Contribution to the theory of photopic vision: Retinal phenomena

Principles of thermodynamics are applied to the study of the ultramicroscopic anatomy of the inner eye. Concepts introduced and discussed include: the retina as a three-dimensional sensor, light signals as coherent beams in relation to the dimensions of retinal pigments, pigment effects topographed by the conjugated antennas effect, visualizing lights, the autotropic function of hemoglobin and some cytochromes, and reversible structural arrangements during photopic adaptation. A paleoecological diagram is presented which traces the evolution of scotopic vision (primitive system) to photopic vision (secondary system) through the emergence of structures sensitive to the intensity, temperature, and wavelengths of the visible range

Optimal Fiscal Policy in Overlapping Generations Models

This paper analyzes the optimal fiscal policy in overlapping generation economies with production where agents live I periods. The primal approach is used to characterize the optimal taxes in steady state and along the transition path to some steady state. The basic idea is to transform the government problem of choosing the optimal taxes, into a simple programming problem of choosing allocations subject to some constraints. The key findings is that if the set of taxes is complete and the utility is homothetic and separable, then capital taxes are zero along the transition path to the steady state after two periods. This result is an equivalent version of Chamley (1986) with overlapping generations. With additional assumptions in the discount factor and endowment of efficiency units, it can be shown that non-separable utility functions satisfy the zero capital taxes result in steady state, but not during the transition path. This is due to the fact that from the government point of view, under this assumptions, the overlapping generation economy is equivalent to an infinitely lived economy.

Roughness evolution of previously milled samples along a polishing test

In the present work results about roughness evolution along a polishing operation with corundum disks of size Norton 400 are presented. Hardened steel and hardened stainless steel samples were previously subjected to ball-end milling or side milling with cylindrical tool at different cutting conditions. Roughness height parameters Ra and Rt, as well as parameters related to the Abbott-Firestone curve such as Rk, Rpk, and Rvk, and shape parameters such as Rsk and Rku were studied. It is usually considered that a polishing operation is complete when Ra does not decrease significantly with more polishing time. In the present paper, an alternative method for determining the end of a polishing test is presented. Roughness is measured both in the longitudinal and in the transversal direction with respect to cutting marks, and it is assumed that the polishing operation is finished when longitudinal values equal transversal values, provided that from that moment on roughness values do not decrease significantly. Moreover, it is recommended to measure parameter Rvk in addition to or even instead of Ra, in order to obtain information about the presence of valleys from the previous milling operation.Postprint (author's final draft

Accretion Disks Around Young Objects. III. Grain Growth

We present detailed models of irradiated T Tauri disks including dust grain growth with power-law size distributions. The models assume complete mixing between dust and gas and solve for the vertical disk structure self-consistentlyincluding the heating effects of stellar irradiation as well as local viscous heating. For a given total dust mass, grain growth is found to decrease the vertical height of the surface where the optical depth to the stellar radiation becomes unit and thus the local irradiation heating, while increasing the disk emission at mm and sub-mm wavelengths. The resulting disk models are less geometrically thick than our previous models assuming interstellar medium dust, and agree better with observed spectral energy distributions and images of edge-on disks, like HK Tau/c and HH 30. The implications of models with grain growth for determining disk masses from long-wavelength emission are considered.Comment: 29 pages, including 11 figures and 1 table, APJ accepte

Financial Innovation, Market Participation and Asset Prices

This paper investigates the pricing effects of financial innovation in an economy with endogenous participation and heterogeneous income risks. The introduction of non-redundant assets endogenously modifies the participation set, reduces the covariance between dividends and participants' consumption and thus leads to lower risk premia. In multisector economies, financial innovation spreads across markets through the diversified portfolio of new entrants, and has rich effects on the cross-section of expected returns. The price changes can also lead some investors to leave the markets and give rise to non-degenerate forms of participation turnover. The model is consistent with several features of financial markets over the past few decades: substantial innovation; higher participation; significant turnover in investor composition; improved risk management practices; a slight increase in interest rates; and a reduction in risk premia.