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Biomedical subjects

T Owen

Publications and source records attributed to T Owen.

52 records · Page 3Linked to original sources
PubMed1986

Deuterium in the outer Solar System: evidence for two distinct reservoirs.

We have just completed a series of determinations of the CH3D/CH4 ratio in the atmospheres of Saturn, Titan and Uranus. These results, coupled with the work of other investigators, suggest that the Solar System contains at least two distinctly different primordial reservoirs of deuterium: that contained in gaseous hydrogen and that contained in the volatiles which have been maintained at low temperatures or isolated from hydrogen; for example, trapped in cold, solid material. Both of these reservoirs were established before the formation of the Solar System.

Atmosphere↗
PubMed1985

Life as a planetary phenomenon.

The success of recent spacecraft from the U.S.A. and the U.S.S.R. has given us a wealth of new data about the planets in our solar system. We can now develop a much better rationale for the reasons that abundant life is only found on our planet. Mars, smaller and more distant from the Sun, may nevertheless hold clues to the early development of Earth's atmosphere. The origin of life on Mars early in that planet's history cannot be ruled out. Titan offers a contemporary example of extremely primitive conditions, where chemical reactions resembling those that preceded the development of life on Earth may be occurring today. Venus and Jupiter illustrate the need for a planet to be the right size and the right distance from the sun if chemical evolution leading to the origin of life is to occur.

Atmosphere↗
PubMed1985

The Jovian stratosphere in the ultraviolet.

The center-of-disk reflectivity of Jupiter in the wavelength range from 1450 to 3150 angstroms has been computed from 30 low-dispersion IUE spectra taken during solar maximum in 1978-1980. A vertically inhomogeneous radiative transfer program is used to compute model reflectivities of various stratospheric compositions for comparison. Ammonia and acetylene are well determined because they show narrow absorption bands in the ultraviolet. Above 1800 angstroms, these two gases provide a good fit to the data, but not below. At shorter wavelengths the fit would be much improved by a small amount (0.5-1.5 ppb) of propadiene/allene (C3H4). Voyager IRIS spectra show that the IR bands of allene are not strong enough to be detected in such a small amount. Additional absorption around 1600 angstroms can be reproduced best with the presence of cyclopropane (C3H6, <15 ppb), although other absorbers (e.g., hydrocarbon molecules with more than three carbon atoms, oxygen- or nitrogen-containing molecules, or a high-altitude haze) could also explain the spectrum in this region. The data are too noisy to detect possible CO Cameron band absorption near 2000 angstroms.

Acetylene↗
PubMed1984

Uranus: microwave images.

Observations of Uranus at wavelengths of 2 and 6 centimeters with the Very Large Array were made in 1980 and 1981. The resulting maps of brightness temperature show a subsolar symmetry at 2 centimeters but a near-polar symmetry at 6 centimeters. The 6-centimeter maps show an increase in temperature from equator to pole with some evidence for a warm "ring" surrounding the north pole. The disk-average temperatures (147 +/- 5 K and 230 +/- 6 K at 2 and 6 centimeters, respectively) are distinctly lower than recently reported values; these results suggest that the secular increase in temperature reported during the last 15 years has been reversed. The variations in brightness temperature probably reflect variations in ammonia abundance in the planet's atmosphere, but the mechanism driving these variations is still unclear.

Ammonia↗
PubMed1984

Chemical evolution on the giant planets and Titan.

We summarize the current status of atmospheric chemistry in the atmospheres of the outer solar system with special emphasis on the question of HCN formation on Jupiter, differences between polar and equatorial compositions on Jupiter, the coloration of the Great Red Spot, and the unique environment of Titan.

Ammonia↗
PubMed1984

Comparing tiltmeters for crustal deformation measurement--a preliminary report.

A collection of high-precision tiltmeters is being operated at Pinon Flat Observatory, southern California, both to compare instruments and to measure tectonic deformation. We report on 1.2 years of data from four of these: two Michelson-Gale long fluid tiltmeters, one long center-pressure tiltmeter, and a shallow borehole tiltmeter. The three long-base instruments are all located on the same baseline, with a precise leveling line running between their end-monuments. At nontidal frequencies, only the two Michelson-Gale instruments show some coherence (gamma 2 = .3 for periods of 2 to 4 days), while the center-pressure instrument is correlated with air temperature at periods from a few days to a few weeks. The most stable tilt record shows a secular rate of 0.28 mu rad/a, which may be real. Over much longer times, leveling to specially stabilized bench-marks should confirm this. Comparing instruments has identified more and less successful measurement techniques; it appears that low-noise data will most probably be produced only by relatively complex and expensive instruments, though even for these, the operating costs over any reasonable lifetime will exceed the capital cost. Even the best existing sensors must be improved to measure continuous tectonic motions.

