Comparability of Scores From Performance Assessments

Why is comparability of forms important for performance assessments? Can traditional methods of form equating be used? What problems are likely to arise in equating? Can standards generalize across forms?     

Beyond topicality: A two stage view of relevance and the retrieval process

Topicality is an operationally necessary but insufficient condition for requestor judged relevance. Documents are independent of one another as to any judgement of their topicality but not independent as to any judgement of their relevance which is a function of their informativeness to a requestor. Recall depends solely upon topicality but precision depends upon informativeness as well.A retrieval system which aspires to the retrieval of relevant documents should have a second stage which will order the topical set in a manner so as to provide maximum informativeness to the requestor. Should a system be concerned only with topicality then a two stage system which generates a high recall set and discards imprecise documents by measuring their distance from a seed document can be iterated to provide topicality feedback without user input.     

Analysis of a laminar-flow diffusional mixer for directed self-assembly of liposomes

The present work describes the operation and simulation of a microfluidic laminar-flow mixer. Diffusive mixing takes place between a core solution containing lipids in ethanol and a sheath solution containing aqueous buffer, leading to self assembly of liposomes. Present device architecture hydrodynamically focuses the lipid solution into a cylindrical core positioned at the center of a microfluidic channel of 125 × 125-μm² cross-section. Use of the device produces liposomes in the size range of 100–300 nm, with larger liposomes forming at greater ionic strength in the sheath solution and at lower lipid concentration in the core solution. Finite element simulations compute the concentration distributions of solutes at axial distances of greater than 100 channel widths. These simulations reduce computation time and enable computation at long axial distances by utilizing long hexahedral elements in the axial flow region and fine tetrahedral elements in the hydrodynamic focusing region. Present meshing technique is generally useful for simulation of long microfluidic channels and is fully implementable using comsol Multiphysics. Confocal microscopy provides experimental validation of the simulations using fluorescent solutions containing fluorescein or enhanced green fluorescent protein.