122 research outputs found
Optimal Taxation and Social Insurance in a Lifetime Perspective
Advances in information technology have improved the administrative feasibility of redis- tribution based on lifetime earnings recorded at the time of retirement. We study optimal lifetime income taxation and social insurance in an economy in which redistributive taxation and social insurance serve to insure (ex ante) against skill heterogeneity as well as disability risk. Optimal disability benefits rise with previous earnings so that public transfers depend not only on current earnings but also on earnings in the past. Hence, lifetime taxation rather than annual taxation is optimal. The optimal tax-transfer system does not provide full disability insurance. By offering imperfect insurance and structuring disability benefits so as to enable workers to insure against disability by working harder, social insurance is designed to offset the distortionary impact of the redistributive labor income tax on labor supply.Optimal lifetime income taxation;optimal social insurance
Individual savings accounts for social insurance:Rationale and alternative designs
Using Danish data, we find that about three-fourths of the taxes levied to finance public transfers actually finance benefits that redistribute income over the life cycle of individual taxpayers rather than redistribute resources across people. This finding and similar results for other countries provide a rationale for financing part of social insurance via mandatory individual savings accounts. We discuss the advantages and disadvantages of mandatory individual savings accounts for social insurance and survey some recent alternative proposals for such accounts
Optimized arrays for 2-D resistivity survey lines with a large number of electrodes
Previous studies show that optimized arrays generated using the âCompare Râ method have significantly better resolution than conventional arrays. This method determines the optimum set of arrays by selecting those that give the maximum model resolution. The number of possible arrays (the comprehensive data set) increases with the fourth power of the number of electrodes. The optimization method faces practical limitations for 2-D survey lines with more than 60 electrodes where the number of possible arrays exceeds a million. Several techniques are proposed to reduce the calculation time for such survey lines. A single-precision version of the âCompare Râ algorithm using a new ranking function reduces the calculation time by two to eight times while providing results similar to the double-precision version. Recent improvements in computer GPU technology can reduce the calculation time by about seven times. The calculation time is reduced by half by using the fact that arrays that are symmetrical about the center of the line produce identical changes in the model resolution
values. It is further reduced by more than thirty times by calculating the ShermanâMorrison update for all the possible two-electrode combinations, which are then used to calculate the model resolution values for the four-electrode arrays. The calculation time is reduced by more then ten times by using a subset of the comprehensive
data set consisting of only symmetrical arrays. Tests with a synthetic model and field data set show that optimized arrays derived from this subset produce inversion models with differences of less than 10% from those derived using the full comprehensive data set. The optimized data sets produced models that are more accurate than the WennerâSchlumberger array data sets in all the tests
On the Application of the Non Linear Sigma Model to Spin Chains and Spin Ladders
We review the non linear sigma model approach (NLSM) to spin chains and spin
ladders, presenting new results. The generalization of the Haldane's map to
ladders in the Hamiltonian approach, give rise to different values of the
parameter depending on the spin S, the number of legs and
the choice of blocks needed to built up the NLSM fields. For rectangular blocks
we obtain or depending on wether , is even or
odd, while for diagonal blocks we obtain . Both
results agree modulo , and yield the same prediction, namely that even (
resp. odd) ladders are gapped (resp. gapless). For even legged ladders we show
that the spin gap collapses exponentially with and we propose a
finite size correction to the gap formula recently derived by Chakravarty using
the 2+1 NSLM, which gives a good fit of numerical results. We show the
existence of a Haldane phase in the two legged ladder using diagonal blocks and
finally we consider the phase diagram of dimerized ladders.Comment: 25 pages, Latex, 7 figures in postscript files, Proc. of the 1996 El
Escorial Summer School on "Strongly Correlated Magnetic and Superconducting
Systems". Some more references are adde
Validation of standard and alternative satellite ocean-color chlorophyll products off Western Iberia
Chlorophyll a concentration (Chl) product validation off theWestern Iberian coast is here undertaken by directly
comparing remote sensing data with in situ surface reference values. Both standard and recently developed
alternative algorithms are considered for match-up data analysis. The investigated standard products are those
produced by the MERIS (algal 1 and algal 2) and MODIS (OC3M) algorithms. The alternative data products include
those generatedwithin the CoastColour Project and Ocean Color Climate Change Initiative (OC-CCI) funded
by ESA, as well as a neural net model trained with field measurements collected in the Atlantic off Portugal
(MLPATLP). Statistical analyses showed that satellite Chl estimates tend to be larger than in situ reference values.
The study also revealed that a non-uniform Chl distribution in the water column can be a concurring factor to the
documented overestimation tendency when considering larger optical depth match-up stations. Among standard
remote sensing products, MODIS OC3M and MERIS algal 2 yield the best agreement with in situ data. The
performance of MLPATLP highlights the capability of regional solutions to further improve Chl retrieval by accounting
for environmental specificities. Results also demonstrate the relevance of oceanographic regions such
as the Nazaré area to evaluate how complex hydrodynamic conditions can influence the quality of Chl products.This studywas performed in the framework
of HabSpot FCT Project, PTDC/MAR/100348/2008 and European
Space Agency projects DUE CoastColour (ESRIN/AO/1-6141/09/l-EC)
and Climate Change Iniciative â Ocean Color (AO-1/6207/09/I-LG).
The work has been also partially supported by the European Space
Agency within the framework of the MERIS Validation Activities under
contract n. 12595/09/I-OL, and sampling activities benefited from
European projects HERMES (GOCE-CT-2005-511234) and Hermione
(EC contract 226354) support. We would like to thank NASA OBPG for
the MODIS data and ESA Project AOPT-2423 for providing MERIS full
resolution images. Ana C. Brito was funded
by a Portuguese Post-doc grant from FCT (BPD/63017/2009) and by the
Investigador FCT Program (IF/00331/2013). Davide D'Alimonte was
funded by Investigador FCT Program (IF/00541/2013).info:eu-repo/semantics/publishedVersio
Estimativas de herdabilidade e tendĂȘncias genĂ©ticas para caracterĂsticas de crescimento e reprodutivas em bovinos da raça Nelore: Estimates of heritability and genetic trends for growth and reproduction traits in Nelore cattle
Salmonella enterica: isolamento e soroprevalĂȘncia em suĂnos abatidos no Rio Grande do Sul
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