Low-thrust solar electric propulsion navigation simulation program

An interplanetary low-thrust, solar electric propulsion mission simulation program suitable for navigation studies is presented. The mathematical models for trajectory simulation, error compensation, and tracking motion are described. The languages, input-output procedures, and subroutines are included

Optimal control of linear time delay systems

Obtaining optimal control for linear time varying system with time dela

Six-body Light-Front Tamm-Dancoff approximation and wave functions for the massive Schwinger model

The spectrum of the massive Schwinger model in the strong coupling region is obtained by using the light-front Tamm-Dancoff (LFTD) approximation up to including six-body states. We numerically confirm that the two-meson bound state has a negligibly small six-body component. Emphasis is on the usefulness of the information about states (wave functions). It is used for identifying the three-meson bound state among the states below the three-meson threshold. We also show that the two-meson bound state is well described by the wave function of the relative motion.Comment: 19 pages, RevTeX, 7 figures are available upon request; Minor errors have been corrected; Final version to appear in Phys.Rev.

Transpiration and water uptake of Senecio medley-woodii and Aloe jucunda under changing environmental conditions: measurements with a potometric water-budget-meter

Transpiration, water uptake by the roots and CO2 exchange of two leaf succulents, Senecio medleywoodii (Asteraceae) and Aloe jucunda (Asphodeliaceae), were monitored simultaneously and continuously with a gas exchange cuvette combined with an apparatus to quantify water uptake (= waterbudget- meter). Measurements, which are primarily valid for plants with a sufficient water supply, were made with the same plant for up to 29 consecutive days. Ambient air temperature varied between 17 and 35 °C with a constant dewpoint temperature of 13°C of the ambient air and a 12 h photoperiod at 400-500µmol m−2s−1 photon irradiance. The net water flux (Jw(net)=water uptake-transpiration) and the water balance (Jw(net) integrated for a timespan) were calculated. Various tests were made to determine the accuracy of the measurements made with this rather complex equipment. In most cases the errors for transpiration and uptake rates were much lower than 8% determined under the conditions of drastically (about 10 K per 30 min) increased or decreased ambient air temperatures. The experimental set-up proved to be a most valuable tool to determine and analyse interactions between transpiration and water uptake, changes in plant water status and the buffering of negative Jwnet). Increasing the temperature of ambient air resulted, for both species investigated, in a quick and considerably enhanced transpiration, but there was only a minor impact on water uptake. Water loss exceeding uptake was buffered by internal water reserves which were refilled within about 1 d after the plant was relieved of heat and drought stress caused by a period of high ambient air temperatures and high water vapour saturation deficits of the air. Repeated simulation of such stress periods showed that the absolute values of transpiration and the water uptake for 24 h can vary, but the diurnal course of the values showed the same pattern if the environmental conditions were identical. Such standardized diurnal transpiration and water uptake curves could be very useful for the validation of mathematical models used to describe plant water relation

Calculation of production and decay of radioisotopes for future irradiation experiments and ion beam facilities

Abstract.: The design of future radioactive ion beam (RIB) facilites requires the forecast of radio isotope inventory after irradiation. At CERN - ISOLDE, we developed a software that estimates the activity of irradiated materials as a function of time dedicated to radioactive waste management. This tool can also be used for licensing procedures, planning of irradiation experiments and the estimation of yield

Field Test for Repellency of Cedarwood Oil and Cedrol to Little Fire Ants

Eastern redcedars (Juniperus virginiana L.) are an abundant renew- able resource and represent a potential source of valuable natural products that may serve as natural biocides. The aromatic wood can be extracted to obtain cedarwood oil (CWO) and critical carbon dioxide (CO2) extraction of eastern redcedars gives both high yields and high quality CWO. In this study, CO2-derived CWO and cedrol, the most abundant component of CWO, were field-tested for repellency against the little fire ant (LFA), Wasmannia auropunctata Roger, in a Hawaiian macadamia orchard. Field tests were conducted using chopsticks baited with peanut-butter placed in established LFA trails on macadamia tree trunks and branches. The chopsticks and any ants present were collected after ca. 24 hours and the number of ants determined by visual counting. Four treatments were compared: Hexane only control; mineral oil; CWO; and cedrol. Control chopsticks and chopsticks treated with mineral oil had very high numbers of ants and were statistically equivalent. The CWO-treated chopsticks had significantly fewer LFAs than all the other treatments. Chopsticks treated with cedrol had fewer ants than the control chopsticks but more than the chopsticks treated with CWO. This research suggests that CWO extracts from J. virginianna may provide a renewable source of a natural ant repellent and could help manage this invasive pest

