Optimization-based comparison of different approaches for the automatized calculation of residual stresses and fiber orientations in arteries

Residual stresses and fiber orientations in arterial walls can be approximated by means of the simulation of growth and remodeling processes. In order to enable a comparison of different approaches of combined growth and remodeling in one framework, a method based on the optimization of model parameters is developed. The minimization of a mechano-biologically motivated objective function permits to evaluate the approaches with respect to their ability of effectively reducing stress peaks and stress inhomogeneities in the arterial wall. This examination is performed for a simplified, one-layered, rotationally symmetric arterial segment in order to enable the analysis of the fundamental mechanisms included in the individual model variants. Once the most probable growth mechanism is identified, multi-layered segments can be analyzed in more detail

The Geometry of Fractional D1-branes

We find explicit solutions of Type IIB string theory on R^4/Z_2 corresponding to the classical geometry of fractional D1-branes. From the supergravity solution obtained, we capture perturbative information about the running of the coupling constant and the metric on the moduli space of N=4, D=2 Super Yang Mills.Comment: 13 pages, no figures, minor corrections, clarifications to the text in section

Analyzing Baryon Acoustic Oscillations in Sparse Spectroscopic Samples via Cross-Correlation with Dense Photometry

We develop a formalism for measuring the cosmological distance scale from baryon acoustic oscillations (BAO) using the cross-correlation of a sparse redshift survey with a denser photometric sample. This reduces the shot noise that would otherwise affect the auto-correlation of the sparse spectroscopic map. As a proof of principle, we make the first on-sky application of this method to a sparse sample defined as the z>0.6 tail of the Sloan Digital Sky Survey's (SDSS) BOSS/CMASS sample of galaxies and a dense photometric sample from SDSS DR9. We find a 2.8sigma preference for the BAO peak in the cross-correlation at an effective z=0.64, from which we measure the angular diameter distance D_M(z=0.64) = (2418 +/- 73 Mpc) (r_s/r_{s,fid}). Accordingly, we expect that using this method to combine sparse spectroscopy with the deep, high quality imaging that is just now becoming available will enable higher precision BAO measurements than possible with the spectroscopy alone.Comment: 14 pages, 4 figures; updated reference

Enlargement: A Process rather than a Point in Time. CEPS Policy Briefs No. 51, 1 April 2004

The 1st of May 2004 is being marked by numerous important political events, speeches and festivities. This is appropriate in the sense that on that day ten new member states join the EU. However, “all” that happens on May 1st is that the EU’s acquis communautaire becomes the law in the new member states. In order to make this happen, a decade of intense preparations on both sides was necessary and it will certainly take another decade before the full consequences of this enlargement will be felt. Enlargement should thus be viewed as a process, and not a single event taking place on one day. For a think tank with the motto ‘Thinking ahead for Europe’, enlargement is old news. CEPS researchers have been analysing the many issues surrounding enlargement for at least the last dozen years, when it seemed only a distant dream. Over time the debate has shifted from the basic question of whether countries that had been forced to live under communism for so long would actually be able to qualify for EU membership to the basic policy issues: What will it cost? How will it affect our security? These are the basic issues surrounding any large political project. The following pages provide a brief overview of the main findings of CEPS research on enlargement over the years. We start with an evaluation of the importance of enlargement in quantitative terms (GDP, population, etc.) and then turn to an evaluation of its broad economic impact, which is likely to be small for the old members, but large for the new members. This leads us to issue of the cost of enlargement (for the old EU-15), which is also rather small. The answer to the question ‘what is in it for us’, which is often posed in the old member countries, is thus perhaps disappointing: very little either way, in purely economic terms, there are small costs and small benefits, with probably as small net effect. Here the time dimension becomes important as the benefits will increase over time, faster than the potential costs through the EU budget. We then turn to another issue that has received a lot of attention lately concerning the free movement of labour, drawing attention to the fact that large-scale migration is unlikely at any rate. Finally, we assess the widespread concern that an enlarged EU (of 25 or 27 members) will cause gridlock in the policy-making processes of the EU institutions

Windage measurements in a rotor stator cavity with rotor mounted protrusions and bolts

