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Biomedical subjects

T Owen

Publications and source records attributed to T Owen.

At least 19 recordsLinked to original sources
PubMed2005

Complex organic matter in Titan's atmospheric aerosols from in situ pyrolysis and analysis.

Aerosols in Titan's atmosphere play an important role in determining its thermal structure. They also serve as sinks for organic vapours and can act as condensation nuclei for the formation of clouds, where the condensation efficiency will depend on the chemical composition of the aerosols. So far, however, no direct information has been available on the chemical composition of these particles. Here we report an in situ chemical analysis of Titan's aerosols by pyrolysis at 600 degrees C. Ammonia (NH3) and hydrogen cyanide (HCN) have been identified as the main pyrolysis products. This clearly shows that the aerosol particles include a solid organic refractory core. NH3 and HCN are gaseous chemical fingerprints of the complex organics that constitute this core, and their presence demonstrates that carbon and nitrogen are in the aerosols.

Aerosols↗
PubMed2004

Knowledge, attitudes and behaviour in the sun: the barriers to behavioural change in Northern Ireland.

To inform future health promotion programmes, we studied the knowledge, attitudes and behaviour of the Northern Ireland population to sun care. An interviewer-administered questionnaire was applied to one adult per household from a random sample of 1242 addresses. Lower levels of knowledge were found among respondents who were male, aged under 25 years or over 65 years, in a manual occupation or living in the west where health promotion activity on this topic was less active than in the east. Younger adults, females and professional groups were more likely to indicate that a suntan was important, healthy or attractive. Use of high factor sunscreen was inversely proportional to perceived importance of a suntan. Sunburn was more common in younger adults but more men reported multiple episodes of burning. Regular skin checks were uncommon and self-assessment of skin type was unrealistic indicating that sun care advice based on self assessment should be avoided in this population. Future campaigns should target appropriate messages at specific population subgroups. The study highlights the importance of collecting baseline information before implementing health promotion programmes and suggests that repeat monitoring is essential to ensure that key messages remain relevant. This study also indicates that Care in the Sun campaigns here impacted on general awareness in the population even with limited resources. There is, therefore, potential for greater impact with high funding levels.

Adolescent↗
PubMed1999

A low-temperature origin for the planetesimals that formed Jupiter.

The four giant planets in the Solar System have abundances of 'metals' (elements heavier than helium), relative to hydrogen, that are much higher than observed in the Sun. In order to explain this, all models for the formation of these planets rely on an influx of solid planetesimals. It is generally assumed that these planetesimals were similar, if not identical, to the comets from the Oort cloud that we see today. Comets that formed in the region of the giant planets should not have contained much neon, argon and nitrogen, because the temperatures were too high for these volatile gases to be trapped effectively in ice. This means that the abundances of those elements on the giant planets should be approximately solar. Here we show that argon, krypton and xenon in Jupiter's atmosphere are enriched to the same extent as the other heavy elements, which suggests that the planetesimals carrying these elements must have formed at temperatures lower than predicted by present models of giant-planet formation.

Cold Temperature↗
PubMed1999

An experimental study of the isotopic enrichment in Ar, Kr, and Xe when trapped in water ice.

The isotopic enrichment of argon, krypton, and xenon, when trapped in water ice, was studied experimentally. The isotopes were found to be enriched according to their (m1/m2)1/2 ratio. These enrichment factors could be useful for comparison among the uncertain cosmic or solar isotopic ratios, the hopeful in situ cometary ratio, and those in Earth's atmosphere, in the context of cometary delivery of volatiles to Earth.

Argon↗
PubMed1998

Transient clouds in Titan's lower atmosphere.

