Markovian Description of Unbiased Polymer Translocation

We perform, with the help of cloud computing resources, extensive Langevin simulations which provide compelling evidence in favor of a general markovian framework for unbiased polymer translocation. Our statistical analysis consists of careful evaluations of (i) two-point correlation functions of the translocation coordinate and (ii) the empirical probabilities of complete polymer translocation (taken as a function of the initial number of monomers on a given side of the membrane). We find good agreement with predictions derived from the Markov chain approach recently addressed in the literature by the present authors.Comment: 11 pages, 4 figure

Coulomb and nuclear effects in breakup and reaction cross sections

We use a three-body Continuum Discretized Coupled Channel (CDCC) model to investigate Coulomb and nuclear effects in breakup and reaction cross sections. The breakup of the projectile is simulated by a finite number of square integrable wave functions. First we show that the scattering matrices can be split in a nuclear term, and in a Coulomb term. This decomposition is based on the Lippmann-Schwinger equation, and requires the scattering wave functions. We present two different methods to separate both effects. Then, we apply this separation to breakup and reaction cross sections of 7Li + 208Pb. For breakup, we investigate various aspects, such as the role of the alpha + t continuum, the angular-momentum distribution, and the balance between Coulomb and nuclear effects. We show that there is a large ambiguity in defining the 'Coulomb' and 'nuclear' breakup cross sections, since both techniques, although providing the same total breakup cross sections, strongly differ for the individual components. We suggest a third method which could be efficiently used to address convergence problems at large angular momentum. For reaction cross sections, interference effects are smaller, and the nuclear contribution is dominant above the Coulomb barrier. We also draw attention on different definitions of the reaction cross section which exist in the literature, and which may induce small, but significant, differences in the numerical values.Comment: 12 pages, 11 figure

ON THE RENTAL PRICE OF CAPITAL AND THE PROFIT RATE: THE PERILS AND PITFALLS OF TOTAL FACTOR PRODUCTIVITY GROWTH

This paper considers the implications of the conceptual difference between the rental price of capital, embedded in the neoclassical cost identity (output equals the cost of labour plus the cost of capital), and used in growth accounting studies; and the profit rate, which can be derived from the national income and product accounts (NIPA). The neoclassical identity is a "virtual" identity in that it depends on a series of assumptions (constant returns to scale and perfectly competitive factor markets). The income side of the NIPA also provides an accounting identity for output as the sum of the wage bill plus the surplus. This identity, however, is a "real" one, in the sense that it does not depend on any assumptions and thus it holds always. It is shown that because the neoclassical cost identity and the income accounting identity according to the NIPA are formally equivalent expressions, estimations of aggregate production functions and growth accounting studies are tautologies. Likewise, the test of the hypothesis of competitive markets using Hall's (1988) framework gives rise to a null hypothesis that cannot be rejected statistically.

The use and misuse of computers in education : evidence from a randomized experiment in Colombia

This paper presents the evaluation of the program Computers for Education. The program aims to integrate computers, donated by the private sector, into the teaching of language in public schools. The authors conduct a two-year randomized evaluation of the program using a sample of 97 schools and 5,201 children. Overall, the program seems to have had little effect on students'test scores and other outcomes. These results are consistent across grade levels, subjects, and gender. The main reason for these results seems to be the failure to incorporate the computers into the educational process. Although the program increased the number of computers in the treatment schools and provided training to the teachers on how to use the computers in their classrooms, surveys of both teachers and students suggest that teachers did not incorporate the computers into their curriculum.Tertiary Education,Primary Education,Secondary Education,Teaching and Learning,Education For All