Fluid thrust control system

A pure fluid thrust control system is described for a pump-fed, regeneratively cooled liquid propellant rocket engine. A proportional fluid amplifier and a bistable fluid amplifier control overshoot in the starting of the engine and take it to a predetermined thrust. An ejector type pump is provided in the line between the liquid hydrogen rocket nozzle heat exchanger and the turbine driving the fuel pump to aid in bringing the fluid at this point back into the regular system when it is not bypassed. The thrust control system is intended to function in environments too severe for mechanical controls

Diffractive charged meson pair production

We investigate the possibility to measure the nonforward gluon distribution function by means of diffractively produced \pi^+\pi^- and K^+K^- pairs in polarized lepton nucleon scattering. The resulting cross sections are small and are dominated by the gluonic contribution. We find relatively large spin asymmetries, both for \pi^+\pi^- and for K^+K^- pairs.Comment: 15 pages, version with changed kinematical cuts, to be pubished in Phys.Lett.

The first-mover advantage in scientific publication

Mathematical models of the scientific citation process predict a strong "first-mover" effect under which the first papers in a field will, essentially regardless of content, receive citations at a rate enormously higher than papers published later. Moreover papers are expected to retain this advantage in perpetuity -- they should receive more citations indefinitely, no matter how many other papers are published after them. We test this conjecture against data from a selection of fields and in several cases find a first-mover effect of a magnitude similar to that predicted by the theory. Were we wearing our cynical hat today, we might say that the scientist who wants to become famous is better off -- by a wide margin -- writing a modest paper in next year's hottest field than an outstanding paper in this year's. On the other hand, there are some papers, albeit only a small fraction, that buck the trend and attract significantly more citations than theory predicts despite having relatively late publication dates. We suggest that papers of this kind, though they often receive comparatively few citations overall, are probably worthy of our attention.Comment: 7 pages, 3 figure

Resolution of Nested Neuronal Representations Can Be Exponential in the Number of Neurons

Collective computation is typically polynomial in the number of computational elements, such as transistors or neurons, whether one considers the storage capacity of a memory device or the number of floating-point operations per second of a CPU. However, we show here that the capacity of a computational network to resolve real-valued signals of arbitrary dimensions can be exponential in N, even if the individual elements are noisy and unreliable. Nested, modular codes that achieve such high resolutions mirror the properties of grid cells in vertebrates, which underlie spatial navigation

The benefits of family ownership, control and management on financial performance of firms

The benefits of family ownership and control of firms are at the center of the family firm debate. Previous studies have used either family ownership or management as proxies for control. Both indicators are off the mark, as they do not measure decision control as intended by the theory of the firm. This is the first study investigating the direct influence of family ownership, control and management on financial firm performance, while controlling for goal heterogeneity of different stakeholders. Our results clearly show that family control is beneficial for all stakeholders, while neither family ownership nor management influences financial performance. Monitoring behavior of families is the central component and essence of family firms and can be used as a point of departure for the development of a unified theory of family firms

Corporate governance in newly listed companies

Topics in corporate governance have been around in the literature almost for a century, most of the theoretical and empirical work has focused on the large and public company. While this research has improved our understanding of how large corporations are governed, corporate governance in small and medium sized enterprises and in particular in entrepreneurial and newly listed firms has rarely been studied. This essay offers a reflective overview of corporate governance mechanisms in entrepreneurial and newly listed companies and of why and how governance mechanisms differ from those in large and publicly traded corporations. In contrast to the traditional approach in corporate governance, we do not rely on the agency perspective as a work-horse to analyze governance problems. Instead we focus on either market or institutional based mechanisms in corporate governance. This opens the view on governance problems in newly listed companies outside the narrow view of either an agency or free-market perspective. Instead, the following study tries to bridge the different perspectives on corporate governance. From the broad set of mechanisms in corporate governance discussed in the literature, we focus only on a small subset which is prevalent in newly listed companies like the product and capital market, the market for corporate control, boards of directors and capital structures

Detailed studies of non-linear magneto-optical resonances at D1 excitation of Rb-85 and Rb-87 for partially resolved hyperfine F-levels

