Latest Dataset Research Articles

Model-independent reconstruction of the expansion history of the Universe and the properties of dark energy

We have improved upon the method of smoothing supernovae data to reconstruct the expansion history of the universe, h(z), using two latest datasets, Gold and SNLS. The reconstruction process does not employ any parameterization and is independent of any dark energy model. The reconstructed h(z) is used to derive the distance factor A up to redshift 0.35 and the results are compared with the given value of A from detection of baryon acoustic oscillation peak (BAO). We find very good agreement between supernovae observations and the results from BAO for \Omega_{0m} \approx 0.276 \pm 0.023. The estimated values of \Omega_{0m} are completely model-independent and are only based on observational data. The derived values of \Omega_{0m} are then used to reconstruct the equation of state of dark energy, w(z). Using our smoothing method we can demonstrate that while SNLS data are in very good agreement with LCDM, the Gold sample slightly prefers evolving dark energy. We also show that proper estimation of the equation of state of dark energy at the high redshifts would be impossible at the current status of observations.

Structural distribution of dipeptides that are identified to be determinants of intracellular protein stability.

The dipeptides that had been previously implicated as determinants of in vivo protein stability (Guruprasad, K., Reddy, B.V.B. and Pandit, M.W., 1990. Protein Eng. 4, 155-161) have been reassessed on a latest data set and about 25% dipeptide combinations (102 dipeptides) were found to play significant role in determining the intracellular protein stability. These were classified as stabilizing dipeptides (Stb), destabilizing dipeptides (Dst) and normal dipeptides (Nor). By different theoretical approaches we have investigated the global localization of these dipeptides in a set of 303 best resolved (< or = 2.0A) non-homologous X-ray defined protein structures. The Dst dipeptides are found to be more of hydrophilic combinations where as Stb dipeptides are more of hydrophobic combinations. We observed a significant difference in overall frequency of occurrence of Stb and Dst dipeptides in different secondary structural regions. The sensitive dipeptides (Stb + Dst) are less in beta-strands and more in coils. A high frequency of occurrence of Stb are observed in the regions closer to the molecular surface compared to the Dst and Nor dipeptides. A significantly high dipole interactions are observed in the Dst dipeptides. The studies indicate that though the Dst dipeptides are more of hydrophilic nature they are localized significantly more in the buried regions of protein structures, on the other hand Stb are more of hydrophobic nature but relatively more accessible to the solvent. These dipeptides therefore increasing sensitivity of the protein to external environment, any alteration in their occurrence in the sequence could increase or decrease intracellular stability of the protein. These observations are useful to select mutations to alter intracellular stability of a given protein and therefore have implications in protein engineering.

Econometric Analysis of Costing System Components in Rail Rate Regulation

In response to Congressional directive, the Interstate Commerce Commission (ICC) has created a railroad costing system that includes as key components ratios designed to estimate variable costs associated with freight transportation. The estimated variability ratios are used to determine freight surcharges, jurisdictional threshold rates, and basic rail rates in administrative law and federal court proceedings. In this article we assess the quality and reliability of the estimated variability ratios and their components against standards from economic theory and statistical theory and practice. Our work includes reproduction of the naive ICC regressions, updated naive regressions for the latest data set, estimation based on more secure econometric foundations, and sensitivity analyses comparing alternative estimation procedures. Fundamental questions arise concerning the scientific and evidentiary standards that are required for econometric methodology in policy making and regulatory activities.