Costituent Quark Picture out of QCD in two dimensions - on the Light-Cone

Using DLCQ as a nonperturbative method, we test Fock-space truncations in ${\rm QCD}_{1+1}$ by studying the mass spectra of hadrons in colour SU(2) and SU(3) at finite harmonic resolution $K$. We include $q\bar q q\bar q$ states for mesons and up to $qqq q\bar q$ states for baryons. With this truncation, we give `predictions' for the masses of the first five states where finite $K$ effects are minimal.Comment: 13 pages, uses elsart.sty 2 Postscript figures, uses epsf.sty 'elsart.sty' and 'elsart12.sty' are available via anonymous-ftp at ftp://ftp.tex.ac.uk/tex-archive/macros/latex/contrib/supported/elsevie

International Environmental Regimes and Latin America : The Role of Environmental Non-governmental Organizations

This study analyzes the obstacles to environmental policymaking in Latin America such as the poverty crisis, the North/South conflict and political corruption. These obstacles result in weak government institutions and create an opportunity for other actors to wield greater influence in the policymaking process. This paper evaluates the effectiveness of environmental agreements such as debt-for-nature swaps. Debt-for-nature swaps emerged as a solution to the conundrum of the debt crisis and environmental degradation. The cases of Bolivia, Costa Rica and Ecuador illustrate the tensions between development and environmental degradation. The most important lesson learned from these swaps is that the support of local inhabitants is critical to the success of conservation programs. In general, debt-for-nature swaps fail to have a lasting impact on either the debt or conservation crises that they seek to alleviate. The three main perspectives of regime theory: power-based, interest-based and knowledge-based regimes provide the analytic framework for the evaluation of environmental regimes in Latin America. This study suggests that a contextual regime may be the most effective theoretical framework for environmental policymaking. The informal and nonbinding nature of contextual regimes could galvanize Latin American countries to initiate a dialogue on environmental issues and eventually result in more substantive, legal remedies over time. A key component of a contextual regime for Latin America would include a more formal and substantive role for environmental non-governmental organizations (ENGOs). A key obstacle to their participation is the traditional, state-centric model of International Relations and the central tenet of sovereignty. This paper suggests a polycentric approach, one that includes both governmental and nongovernmental actors could provide a better framework for environmental policymaking in Latin America. This study looks at how ENGOs can educate local inhabitants about sustainable farming practices, monitor environmental agreements and assist with technology transfers. Specifically, I will look at the impact of ENGOs on the 1983 and 1994 International Tropical Timber Agreements and the Global Environment Facility negotiations. The proliferation of NGOs in environmental policymaking has been likened to a quiet revolution and defining the scope and extent of their role is an issue that requires further analysis

The Vacuum in Light-Cone Field Theory

This is an overview of the problem of the vacuum in light-cone field theory, stressing its close connection to other puzzles regarding light-cone quantization. I explain the sense in which the light-cone vacuum is ``trivial,'' and describe a way of setting up a quantum field theory on null planes so that it is equivalent to the usual equal-time formulation. This construction is quite helpful in resolving the puzzling aspects of the light-cone formalism. It furthermore allows the extraction of effective Hamiltonians that incorporate vacuum physics, but that act in a Hilbert space in which the vacuum state is simple. The discussion is fairly informal, and focuses mainly on the conceptual issues. [Talk presented at {\sc Orbis Scientiae 1996}, Miami Beach, FL, January 25--28, 1996. To appear in the proceedings.]Comment: 20 pages, RevTeX, 4 Postscript figures. Minor typos correcte

Fermion Condensates and the Trivial Vacuum of Light-Cone Quantum Field Theory

We discuss the definition of condensates within light-cone quantum field theory. As the vacuum state in this formulation is trivial, we suggest to abstract vacuum properties from the particle spectrum. The latter can in principle be calculated by solving the eigenvalue problem of the light-cone Hamiltonian. We focus on fermionic condensates which are order parameters of chiral symmetry breaking. As a paradigm identity we use the Gell-Mann-Oakes-Renner relation between the quark condensate and the observable pion mass. We examine the analogues of this relation in the `t~Hooft and Schwinger model, respectively. A brief discussion of the Nambu-Jona-Lasinio model is added.Comment: 14 pages, no figures, latex2