166,550 research outputs found
From open resources to educational opportunity
Since MITâs bold announcement of the OpenCourseWare initiative in 2001, the content of over 700 of its courses have been published on the Web and made available for free to the world. Important infrastructure initiatives have also been launched recently with a view to enabling the sustainable implementation of these educational programmes, through strengthening organizational capacity as well as through building open, standardsâbased technology. Each of these initiatives point to a rich palette of transformational possibilities for education; together with the growing open source movement, they offer glimpses of a sustainable ecology of substantial and quality educational resources. This discussion piece will highlight some of the educational opportunity presented by MITâs current information technologyâenabled educational agenda and related initiatives, along with their strategic underpinnings and implications. It will address various dimensions of their impact on the form and function of education. It will examine how these ambitious programmes achieve a vision characterized by an abundance of sustainable, transformative educational opportunities, not merely pervasive technology
Origin of translocation barriers for polyelectrolyte chains
For single-file translocations of a charged macromolecule through a narrow
pore, the crucial step of arrival of an end at the pore suffers from free
energy barriers, arising from changes in intrachain electrostatic interaction,
distribution of ionic clouds and solvent molecules, and conformational entropy
of the chain. All contributing factors to the barrier in the initial stage of
translocation are evaluated by using the self-consistent field theory for the
polyelectrolyte and the coupled Poisson-Boltzmann description for ions, without
radial symmetry. The barrier is found to be essentially entropic, due to
conformational changes. For moderate and high salt concentrations, the barriers
for the polyelectrolyte chain are quantitatively equivalent to that of
uncharged self-avoiding walks. Electrostatic effects are shown to increase the
free energy barriers, but only slightly. The degree of ionization,
electrostatic interaction strength, decreasing salt concentration and the
solvent quality all result in increases in the barrier.Comment: J.Chem. Phys. 131, 21 (2009) - to be appeare
- âŠ