Disasters↗
PubMed1984

An evaluation of two antenatal information booklets.

The readability of two antenatal education books which are widely distributed to expectant mothers was assessed. There were some significant differences, and it was anticipated that this would be reflected in the levels of information imparted to the mothers, particularly when they were analysed by social class. In practice the differences were small, and the only one of significance was that the book which was believed to be more readable and more attractive in format resulted in higher knowledge scores in social classes I and II, but not in social classes III to V. Possible explanations for this are discussed. Clear benefit in terms of knowledge was demonstrated when mothers received a book in advance of their attendance at the antenatal booking clinic. They arrived better prepared and better informed, with knowledge to help the healthy development of the foetus at an early stage in pregnancy. The additional postage costs in sending out booklets is considered justifiable.

Evaluation Studies as Topic↗
PubMed1982

The atmosphere of Titan.

The discovery that Titan had an atmosphere was made by the identification of methane in the satellite's spectrum in 1944. But the abundance of this gas and the identification of other major constituents required the 1980 encounter by the Voyager 1 spacecraft. in the intervening years, traces of C2H2, C2H4, C2H6 and CH3D had been posited to interpret emission bands in Titan's IR spectrum. The Voyager infrared Spectrometer confirmed that these gases were present and added seven more. The atmosphere is now known to be composed primarily of molecular nitrogen. But the derived mean molecular weight suggests the presence of a significant amount of some heavier gas, most probably argon. It is shown that this argon must be primordial, and that one can understand the evolution of Titan's atmosphere in terms of degassing of a mixed hydrate dominated by CH4, N2 and 36Ar. This model satisfactorily explains the absence of neon and makes no special requirements on the satellite's surface temperature. The organic chemistry taking place on Titan today invites comparison with chemical evolution on the primitive Earth prior to the origin of life.

Biological Evolution↗
PubMed1979

The Martian atmosphere: some unanswered questions.

The study of the Martian atmosphere and its significance for the possible origin of life on Mars is still very incomplete. Further investigations are needed to define the total volatile inventory, the early history of the atmosphere, and the relationship of the atmosphere to the question of indigenous life. In addition, studies of Venus, comets, and the Jupiter system will add significantly to our abilities to understand the early history of Mars.

Carbon↗
PubMed1975

Effects of low temperatures on microtubules in the non-myelinated axons of post-ganglionic sympathetic nerves.

The effect of temperature changes on the number of microtubules in non-myelinated axons has been studied in cat inferior mesenteric ganglion/hypogastric nerve preparations incubated at various temperatures in Eagles minimal essential tissue culture medium in vitro. At 37 degrees C the non-myelinated axons contained 28.4 plus or minus 0.8 S.E.M. (54) microtubules per axon. After incubation at 0 degrees C for 4 h this number fell to 2.3 plus or minus 0.1 S.E.M. (41) but returned to normal levels when the nerves were rewarmed. This loss of microtubules on cooling the nerves and their reappearance on rewarming was a rapid process; it was independent of the influence of the nueronal cell body and of protein synthesis within the axon. The preservation of the microtubules was improved when D2O was present in the incubation medium. Reformed microtubules appeared to function normally with respect to their possible role in the transport of noradrenaline storage vesicles along the axons.

Animals↗
PubMedDate not supplied

Time travel and chemical evolution: a look at the outer solar system.

Many space scientists think that the chemical conditions today on planets and moons of the outer solar system are similar to conditions on Earth soon after it formed. If so, we can learn much about the chemistry that led to life on this planet. We can also speculate about exotic habitats that might have given rise to other types of life. And if we are able to discern the chemical reactions now occurring in the outer solar system, we may be able to extrapolate these rules to other solar systems, and so define the habitable zones around other stars where the potential for life is high.

Chemical Phenomena↗