The 1980 encounter by the Voyager 1 spacecraft with Titan, Saturn's largest moon, revealed the presence of a thick atmosphere containing nitrogen and methane (1.4 and approximately 0.05 bar, respectively). Methane was found to be nearly saturated at Titan's tropopause, which, with other considerations, led to the hypothesis that Titan might experience a methane analogue of Earth's vigorous hydrological cycle, with clouds, rain and seas. Yet recent analyses of Voyager data indicate large areas of super-saturated methane, more indicative of dry and stagnant conditions. A resolution to this apparent contradiction requires observations of Titan's lower atmosphere, which was hidden from the Voyager cameras by the photochemical haze (or smog) in Titan's stratosphere. Here we report near-infrared spectroscopic observations of Titan within four narrow spectral windows where the moon's atmosphere is ostensibly transparent. We detect pronounced flux enhancements that indicate the presence of reflective methane condensation clouds in the troposphere. These clouds occur at a relatively low altitude (15+/-10 km), at low latitudes, and appear to cover approximately 9 per cent of Titan's disk.

Atmosphere↗
PubMed1998

Estrogen receptor-alpha is developmentally regulated during osteoblast differentiation and contributes to selective responsiveness of gene expression.

Estrogen responsiveness of bone is a fundamental regulatory mechanism operative in skeletal homeostasis. We examined the expression of estrogen receptor-alpha (ER) messenger RNA (mRNA) in cultured rat calvarial-derived osteoblasts during progressive development of the osteoblast phenotype. Levels of ER message were compared with the expression of traditional osteoblastic markers that have been mapped throughout the differentiation process of these cells. ER transcripts, measured using semiquantitative RT-PCR analysis, were expressed at low levels in early stage proliferating osteoblasts and increased at confluence upon initial expression of bone cell phenotypic genes. A 23-fold up-regulation of ER mRNA expression coincided with the initiation of alkaline phosphatase activity (day 8). ER mRNA levels progressively increased 70-fold, reaching a maximum level on days 22-25 in fully differentiated osteoblasts when osteocalcin expression peaked, but declined precipitously by day 32 in osteocytic cells. Analysis of RNA isolated directly from rat calvaria confirmed these in vitro results and demonstrated that ER message levels become more abundant postnatally as bone becomes more mineralized. We also examined the responsiveness of osteoblasts to 17beta-estradiol (17beta-E2) at two periods of maturation: the nodule-forming stage (day 14) and the late mineralization stage (day 30). Estradiol suppressed the levels of alkaline phosphatase, osteocalcin, osteonectin, and ER mRNAs on day 14, but up-regulated these messages on day 30. In contrast, 17beta-E2 treatment regulated the steady state levels of transforming growth factor-beta1 and type I procollagen mRNAs only in the late mineralization stage, whereas histone H4 message was unaffected by the steroid at either stage of differentiation. Thus, the observed developmental expression of ER mRNA correlates with progressive osteoblast differentiation and may be a contributing factor to differential regulation of bone cell gene expression by 17beta-E2.

Animals↗
PubMed1997

Measurements of 12C/13C, 14N/15N, and 32S/34S ratios in comet Hale-Bopp (C/1995 O1).

The 12C/13C, 14N/15N, and 32S/34S isotope ratios in comet Hale-Bopp (C/1995 O1) were determined through observations taken with the James Clerk Maxwell Telescope. Measurements of rare isotopes in HCN and CS revealed isotope ratios of H12CN/H13CN = 111 +/- 12, HC14N/HC15N = 323 +/- 46, and C32S/C34S = 27 +/- 3. Within the measurement uncertainties, the isotopic ratios are consistent with solar system values. The cometary volatiles thus have an origin in the solar system and show no evidence for an interstellar component.

Carbon↗
PubMed1997

Titan and the origin of life on Earth.

The relevance of Titan to the study of pre-biotic chemistry and the origin of life on Earth will be addressed by an interdisciplinary group of Cassini/Huygens scientists using the different, but synergistic data sets obtained by NASA's Cassini Orbiter and ESA's Huygens Probe. Titan's special importance lies in the primitive chemically-reducing nature of its atmosphere Cassini/ Huygens instruments will determine what compounds form in this environment, and the results will be compared with models for pre-biological chemical evolution on Earth.

Atmosphere↗
PubMed1997

The impact of heart health promotion on coronary heart disease lifestyle risk factors in schoolchildren: lessons learnt from a community-based project.

