◽  
Vadim I. Irzhak

AbstractRelations between the critical conversion of gelation αc and the conditions of polymer formation by living and terminated polymerization were studied. It was shown that the weight average functionality of the initial system given by the formula,Φ22(0)=∑ i(i-1)mi where mi is the initial concentration of an i-functional monomer, is the parameter determining the value of αc. Formulas relating the critical conversion to the kinetic parameters of polymerization processes are presented. For polycondensation processes the kinetic equation based on the concept of bond blocks is proposed. It allows for estimating the gel point even for systems in which the substitution effect takes place for one of the components. The equation α ∑ i(i-1)ni=1 is , where α is the current conversion and ni are the values specifying the concentrations of i-functional blocks. The latter values are functions of α and may be calculated kinetically.


Author(s):  
T. R. Deberdeev ◽  
V. I. Irzhak ◽  
R. Ya. Deberdeev ◽  
O. V. Stoynov
Keyword(s):  

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