Search results for "Systematics"

On the astrobiological relevance of viruses in extraterrestrial ecosystems

2009

AbstractViruses are the dominant form of genetically reproducing entities on Earth. Yet, viruses are mostly neglected in the context of astrobiology due to their non-living nature. In this discussion it is considered whether viruses are likely to be transferred within bacterial endospores to other planetary bodies through lithopanspermia. Interestingly, it seems possible that ecosystems of panspermial origin might yield biospheres in which viruses are absent. The evolutionary pathway of life in these systems might differ significantly from the path observed on Earth. We hypothesize that the difference in the two potential ways for the emergence of life, those being panspermial or local orig…

Role of clays in protecting adsorbed DNA against X-ray radiation

2004

The X-ray emission of the young Sun was much harder and intense than today and might have played a significant role in the evolution of complex organics in protoplanetary environments. We investigate the effects of soft X-rays on tryptophan molecules in aqueous solutions at room temperature. As results of the irradiation experiments we detect several light species indicative of fragmentation, together with large molecular structures such as tryptophan dipeptide and tripeptide. Complexification is more evident in H2O solution than in D2O, probably due to isotopic effects. The abundances of peptides depend on the irradiation dose and decrease with increasing energy deposition. Radicals such a…

Wavelength dependence of visual acuity in goldfish.

2003

Visual acuity was measured in a two-choice training experiment with food reward. Four goldfish were trained to select a homogeneously illuminated testfield when a high-contrast grating (transparency) was shown for comparison at the second testfield. Measurements were performed for white and monochromatic testfield illuminations in the light adapted state. Fourteen wavelengths between 404 nm and 683 nm were tested. For each wavelength (and white light) the testfield intensity was determined for which spatial resolution was highest. Between 446 nm and 683 nm maximal values of 2.0 cycles/deg (corresponding to a visual acuity of 15' of arc) were found. At 404 nm and in the ultraviolet resolutio…

Neue Ergebnisse zur Polarisation langsamer Elektronen (0,5 bis 1,5 keV) durch elastische Streuung an freien Hg-Atomen

1964

Zur Sonnent�tigkeit vor 1750

1960

Auf der Suche nach ?seltsamer? Materie

1991

Antiproton-Proton-Wechselwirkung bei niedrigen Energien

1987

Cricket combined mechanoreceptors and kicking response

1977

1. Only those filiform hairs on the cerci ofGryllus, which are coupled with campaniform sensilla, show a) a thickening of the hair shaft at the height of the upper ring lamella of their sockets and b) a thin cuticular membrane, which surrounds their sockets. While thefiliform hairs themselves are deflected either parallel to the long axis of the cerci or perpendicular to it, thesockets of the filiform hairs may be deflected preferentially in the proximal and distal direction. 2. Spike potentials can be recorded from the sensory cells of the filiform hairs as long as these are deflected in a weak air current, but not during permanent deflection in strong air streams when they touch the inner…

Two-proton emission in the decay of Ar-31

1998

18 pages, 7 figures, 2 tables.-- PACS nrs.: 23.40.Hc; 27.30.+t.

New features in systematics of low-spin states in even106?120Cd

1990

Low- spin states in even106–112Cd and116Cd were investigated by in-beam and off-beam γ-ray and conversion electron spectroscopy. New spin assignments and decay branching ratios for the levels in106Cd,108Cd and110Cd were obtained. From the new systematical data for the even106–120Cd, it is inferred that two sets of low-lying 0+ states cross between114Cd and116Cd. One of these sets appears to have features of both intruder and two-quadrupole-phonon states.