The ACTS multibeam antenna

The Advanced Communications Technology Satellite (ACTS) to be launched in 1993 introduces several new technologies including a multibeam antenna (MBA) operating at Ka-band. The satellite is introduced briefly, and then the MBA, consisting of electrically similar 30 GHz received and 20 GHz transmit offset Cassegrain systems utilizing orthogonal linear polarizations, is described. Dual polarization is achieved by using one feed assembly for each polarization in conjunction with nested front and back subreflectors, the gridded front subreflector acting as a window for one polarization and a reflector for the other. The antennas produce spot beams with approximately 0.3 deg beamwidth and gains of approximately 50 dbi. High surface accuracy and high edge taper produce low sidelobe levels and high cross-polarization isolation. A brief description is given of several Ka-band components fabricated for ACTS. These include multiflare antenna feedhorns, beam-forming networks utilizing latching ferrite waveguide switches, a 30 GHz high mobility electron transmitter (HEMT) low-noise amplifier and a 20 GHz TWT power amplifier

Color naming reflects both perceptual structure and communicative need

Gibson et al. (2017) argued that color naming is shaped by patterns of communicative need. In support of this claim, they showed that color naming systems across languages support more precise communication about warm colors than cool colors, and that the objects we talk about tend to be warm-colored rather than cool-colored. Here, we present new analyses that alter this picture. We show that greater communicative precision for warm than for cool colors, and greater communicative need, may both be explained by perceptual structure. However, using an information-theoretic analysis, we also show that color naming across languages bears signs of communicative need beyond what would be predicted by perceptual structure alone. We conclude that color naming is shaped both by perceptual structure, as has traditionally been argued, and by patterns of communicative need, as argued by Gibson et al. - although for reasons other than those they advanced

Veränderungen im Eintrag von Schadstoffen in die Umwelt. Hochauflösende geochemische Sedimentuntersuchung in zwei Stauseen der Ruhr (Nordrhein-Westfalen)

Datierte Sedimentkerne aus zwei Ruhr-Stauseen wurden auf den zeitlichen Verlauf ihrer Belastung mit organischen Schadstoffen untersucht. Es wurden die Gehalte von n-Alkanen, Biomarkern (Terpanen), PAK, PCB, Tensidbegleitstoffen (LAB, TPB, NP, Phosphat) und Fäkalsterolen (z.B. Koprostanol) bestimmt. Sie wurden durch Bleikonzen-trationen und -isotopie ergänzt. Die durchgeführte organische Analytik beinhaltet Lösemittelextraktion, gefolgt von einer Flüssigchromatographie und einer Quantifizierung mittels GC/GC-MS. Aus der chronologischen Entwicklung der Schadstoffbelastung in den Sedimenten lassen sich Rückschlüsse auf (1) Emissionsquellen, (2) Eintragspfade und (3) den Einfluß von Umwelt-schutz-maßnahmen ziehen. Es zeigt sich, daß Kohleverbrennung den Hauptanteil an PAK-Emissionen trägt. Über PAK-Ratios läßt sich der Straßenverkehr als weiterer Emittent identifizieren. Das gleiche gilt für die gesättigten Kohlenwasserstoffe, bei denen die n-Alkane hauptsächlich aus der Kohleverbrennung, die Terpene jedoch aus dem Verkehr stammen. Die PCB-Einträge sind zum einen an deren globale Nutzung, zum anderen an die regionale industrielle Entwicklung gekoppelt. Der Konzentrationsverlauf der abwasserbürtigen Tensid-begleitstoffe reagiert auf Veränderungen im Verbrauch und in der Abwasserreinigung. Eine Verbesserung der Klärleistung wird auch von der Entwicklung der Fäkalsterol-zusammen-setzung bestätigt. Die für die einzelnen Stoffklassen ermittelten Responsefaktoren liegen im allgemeinen bei nur wenigen Jahren. Sie unterstützen die These, daß die Schadstoffe in den Sedimenten über-wiegend auf lokale Einträge zurückzuführen sind, und Umweltregulierungsmaßnahmen erfolgreich zur Emissionsreduzierung beigetragen haben

Ficino on the Exalted and Suffering Body: Comparing the Platonic Theology and On the Christian Religion

To what extent does Marsilio Ficino’s Platonic theology correspond to his Christian theology? This question, although too wide to grasp all at once, furnishes the inspiration for the following essay. Here I discuss the human body in the Platonic Theology — the human body as an intellectual helpmate, companion to the soul, and site of spiritual danger. I then consider the significance of the body in On the Christian Religion, Ficino’s major Christian theological statement. I show how the meaning of physical suffering in this latter treatise corresponds to the Platonic Theology and transcends it. I conclude the paper by arguing that physical suffering, for Ficino, embeds the Christian within the history of the Church

The March of the Muses: The Development of Higher Education in Athens from Pericles to the Paripatos

Western society has been greatly influenced in numerous ways by ancient Greek society and culture, not the least of which was the Greek educational system. Alexander the Great's conquests relied in many ways upon technology, philosophy, and mathematics taught in Greek institutions of higher learning. How ironic then, that even two centuries prior to Alexander the Great, in the fifth century BC, a clear concept of higher education had yet to be developed. The development in Greek and Hellenistic education from the fifth to the third centuries BC bordered on the miraculous: from having no higher education whatsoever, Greek society developed and built a fairly complex system. This essay will attempt to take a closer look into the development of Greek education itself, focusing on several key movements and characters

Scenes with the Earth as Actor: Agency and the Early-Modern Earth

This essay asks how several major figures of Renaissance and early-modern philosophy saw the Earth as agential. It argues that the Earth's agency served as a well-articulated and fundamental concept in their philosophies. That is, figures like Giordano Bruno and Johannes Kepler conceived of the Earth's agency such that it solved key problems in their cosmological systems. The essay is inspired by Bruno Latour's ecological thought, even as it acts as a corrective to certain of his assertions about early modernity. The essay concludes with some practical lessons that might be taken from early modernity