Experimental signals of non-linear magneto-optical resonances at D1 excitation of natural rubidium in a vapor cell have been obtained and described with experimental accuracy by a detailed theoretical model based on the optical Bloch equations. The D1 transition of rubidium is a challenging system to analyze theoretically because it contains transitions that are only partially resolved under Doppler broadening. The theoretical model took into account all nearby transitions, the coherence properties of the exciting laser radiation, and the mixing of magnetic sublevels in an external magnetic field and also included averaging over the Doppler profile. Great care was taken to obtain accurate experimental signals and avoid systematic errors. The experimental signals were reproduced very well at each hyperfine transition and over a wide range of laser power densities, beam diameters, and laser detunings from the exact transition frequency. The bright resonance expected at the F_g=1 --> F_e=2 transition of Rb-87 has been observed. A bright resonance was observed at the F_g=2 --> F_e=3 transition of Rb-85, but displaced from the exact position of the transition due to the influence of the nearby F_g=2 --> F_e=2 transition, which is a dark resonance whose contrast is almost two orders of magnitude larger than the contrast of the bright resonance at the F_g=2 --> F_e=3 transition. Even in this very delicate situation, the theoretical model described in detail the experimental signals at different laser detunings.Comment: 11 pages, 9 figure

Near-Infrared Spectroscopy of McNeil's Nebula Object

We present 0.8-5.2 micron spectroscopy of the compact source at the base of a variable nebula (McNeil's Nebula Object) in the Lynds 1630 dark cloud that went into outburst in late 2003. The spectrum of this object reveals an extremely red continuum, CO bands at 2.3-2.5 microns in emission, a deep 3.0 micron ice absorption feature, and a solid state CO absorption feature at 4.7 microns. In addition, emission lines of H, Ca II, Mg I, and Na I are present. The Paschen lines exhibit P Cygni profiles, as do two lines of He I, although the emission features are very weak in the latter. The Brackett lines, however, are seen to be purely in emission. The P Cygni profiles clearly indicate that mass outflow is occurring in a wind with a velocity of ~400 km/s. The H line ratios do not yield consistent estimates of the reddening, nor do they agree with the extinction estimated from the ice feature (A_V ~ 11). We propose that these lines are optically thick and are produced in a dense, ionized wind. The near-infrared spectrum does not appear similar to any known FUor or EXor object. However, all evidence suggests that McNeil's Nebula Object is a heavily-embedded low-mass Class I protostar, surrounded by a disk, whose brightening is due to a recent accretion event.Comment: 11 pages, 2 ps figures, accepted for publication in ApJ Letter

Universitäten als regionale Förderer der Wirtschaft?

In diesem Beitrag werden mögliche Einflussfaktoren auf die Standortentscheidung von Unternehmen in der Umgebung von Universitäten aufgezeigt. Dabei wird auf Studien zurückgegriffen, die anhand der am Neuen Markt gelisteten Unternehmen durchgeführt wurden. Als wesentliche Einflussfaktoren auf die Ansiedlung von Unternehmen in räumlicher Nähe zu Universitäten erweisen sich die Anzahl der Studenten sowie die Forschungsleistungen, vor allem im Bereich der Naturwissenschaften. Zudem macht sich für Unternehmen die räumliche Nähe zu einer forschungsintensiven Universität längerfristig in einer überdurchschnittlichen Entwicklung am Aktienmarkt bezahlt.Wirtschaftsförderung; Regionalpolitik; Hochschule; Forschungskooperation; Betriebliche Standortwahl; Standortfaktor

Anisotropy in the helicity modulus of a quantum 3D XY-model: application to YBCO

We present a variational study of the helicity moduli of an anisotropic quantum three-dimensional (3D) XY-model of YBCO in superconducting state. It is found that both the ab-plane and the c-axis helicity moduli, which are proportional to the inverse square of the corresponding magnetic field penetration depth, vary with temperature T as T to the fourth power in the zero temperature limit. Moreover, the c-axis helicity modulus drops with temperature much faster than the ab-plane helicity modulus because of the weaker Josephson couplings along the c-axis compared to those along the ab-plane. These findings are in disagreement with the experiments on high quality samples of YBCO.Comment: 9 pages, 1 figur