Biology can use trained animals

The use of trained animals to solve complicated biological problems related to psychology is discussed. Data cover sensory and motor capacity. Several examples and experiments are described

Active rendezvous between a low-earth orbit user spacecraft and the Space Transportation System (STS) shuttle

Active rendezvous of an unmanned spacecraft with the Space Transportation System (STS) Shuttle is considered. The various operational constraints facing both the maneuvering spacecraft and the Shuttle during such a rendezvous sequence are discussed. Specifically, the actively rendezvousing user spacecraft must arrive in the generic Shuttle control box at a specified time after Shuttle launch. In so doing it must at no point violate Shuttle separation requirements. In addition, the spacecraft must be able to initiate the transfer sequence from any point in its orbit. The four-burn rendezvous sequence incorporating two Hohmann transfers and an intermediate phasing orbit as a low-energy solution satisfying the above requirements are discussed. The general characteristics of the four-burn sequence are discussed, with emphasis placed on phase orbit altitude and delta-velocity requirements. The planning and execution of such a sequence in the operational environment are then considered. Factor crucial in maintaining the safety of both spacecraft, such as spacecraft separation and contingency analysis, are considered in detail

Outflow 20--2000 AU from a High-Mass Protostar in W51-IRS2

We present the results of the first high angular resolution observations of SiO maser emission towards the star forming region W51-IRS2 made with the Very Large Array (VLA) and Very Long Baseline Array (VLBA). Our images of the water maser emission in W51-IRS2 reveal two maser complexes bracketing the SiO maser source. One of these water maser complexes appears to trace a bow shock whose opening angle is consistent with the opening angle observed in the distribution of SiO maser emission. A comparison of our water maser image with an image constructed from data acquired 19 years earlier clearly shows the persistence and motion of this bow shock. The proper motions correspond to an outflow velocity of 80 km/s, which is consistent with the data of 19 years ago (that spanned 2 years). We have discovered a two-armed linear structure in the SiO maser emission on scales of ~25 AU, and we find a velocity gradient on the order of 0.1 km/s/AU along the arms. We propose that the SiO maser source traces the limbs of an accelerating bipolar outflow close to an obscured protostar. We estimate that the outflow makes an angle of <20 degrees with respect to the plane of the sky. Our measurement of the acceleration is consistent with a reported drift in the line-of-sight velocity of the W51 SiO maser source.Comment: 19 pages, 5 figures (including 3 color). Accepted for publication in ApJ (April 1, 2001 issue

Asymmetry in the Spectrum of High-Velocity H2O Maser Emission Features in Active Galactic Nuclei

We suggest a mechanism for the amplification of high-velocity water-vapor maser emission features from the central regions of active galactic nuclei. The model of an emitting accretion disk is considered. The high-velocity emission features originate in the right and left wings of the Keplerian disk. The hyperfine splitting of the signal levels leads to an asymmetry in the spectral profile of the water vapor maser line at a frequency of 22.235 GHz. We show that the gain profile asymmetry must lead to an enhanced brightness of the blueshifted high-velocity emission features compared to the redshifted ones. Such a situation is observed in the source UGC 3789.Comment: 11 pages 3 figure

A 4% Geometric Distance to the Galaxy NGC4258 from Orbital Motions in a Nuclear Gas Disk

The water maser in the mildly active nucleus in the nearby galaxy NGC4258 traces a thin, nearly edge-on, subparsec-scale Keplerian disk. Using the technique of very long baseline interferometry, we have detected the proper motions of these masers as they sweep in front of the central black hole at an orbital velocity of about 1100 km/s. The average maser proper motion of 31.5 microarcseconds per year is used in conjunction with the observed acceleration of the masers to derive a purely geometric distance to the galaxy of 7.2 +- 0.3 Mpc. This is the most precise extragalactic distance measured to date, and, being independent of all other distance indicators, is likely to play an important role in calibrating the extragalactic distance scale.Comment: 11 pages, 3 figures. Accepted for publication in Natur

NATURE AS NURTURE: BEHAVIORISM AND THE INSTINCT DOCTRINE

The main goal of this paper is to show how, in the study of action, contemporary American environmentalism absorbed intact the key concept of the nativism it displaced in the period between 1920-1935. The nature-nurture antagonism has been enacted many times in the history of psychology, in many guises. In the study of sensation and perception, of knowledge, of general mental capacity, of chronological development, of language, of individual differences in any of the foregoing, the historian can find the competing claims of empiricists and nativists, often in repeating cycles of intellectual fashion. This paper focuses, however, on just one of the many disputed areas-the study of action or behavior-and further limits itself geographically and chronologically to America in the period roughly between the two World Wars. This instance of the nature-nurture polarity beckons historical study, first of all, because of its relative clarity and definiteness. A second reason for study is that there are unmistakable signs of the return trip of the pendulum towards the nativist side. Contemporary findings and theories in the study of cognitive development, language, visual space perception, schizophrenia, human learning ability, and the growing popularity of ethological research epitomize the shifting bias, away from environmentalist and towards nativist accounts. In the case of the analysis of behavior, however, the return trip may be unexpectedly short, for it can be shown that there was substantially less actual movement of the pendulum when behaviorism prevailed over the instinct doctrine in the early 1920&apos;s. In the space of just a few years, the established instinct theories of behavior largely vanished, yielding to the onslaught of American behaviorism, with its ostensibly radical environmentalism. The two schools at times confronted each other literally, as when the instinct theorist, William McDougall debated, in 1924, with John B. Watson, the founder of behaviorism as a self-conscious schoo