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Background: There is little information on the effect of interaction between grazing intensity and nitrogen fertilization on the productive characteristics of ryegrass (Lolium multiflorum Lam). The objective of this work was to evaluate the effect of grazing intensity and nitrogen fertilization on the productive characteristics of ryegrass pasture in a crop-livestock integration system. Methods: A randomized complete block experimental design with a 2×2×5 factorial arrangement was used, with three replications. The study factors were two management grass heights, low height (LH=10 cm) and high height (HH = 25 cm), two different nitrogen fertilization times (NP = nitrogen applied to pasture and NG = nitrogen applied to grains crop) and five evaluation periods. Result: The forage mass was higher at higher handling heights and with lower stocking rate (HH = 3995 kg DM ha-1). The forage density tended to be higher in the plots with lower grass height and nitrogen fertilization (LH = 193.5 and NP = 184.7 kg DM ha-1 cm-1). The highest accumulation rate (AR) and forage production (FP) was observed in managed pastures with HHNP (AR = 120.4 kg DM ha-1 day-1; FP = 18471 kg DM ha-1). The management of grass with HHNP provided higher forage mass, higher accumulation rate and higher dry matter production in ryegrass pasture, due to an adequate stocking rate. [ABSTRACT FROM AUTHOR]

We report on a seismic isolator with a relatively compact 3 m stack, combining new passive isolation techniques. It consists of three cascaded passive 3D isolator stages suspended from an Ultra Low Frequency (ULF) horizontal Robert linkage stage which itself is suspended from a ULF 3D pre-isolator. The 3D isolators use self-damping pendulums and Euler springs for the horizontal and vertical stages respectively, while the 3D pre-isolator is the combination of an inverse pendulum which provides low frequency horizontal pre-isolation, and a LaCoste linkage for low frequency vertical pre-isolation. Two isolators suspending mirror test masses have been built to form a 72 m optical cavity in order to test their performance. We report results which demonstrate residual motion at nanometer level at frequencies above 1 Hz. [ABSTRACT FROM AUTHOR]

High performance vibration isolators are required for ground based gravitational wave detectors. To attain very high performance at low frequencies we have developed multistage isolators for the proposed Australian International Gravitational Observatory detector in Australia. New concepts in vibration isolation including self-damping, Euler springs, LaCoste springs, Roberts linkages, and double preisolation require novel sensors and actuators. Double preisolation enables internal feedback to be used to suppress low frequency seismic noise. Multidegree of freedom control systems are required to attain high performance. Here we describe the control components and control systems used to control all degrees of freedom. Feedback forces are injected at the preisolation stages and at the penultimate suspension stage. There is no direct actuation on test masses. A digital local control system hosted on a digital signal processor maintains alignment and position, corrects drifts, and damps the low frequency linear and torsional modes without exciting the very high Q-factor test mass suspension. The control system maintains an optical cavity locked to a laser with a high duty cycle even in the absence of an autoalignment system. An accompanying paper presents the mechanics of the system, and the optical cavity used to determine isolation performance. A feedback method is presented, which is expected to improve the residual motion at 1 Hz by more than one order of magnitude. [ABSTRACT FROM AUTHOR]

Abstract: Interferometric gravitational wave detectors use triangular ring cavities to filter spatial and frequency instabilities from the input laser beam. The next generation of interferometric detectors will use high laser power and greatly increased circulating power inside the cavities. The increased power inside the cavities increases thermal effects in their mirrors. The triangular configuration of conventional mode-cleaners creates an intrinsic astigmatism that can be corrected by using the thermal effects to advantage. In this Letter we show that an astigmatism free output beam can be created if the design parameters are correctly chosen. [Copyright &y& Elsevier]

Marginally stable power recycling cavities are being used by nearly all interferometric gravitational wave detectors.With stability factors very close to unity the frequency separation of the higher order optical modes is smaller than the cavity bandwidth. As a consequence these higher order modes will resonate inside the cavity distorting the spatial mode of the interferometer control sidebands. Without losing generality we study and compare two designs of stable power recycling cavities for the proposed 5 kilometer long Australian International Gravitational Observatory (AIGO), a high power advanced interferometric gravitational wave detector. The length of various optical cavities that form the interferometer and the modulation frequencies that generate the control sidebands are also selected.