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At least 19 recordsLinked to original sources
PubMed1996

The flexible migratory orientation system of the savannah sparrow (Passerculus sandwichensis)

The orientation system of the Savannah sparrow (Passerculus sandwichensis) is typical of nocturnal migrant passerine birds. It is based on a system of interacting compass senses: magnetic, star, polarized light and, perhaps, sun compasses. The magnetic compass capability develops in birds that have never seen the sky, but the preferred direction of magnetic orientation may be calibrated by celestial rotation (stars at night and polarized skylight patterns during the day). This ability to recalibrate magnetic orientation persists throughout life and enables the bird to compensate for variability in magnetic declination that may be encountered as it migrates. The polarized light compass may be manipulated by exposing young birds to altered patterns of skylight polarization. There is some evidence that the magnetic field may be involved in calibration of the polarized light compass. In short-term orientation decision-making during migration, visual information at sunset overrides both stars and magnetic cues, and polarized skylight is the relevant stimulus in dusk orientation. The star pattern compass seems to be of little importance. This extremely flexible orientation system enables the birds to respond to spatial and temporal variability in the quality and availability of orientation information.

Journal Article↗
PubMed1993

[The therapeutics of Paracelsus with reference to natural philosophy, alchemy and psychology].

The controversial reception of Paracelsus is still going on. The crucial question is whether he is a man of the Middle Ages or of modern times. It is not possible to give a simple answer. We have to study the writings of Paracelsus within the scientific and cultural context of the Renaissance. This period is characterized by a new concept of natural philosophy. The theory of signature tries to read or translate certain constellations within the natural environment as a secret code. The idea of a sympathetic correspondence between natural bodies or substances implies the possibility of magical healing. A wellknown example is the preparation of the 'weapon salve'. There are two realities of spiritual powers at the same time: demons from the outside of the human body and powers of the mind from its inside which influence the body functions. The natural philosophy of the Renaissance tries to 'naturalize' the demons as a complement of matter. Paracelsus reflects the ideas of his time. The human being has got two bodies: a visible one which belongs to earth and an invisible one which belongs to heaven. The 'philosopher' as a pharmacist and a doctor has to detect the invisible body corresponding with the celestial world (stars, planets) by analysing the manifest astrological signs. The alchemical preparation of remedies has to purify the specific healing substances ('arcana') from the crude material. The pharmacist and doctor just imitates artificially the quasi alchemical metabolic process of nature itself continuing and finishing it. Paracelsus' concept of imagination ('imaginatio') implies a psychosomatic model how far spiritual powers can influence the body functions. Paracelsus stresses radically the importance of suggestions as a source of illness. The synchronical concepts are confusing today. Knowledge and superstition, scientific rationality and irrational speculations come together and can hardly be separated. Nevertheless, at the end of the 20th century we may have more mental relations to this scenario than we are able to realize it at the moment.

Alchemy↗
PubMed2005

[A wavelet-transform-based method for the automatic detection of late-type stars].

The LAMOST project, the world largest sky survey project, urgently needs an automatic late-type stars detection system. However, to our knowledge, no effective methods for automatic late-type stars detection have been reported in the literature up to now. The present study work is intended to explore possible ways to deal with this issue. Here, by "late-type stars" we mean those stars with strong molecule absorption bands, including oxygen-rich M, L and T type stars and carbon-rich C stars. Based on experimental results, the authors find that after a wavelet transform with 5 scales on the late-type stars spectra, their frequency spectrum of the transformed coefficient on the 5th scale consistently manifests a unimodal distribution, and the energy of frequency spectrum is largely concentrated on a small neighborhood centered around the unique peak. However, for the spectra of other celestial bodies, the corresponding frequency spectrum is of multimodal and the energy of frequency spectrum is dispersible. Based on such a finding, the authors presented a wavelet-transform-based automatic late-type stars detection method. The proposed method is shown by extensive experiments to be practical and of good robustness.

Algorithms↗
PubMed1997

Planetary nebulae: understanding the physical and chemical evolution of dying stars.

Planetary nebulae are one of the few classes of celestial objects that are active in every part of the electromagnetic spectrum. These fluorescing and often dusty expanding gaseous envelopes were recently found to be quite complex in their dynamics and morphology, but refined theoretical models can account for these discoveries. Great progress was also made in understanding the mechanisms that shape the nebulae and the spectra of their central stars. In addition, applications for planetary nebulae have been worked out; for example, they have been used as standard candles for long-range distances and as tracers of the enigmatic dark matter.

Astronomical Phenomena↗
PubMed2000

Brown dwarfs: at last filling the gap between stars and planets.

Until the mid-1990s a person could not point to any celestial object and say with assurance that "here is a brown dwarf." Now dozens are known, and the study of brown dwarfs has come of age, touching upon major issues in astrophysics, including the nature of dark matter, the properties of substellar objects, and the origin of binary stars and planetary systems.

Journal Article↗
PubMed2004

Observational properties of pulsars.

Pulsars are remarkable clocklike celestial sources that are believed to be rotating neutron stars formed in supernova explosions. They are valuable tools for investigations into topics such as neutron star interiors, globular cluster dynamics, the structure of the interstellar medium, and gravitational physics. Searches at radio and x-ray wavelengths over the past 5 years have resulted in a large increase in the number of known pulsars and the discovery of new populations of pulsars, posing challenges to theories of binary and stellar evolution. Recent images at radio, optical, and x-ray wavelengths have revealed structures resulting from the interaction of pulsar winds with the surrounding interstellar medium, giving new insights into the physics of pulsars.

Journal Article↗
PubMed2001

Reed warbler orientation: initiation of nocturnal migratory flights in relation to visibility of celestial cues at dusk.

We used radiotelemetry to investigate the time of migratory flight initiation relative to available celestial orientation cues and departure direction of a nocturnal passerine migrant, the reed warbler, Acrocephalus scirpaceus, during autumn migration. The study was carried out at Falsterbo, a coastal site in southwest Sweden. The warblers initiated migration from times well after local sunset and well into the night, corresponding to sun elevations between -4 degrees and -35 degrees, coinciding with the occurrence of stars at night. They departed in the expected migratory direction towards south of southwest with a few initiating migration in reverse directions towards northeast to east. Flight directions under overcast conditions (7-8/8) were more scattered than under clear sky conditions (0-4/8). There were fewer clouds on departure nights than on nights when the birds did not initiate migration. For birds staying longer than one night at stopover the horizontal visibility was higher and precipitation was less likely on departure nights than on the previous night. The results show that the visibility of celestial cues, and stars in particular, are important for the decision to initiate migration in reed warblers. However, cloud cover, horizontal visibility and precipitation might be correlated with other weather variables (i.e. wind or air pressure) that are also likely to be important for the decision to migrate. Copyright 2001 The Association for the Study of Animal Behaviour.

Journal Article↗