Astronomical observations with the University College London balloon borne telescope

The characteristics of a telescope system which was developed for high altitude balloon astronomy are discussed. A drawing of the optical system of the telescope is provided. A sample of the signals recorded during one of the flights is included. The correlation between the infrared flux and the radio continuum flux is analyzed. A far infrared map of the radio and infrared peaks of selected stars is developed. The spectrum of the planet Saturn is plotted to show intensity as compared with wavenumber

Forming efficient agent groups for completing complex tasks

In this paper we produce complexity and impossibility results and develop algorithms for a task allocation problem that needs to be solved by a group of autonomous agents working together. In particular, each task is assumed to be composed of several subtasks and involves an associated predetermined and known overall payment (set by the task’s owner) for its completion. However, the division of this payment among the corresponding contributors is not predefined. Now to accomplish a particular task, all its subtasks need to be allocated to agents with the necessary capabilities and the agents’ corresponding costs need to fall within the preset overall task payment. For this scenario, we first provide a cooperative agent system designer with a practical solution that achieves an efficient allocation. However, this solution is not applicable for non-cooperative settings. Consequently, we go on to provide a detailed analysis where we prove that certain design goals cannot be achieved if the agents are self interested. Specifically, we prove that for the general case, no protocol achieving the efficient solution can exist that is individually rational and budget balanced. We show that although efficient protocols may exist in some settings, these will inevitably be setting-specific

How BAO measurements can fail to detect quintessence

We model the nonlinear growth of cosmic structure in different dark energy models, using large volume N-body simulations. We consider a range of quintessence models which feature both rapidly and slowly varying dark energy equations of state, and compare the growth of structure to that in a universe with a cosmological constant. The adoption of a quintessence model changes the expansion history of the universe, the form of the linear theory power spectrum and can alter key observables, such as the horizon scale and the distance to last scattering. The difference in structure formation can be explained to first order by the difference in growth factor at a given epoch; this scaling also accounts for the nonlinear growth at the 15% level. We find that quintessence models which feature late $(z<2)$, rapid transitions towards $w=-1$ in the equation of state, can have identical baryonic acoustic oscillation (BAO) peak positions to those in $\Lambda$CDM, despite being very different from $\Lambda$CDM both today and at high redshifts $(z \sim 1000)$. We find that a second class of models which feature non-negligible amounts of dark energy at early times cannot be distinguished from $\Lambda$CDM using measurements of the mass function or the BAO. These results highlight the need to accurately model quintessence dark energy in N-body simulations when testing cosmological probes of dynamical dark energy.Comment: 10 pages, 7 figures, to appear in the Invisible Univers International Conference AIP proceedings serie

Using Intelligent Agents to Manage Business Processes

This paper describes work undertaken in the ADEPT (Advanced Decision Environment for Process Tasks) project towards developing an agent-based infrastructure for managing business processes. We describe how the key technology of negotiating, service providing, autonomous agents was realised and demonstrate how this was applied to the BT business process of providing a customer quote for network services

Distinct Quantum States Can Be Compatible with a Single State of Reality

Perhaps the quantum state represents information about reality, and not reality directly. Wave function collapse is then possibly no more mysterious than a Bayesian update of a probability distribution given new data. We consider models for quantum systems with measurement outcomes determined by an underlying physical state of the system but where several quantum states are consistent with a single underlying state---i.e., probability distributions for distinct quantum states overlap. Significantly, we demonstrate by example that additional assumptions are always necessary to rule out such a model.Comment: 5 pages, 2 figure

Effects of water availability on the germination of native and exotic forbs

Native and Exotic Forbes Germination Response to Drought Stress Beau R. Jennings, Mandy L. Slate, Dean E. Pearson Abstract The shifting climate of the western North American grasslands is forecasted to continue the trend of decreased annual rainfall and longer phases of rain-free windows in times where rainfall has been previously abundant. This understanding has inspired many studies on how ecosystems will respond to these changes. One of the key factors in the shaping of the ecosystem is the availability of precipitation in the spring, which will limit plant recruitment and seedling survival for the dryland ecosystem. Furthermore, seedling’s ability to establish themselves prior to hot dry summers is a key attribute to ensuring success in survival and reproduction. Yet, the expansion of exotic over native species in dryland ecosystems suggests that some exotic plants have traits that allow them to succeed at a higher success rate than native plants. Specifically, understanding the germination tendencies of exotic and native forbes will allow better predictions to be made on the future shaping of these ecosystems. We conducted an experiment in a lab comparing germination percentages and rates of germination for multiple species of native and exotic grassland forbs under different levels of water availability. The experiment was conducted in a growth chamber where temperature, lighting, and humidity were kept as constant variables. The specimens were placed in petri dishes on top of filter paper, and each petri dish lid had three ⅛” holes to allow some evaporation. We hydrated seeds with either 2ml and 3ml daily or every other day. Specimens were examined daily in order to record germination promptly. We will present a comparison of Germination synchrony, germinability, time to germination, germination t50, and germination range between native and exotic forbes species, and discuss how these findings may be used to better understand the processes in which exotic plants are able to overtake plants in their native habitats

Magsat vector magnetometer calibration using Magsat geomagnetic field measurements

From the time of its launch on Oct. 30, 1979 into a nearly polar, Sun synchronous orbit, until it reentered the Earth's atmosphere on June 11, 1980, Magsat measured and transmitted more than three complete sets of global magnetic field data. The data obtained from the mission will be used primarily to compute a currently accurate model of the Earth's main magnetic field, to update and refine world and regional magnetic charts, and to develop a global scalar and vector crustal magnetic anomaly map. The in-flight calibration procecure used for 39 vector magnetometer system parameters is described as well as results obtained from some data sets and the numerical studies designed to evaluate the results