Measurement and Simulation of Coaxial to Microstrip Transitions' Radiation Properties and Substrate Influence

A radiation and electro-magnetic (EM) field analysis of coaxial-to-microstrip transitions is presented. Radiation is quantified by simulation and measurement of a crosstalk between two Omni-Spectra's transitions using microstrip 'open' calibration standards at different positions. Simulation results are compared to the measured data and good agreement is reported on two different substrates. The evaluation method which is used to analyze quality of the transition and its radiation properties was already developed and verified on a grounded coplanar waveguide (CPWG) transmission line. Results can be used to estimate uncertainty budget of the calibrated measurement with respect to the measured radiation. Results on different substrates show interesting behaviour and can prove useful when choosing suitable substrate for specific test-fixture

International risk sharing in the short run and in the long run

Using a panel of 23 industrialised countries, the paper investigates how short-run and long-run income risks are shared and how the source of uncertainty matters for the way this risk gets insured. Surprisingly, short-term and long-term output risks are found to be equally well insured. Transitory shocks get smoothed almost completely whereas permanent shocks remain 80 percent uninsured. We find a somewhat more important role for international capital markets than earlier studies. Whereas our results tie in with some recent theoretical insights and are consistent with empirical findings on home bias in international portfolios, they raise the question why permanent shocks are so hard to insure internationally. Keywords; international consumption risk sharing, European integration, panel data, panel vector autoregressions

Intra-and International Risk-Sharing in the Short Run and the Long Run

We investigate empirically how industrialized countries and U.S. states share consumption risk at horizons between one and thirty years. U.S. federal states share about 50 percent of their permanent idiosyncratic risk through cross-state capital income flows. While insurance against transitory fluctuations in output is virtually complete, OECD countries do not share any of their permanent idiosyncratic risk. Our results suggest that purely transaction cost based theories cannot explain the home bias, since the potential welfare gains from insurance against permanent shocks would by far outweigh that of insuring against transitory variation. We conclude that permanent and transitory shocks constitute two qualitatively different kinds of risk and that various forms of endogenous market incompleteness may render permanent shocks a lot harder to insure, in particular at the international level.consumption risk sharing, home bias, international business cycles, panel vector autoregressions

Equity Fund Ownership and the Cross-Regional Diversification of Household Risk

We explore the link between portfolio home bias and consumption risk sharing among Italian regions using aggregated household level information on consumption, income and portfolio holdings. We propose to use data on equity fund ownership to proxy for regional home bias: equity funds are typically diversified at the national or international level and will therefore provide interregional diversification. In assessing the impact of equity fund ownership on interregional risk sharing we distinguish between two dimensions: variation in the share of equity funds in fund-holder's wealth (the intensive margin) and variation in the fraction of households that hold funds (the extensive margin). We find that equity fund ownership is an important determinant of interregional risk sharing. First, diversification incentives qualitatively line up with actually observed portfolio choices: fund holders in regions where households are particularly exposed to region-specific labor income risk hold a larger fraction of their wealth in (out-of-region) funds. Secondly, for a region as a whole, risk sharing increases in both the intensive and the extensive margins of diversification and the two margins reinforce each other. The marginal effect of wider equity fund participation seems particularly strong, suggesting that policies aimed at increasing equity market participation could help foster better interregional risk sharing.consumption risk sharing, regional home bias, survey of household income and wealth, labor income risk, portfolio choice, stock market participation

Upper and Lower Bounds on Long Dual-Paths in Line Arrangements

Given a line arrangement $\cal A$ with $n$ lines, we show that there exists a path of length $n^2/3 - O(n)$ in the dual graph of $\cal A$ formed by its faces. This bound is tight up to lower order terms. For the bicolored version, we describe an example of a line arrangement with $3k$ blue and $2k$ red lines with no alternating path longer than $14k$. Further, we show that any line arrangement with $n$ lines has a coloring such that it has an alternating path of length $\Omega (n^2/ \log n)$. Our results also hold for pseudoline arrangements.Comment: 19 page

Atmospheric NLTE-Models for the Spectroscopic Analysis of Blue Stars with Winds. III. X-ray emission from wind-embedded shocks

X-rays/EUV radiation emitted from wind-embedded shocks in hot, massive stars can affect the ionization balance in their outer atmospheres, and can be the mechanism responsible for the production of highly ionized species. To allow for these processes in the context of spectral analysis, we have implemented such emission into our unified, NLTE model atmosphere/spectrum synthesis code FASTWIND. The shock structure and corresponding emission is calculated as a function of user-supplied parameters. We account for a temperature and density stratification inside the post-shock cooling zones, calculated for radiative and adiabatic cooling in the inner and outer wind, respectively. The high-energy absorption of the cool wind is considered by adding important K-shell opacities, and corresponding Auger ionization rates have been included into the NLTE network. We tested and verified our implementation carefully against corresponding results from various alternative model atmosphere codes, and studied the effects from shock emission for important ions from He, C, N, O, Si, and P. Surprisingly, dielectronic recombination turned out to play an essential role for the ionization balance of OIV/OV around Teff = 45,000 K. Finally, we investigated the behavior of the mass absorption coefficient, kappa_nu(r), important in the context of X-ray line formation in massive star winds. In almost all considered cases, direct ionization is of major influence, and Auger ionization significantly affects only NVI and OVI. The approximation of a radially constant kappa_nu is justified for r > 1.2 Rstar and lambda < 18 A, and also for many models at longer wavelengths. To estimate the actual value of this quantity, however, the HeII opacities need to be calculated from detailed NLTE modeling, at least for wavelengths longer than 18 to 20 A, and information on the individual CNO abundances has to be present.Comment: accepted by A&