This paper reports an experimental investigation of the windage associated with enclosed rotor-stator systems with superposed throughflow, as commonly found in gas turbine engines. The term windage is often used to describe the viscous heating that arises from the interaction of surfaces and fluids in rotating disc systems. Since the presence of circumferentially discreet geometric features strongly alters the magnitude of Windage measured, the physical mechanisms collectively referred to as windage in this paper are separately described as part of the discussion of results. Tests have been carried out to measure windage directly in the form of shaft torque and also rotor surface temperature. Non-dimensional flow parameters are used to expand the relevance of the data obtained, which encompasses the ranges 0.17 x 107 ≤ Reφ ≤ 1.68 x 107and 0.24 x 105 ≤ Cw ≤ 1.06 x 105 which corresponds to 0.058 ≤ λT ≤ 0.631. Data has been obtained for smooth disc geometry and also with rotor mounted protrusions of N = 3, 9 and 18; D = 10 mm, 13 mm and 16 mm diameter; H = 11 mm, high, hexagonal bolt shaped protrusions. Bi-hexagonal (twelve sided) bolts of D = 13 mm effective diameter, and height, H = 11mm, were also tested with conditions closely matched to the 13 mm hexagonal bolts. Finally, tests with 10 mm diameter, 6 mm deep, pockets were also carried out. Over the range of conditions and geometries tested, increasing the number of bolts increases the moment coefficient and windage heating. At low values of turbulent flow parameter, λT, which correspond to rotational speeds between 8000 and 10000 rev/min, increasing the diameter of the bolts shows a clear trend for both increased windage torque and average disc temperature rise. For these conditions, there also appears to be a clear reduction in windage and temperature rise with the bi-hexagonal shaped bolts compared to the equivalent diameter hexagonal bolt form. Variation in the moment coefficient with the number and diameter of bolts is attributed to variations in form drag between the different configurations. The introduction of the recesses onto the disc has very little effect on either windage heating or moment coefficient; this is attributed to the component of windage mechanism in operation and also the relatively small size in comparison to the protrusions studied here. This work contributes to the understanding of windage in gas turbines by introducing new low uncertainty data obtained at engine representative conditions and as such is of benefit to those involved with the design of internal air systems and disc fixture

Security Transaction Taxes and Market Quality

We examine nine changes in the New York State Security Transaction Taxes (STT) between 1932 and 1981. We find that imposing or increasing an STT results in wider bidask spreads, lower volume, and increased price impact of trades. In contrast to theories of STT imposition as a means to reduce volatility, we find no consistent relationship between the level of an STT and volatility. We examine the propensity of traders to switch trading locations to avoid the tax and find no consistent evidence that they will change locations. We do find evidence to suggest that taxes imposed on the par value of stock will result in corporations managing the par value in the direction of minimizing the impact of the tax on investors.Econometric and statistical methods; Financial markets; Market structure and pricing

Hot molecular hydrogen in the central parsec of the Galaxy through near-infrared 3D fitting

Aims. We have investigated neutral gas in the central cavity of the circumnuclear disk (CND) at the Galactic Center, where the ionized minispiral lies, to describe the H2 distribution and properties in this ionized environment. Methods. This study was carried out through a spectro-imaging data cube of the central cavity obtained with SPIFFI on the VLT. The observed field of view is 36"x 29" , with a spectral resolution R = 1 300 in the near-infrared. These observations cover several H2 lines. To preserve the spatial resolution and avoid edge effects, we applied a new line-fitting method that consists of a regularized 3D fitting. We also applied a more classical 1D fitting to compare the relative strength of the H2 lines. Results. We present high spatial and spectral resolution maps of the intensity, velocity, and width of five H2 lines and an extinction map derived from H2. Molecular gas is detected everywhere in the field. In particular, in addition to the known CND features, we detected an emission from the northern arm cloud and from the minicavity. The excitation diagrams allow us to estimate the temperature, mass, and density of these features. Conclusions. We interpret the CND emission as coming from a hot, thermalized, thin layer at the surface of the clouds. The observed H2 corresponds only to a small fraction of the total H2 mass. The emission remains fairly strong in the whole central cavity, but it is not thermalized. A strong deviation from thermal equilibrium is detected near the minicavity. We suggest that this emission is caused by constantly forming H2 that is destroyed again before it reaches ortho/para equilibrium