Spectral analysis of a large sample of BeppoSAX Seyfert spectra with Comptonization models: Preliminary results

We present preliminary results of the spectral analysis of a large sample of Seyfert galaxies observed by BeppoSAX. The only selection criterium was a sufficiently large S/N ratio (>10) in the PDS band (12-200 keV) to allow good detection up to the highest energy. The resulting sample is composed of 28 objects (17 Seyfert 1, 11 Seyfert 2) and 50 observations. Our main effort here is to adopt Comptonization models to fit the different spectra on a truly broad band basis (0.1-200 keV). We use two distinct disc-corona configurations, an anisotropic slab and an isotropic spherical one. We discuss the distributions of the physical parameters, like temperature and optical depth of the corona and the reflection component, among this sample. We also discussed the existence (or inexistence) of correlations between these parameters.Comment: 4 pages, 2 figures. Proc. of the meeting: "The Restless High-Energy Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers Ed

Wealth Accumulation and Growth in a Specific-Factors Model of Trade and Finance.

This paper investigates the allocative properties of an OLG specificfactors small open economy facing perfect capital mobility. Wealth formation, economic development and different labor market regimes are at the center-stage of the analysis. In a model with competitive wages and no unemployment, we find that exogenous shocks that do not affect human wealth —like the terms of trade and land endowment shifts— or the propensity to save, leave nonhuman wealth, consumption and aggregate labor unchanged; in such cases, capital formation is driven by the static effects exerted on sectoral labor. Disturbances that alter human wealth —like the world interest rate, and capital and labor taxation shocks— or the thrift rate, instead, affect nonhuman wealth and consumption as they involve an intergenerational redistribution of resources that modifies aggregate saving; labor hours supplied may be changed. In these circumstances, capital accumulation is the result of the consequences exerted on financial wealth and input demands. The consideration of a labor market with structural unemployment does not qualitatively affect the results, except for the world interest rate and the rate of time discount shifts. Our results differ substantially from those obtained in static and dynamic specific-factors setups with financial autharky.Specific-Factors; Capital Accumulation; Land; Net Foreign Assets; Finite Horizons.

Devaluation (levels versus rates) and balance of payments in a cash-in-advance economy

This paper investigates the consequences of the currency devalution, both in levels and rates, on the balance of payments in a cash-in-advance economy with finite horizons, endogenous capital accumulation and international capital immobility. In this context, a once and for all currency devaluation induces a balance of payments surplus, whereas a sustained increase in the rate of devaluation produces, in principle, an ambiguous effect on the balance of payments. If however non-restrictive assumptions on some structural parameters are made, an increase in the devaluation rate leads to a balance of payments surplus, the exact opposite of Calvo's result (1981).Devaluation; Balance of payments; Cash-in-advance constraint; Overlapping generations.

Taxing Land Rent in an Open Economy

This paper analyzes the effects of a land rent tax on capital formation and foreign investment in a life-cycle small open economy with endogenous labor-leisure choices. Differently from the previous literature, the consequences of land taxation critically depend on how the tax proceeds are used by the government. A land tax depresses capital formation, crowds out foreign investment and pulls up national wealth and consumption when consumers are lump-sum compensated for the tax. If the proceeds from taxation were used for financing un-productive government expenditure, land taxation would be neutral in its effects on capital stock, nonhuman wealth and labor. When the tax proceeds are used to reduce labor taxes, the land tax exerts ambiguous effects on capital stock and manhours, and spurs nonhuman wealth accumulation.Land Taxation, Labor Supply, Capital Accumulation, Overlapping-generations

Asset Accumulation, Fertility Choice and Nondegenerate Dynamics in a Small Open Economy

This paper shows that the assumption of elastic fertility choices represents an unconsidered way of introducing nondegenerate dynamics within an immortal small open economy, facing perfect capital mobility and no adjustment costs associated with capital accumulation, and having a fixed discount rate. The transient dynamics are obtained since fertility, which enters the Euler equation, renders the growth of the marginal utility of wealth strictly interconnected with wealth accumulation. The comparative dynamics are studied for two exogenous shocks: an increase in thrift, which changes fertility and capital formation permanently, and an increase in government spending, which alters fertility and capital stock temporarily.Endogenous population, Capital accumulation, Current account, Transitional dynamics

Optimal Taxation of Capital Income in Models with Endogenous Fertility

This paper studies the issue of the efficient taxation of capital income in intertemporal optimizing models with infinite horizons and endogenous population growth. We discover that, in the steady state, the optimal capital income tax is negative when the economy is closed. Instead, in a small open economy facing perfect capital mobility, the Chamley-Judd result of a zero tax rate is obtained if capital taxation is source-based; otherwise, income from wealth should be subsidized if taxation is residence-based. Moreover, we find that in our setup, taxing capital income with immediate expensing of capital expenditure may replicate the first-best equilibrium when labor is subsidized. Our findings, which depart substantially from those obtained in representative agent models with an endogenous labor supply, are to be ascribed to a wealth effect in the fertility choices that directly affects the pseudo-welfare function of the social planner.Factor Income Taxes; Second-best Analysis; Endogenous Population Growth; Capital Formation

Reflection at large distance from the central engine in Seyferts

We consider the possibility that most of the reflection component, observed in the hard X-ray spectra of Seyfert galaxies, could be formed on an extended medium, at large distance from the central source of primary radiation (e.g. on a torus). Then, the reflector cannot respond to the rapid fluctuations of the primary source. The observed reflected flux is controlled by the time-averaged primary spectrum rather than the instantaneous (observed) one. We show that this effect strongly influence the spectral fits parameters derived under the assumption of a reflection component consistent with the primary radiation. We find that a pivoting primary power-law spectrum with a nearly constant Comptonised luminosity may account for the reported correlation between the reflection amplitude $R$ and the spectral index $\Gamma$.Comment: Proceeding of the meeting "X-ray emission from accretion onto black hole" 20-23 June 2001, Hopkins University, Baltimore, USA (style file jhuwkshp.sty included

Genetic issues in the diagnosis of dystonias

Dystonias are heterogeneous hyperkinetic movement disorders characterized by involuntary muscle contractions which result in twisting and repetitive movements and abnormal postures. Several causative genes have been identified, but their genetic bases still remain elusive. Primary Torsion Dystonias (PTDs), in which dystonia is the only clinical sign, can be inherited in a monogenic fashion, and many genes and loci have been identified for autosomal dominant (DYT1/TOR1A; DYT6/THAP1; DYT4/TUBB4a; DYT7; DYT13; DYT21; DYT23/CIZ1; DYT24/ANO3; DYT25/GNAL) and recessive (DYT2; DYT17) forms. However most sporadic cases, especially those with late-onset, are likely multifactorial, with genetic and environmental factors interplaying to reach a threshold of disease. At present, genetic counseling of dystonia patients remains a difficult task. Recently non-motor clinical findings in dystonias, new highlights in the pathophysiology of the disease, and the availability of high-throughput genome-wide techniques are proving useful tools to better understand the complexity of PTD genetics. We briefly review the genetic basis of the most common forms of hereditary PTDs, and discuss relevant issues related to molecular diagnosis and genetic counseling