Note on the physical basis of spatially resolved thermodynamic functions

The spatial resolution of thermodynamic functions, exemplified by the entropy, is discussed. A physical definition of the spatial resolution based on a spatial analogy of the partial molar entropy is advocated. It is shown that neither the grid cell theory (Gerogiokas et al., J. Chem. Theory Comput., 10, 35 [2014]), nor the first-order grid inhomogeneous solvation theory (Nguyen et al. J. Chem. Phys., 137, 044101 [2012]), of spatially resolved hydration entropies satisfies the definition.Comment: Essentially 2 double-column pages, no figure

Modification of the Gay-Berne potential for improved accuracy and speed

A modification of the Gay-Berne potential is proposed which is about 10% to 20% more speed efficient (that is, the original potential runs 15% to 25% slower, depending on architecture) and statistically more accurate in reproducing the energy of interaction of two linear Lennard-Jones tetratomics when averaged over all orientations. For the special cases of end-to-end and side-by-side configurations, the new potential is equivalent to the Gay-Berne one.Comment: 5 pages (incl. title page), [preprint,aip,jcp]{RevTEX-4.1}, 1 figure, 1 table. Revised version fixes mathematical typos and adds short paragraph on a natural generalization to dissimilar particle

Gaussian-Charge Polarizable Interaction Potential for Carbon Dioxide

A number of simple pair interaction potentials of the carbon dioxide molecule are investigated and found to underestimate the magnitude of the second virial coefficient in the temperature interval 220 K to 448 K by up to 20%. Also the third virial coefficient is underestimated by these models. A rigid, polarizable, three-site interaction potential reproduces the experimental second and third virial coefficients to within a few percent. It is based on the modified Buckingham exp-6 potential, an anisotropic Axilrod-Teller correction and Gaussian charge densities on the atomic sites with an inducible dipole at the center of mass. The electric quadrupole moment, polarizability and bond distances are set to equal experiment. Density of the fluid at 200 and 800 bars pressure is reproduced to within some percent of observation over the temperature range 250 K to 310 K. The dimer structure is in passable agreement with electronically resolved quantum-mechanical calculations in the literature, as are those of the monohydrated monomer and dimer complexes using the polarizable GCPM water potential. Qualitative agreement with experiment is also obtained, when quantum corrections are included, for the relative stability of the trimer conformations, which is not the case for the pair potentials.Comment: Error in the long-range correction fixed and three-body dispersion introduced. 32 pages (incl. title page), 7 figures, 9 tables, double-space

Fluorescent Discrimination between Traces of Chemical Warfare Agents and Their Mimics

An array of fluorogenic probes is able to discriminate between nerve agents, sarin, soman, tabun, VX and their mimics, in water or organic solvent, by qualitative fluorescence patterns and quantitative multivariate analysis, thus making the system suitable for the inthe- field detection of traces of chemical warfare agents as well as to differentiate between the real nerve agents and other related compounds.Ministerio de Economía y Competitividad, Spain (Project CTQ2012- 31611), Junta de Castilla y León, Consejería de Educación y Cultura y Fondo Social Europeo (Project BU246A12-1), the European Commission, Seventh Framework Programme (Project SNIFFER FP7-SEC-2012-312411) and the Swedish Ministry of Defence (no. A403913

Theoretical evaluation of partial credit scoring of the multiple-response test item

We compute and compare statistics of five different scoring rules for the selected-response type of test items where the number of keys is an arbitrary integer and the test-takers are perfectly rational agents. We consider a hypothetical test of factual recognition, in which the underlying ability that we seek to measure is the fraction of the item options that the test-taker truly recognizes (and not only guesses correctly), assumed directly proportional the test-taker’s domain knowledge

Multiple-choice test items with "none of the above" as an alternative

We analyze idealized multiple-choice tests and examine the effects when some or all of the items are modified so as to include “none of the above” as an answer option. As regards this modification, we study item difficulty, discrimination, and reliability, both for scoring rules that suppress guessing and those that encourage it. We also briefly consider the influence of test-taker misinformation. In agreement with virtually all published empirical findings, we show that the variant formats are more difficult than the content-equivalent regular items, albeit for the variant format where “none of the above” is the correct alternative, a predicted, apparent selection effect mitigates this increase through guessing. As regards item discrimination, it is greater for the regular item format for tests with mixed formats, save for those tests where the regular item format is in minority. This explains the confusion in the empirical literature in this regard