A community health promotion project called Action Heart was undertaken in two electoral wards in Rotherham to try to change lifestyles of people. Schools were included within the project. Coronary heart disease lifestyle risk factors were measured at baseline and after a three year period in the intervention area and a similar control area. Lifestyle factors in schoolchildren were measured separately from adults using a different instrument. The post intervention survey of adults and economic evaluation demonstrated that Action Heart had achieved cost-effective estimated health gains. In the schoolchildren however, a mixture of positive and negative risk factor changes in both areas was demonstrated. Significant changes in lifestyle risk factors in schoolchildren were not elicited using this approach. The possible reasons for the lack of impact on lifestyle risk factors in schoolchildren are examined and the implications for further work explored.

Adolescent↗
PubMed1996

Comets, meteorites and atmospheres.

The relatively low value of Xe/Kr in the atmospheres of Earth and Mars seems to rule out meteorites as the major carriers of noble gases to the inner planets. Laboratory experiments on the trapping of gases in ice forming at low temperatures suggest that comets may be a better choice. It is then possible to develop a model for the origin of inner planet atmospheres based on volatiles delivered by comets added to volatiles originally trapped in planetary rocks. The model will be tested by results from the Galileo Entry Probe.

Argon↗
PubMed1995

Comets, impacts, and atmospheres.

We are proposing a model for the delivery of volatiles to the inner planets by icy planetesimals (comets). Laboratory studies of the trapping of gases in ice forming at low temperatures simulate the formation of comet nuclei at various distances from the Sun in the solar nebula. The total gas content as well as the relative proportions of gases trapped in the ice are strong functions of temperature. As they trap N2 inefficiently, all planetesimals formed interior to Neptune are deficient in nitrogen, acquiring values of C/N resembling those found in the inner planet volatile inventories. A mixture of three basic types of comets appears capable of accounting for the observed volatile inventories on Venus, Earth, and Mars, with the caveat that impact erosion is necessary to explain the present condition of the martian atmosphere. The model includes the possibility of several epochs of clement conditions on early Mars. Some tests of these ideas are suggested, including measurements in Jupiter's atmosphere by the Galileo probe.

Atmosphere↗
PubMed1995

Dark matter in the outer solar system.

There are now a large number of small bodies in the outer solar system that are known to be covered with dark material. Attempts to identify that material have been thwarted by the absence of discrete absorption features in the reflection spectra of these planetesimals. An absorption at 2.2 micrometers that appeared to be present in several objects has not been confirmed by new observations. Three absorptions in the spectrum of the unusually red planetesimal 5145 Pholus are well-established, but their identity remains a mystery.

Astronomy↗
PubMed1995

Who should give lifestyle advice in general practice and what factors influence attendance at health promotion clinics? Survey of patients' views.

BACKGROUND: Health promotion activity in general practice has increased greatly since 1990. A large proportion of this work is undertaken by practice nurses. Little is known about patients' views about the providers of health promotion or their views about general practice health promotion clinics. AIM: A study was carried out in 1992 to determine patients' views about the provision of health promotion advice by general practitioners and practice nurses and their views about attending health promotion clinics. METHOD: A postal questionnaire was sent to a random sample of 1750 patients aged 16 years and over from five general practices in south Tyneside. The questionnaire explored patients' preferences regarding health promotion advice from the general practitioner or practice nurse in relation to four areas of lifestyle advice and factors that might encourage patients to attend a health promotion clinic. RESULTS: A response rate of 75% was obtained from 1639 eligible patients. Receiving health promotion advice from either the general practitioner or the practice nurse was the most commonly preferred option expressed by patients overall. The ability of health promotion clinic staff to deal with patients' concerns about their illness and short waiting times were more likely to influence patients' attendance at health promotion clinics than the presence of a general practitioner or practice nurse. CONCLUSION: In the present study, many patients found health advice received from practice nurses and general practitioners equally acceptable. However, it was the ability of health professionals to respond to patients' health concerns in the health promotion clinic rather than the type of health professional running the clinic that was important for patients.

Adolescent↗
PubMed1994

Near-infrared spectroscopy of dark asteroids.

Near-infrared (J, H and K bands) spectra of nine dark asteroids (chosen among a sample of supposed primitive objects between C and D classes) have been obtained at the Mauna Kea Observatory (Hawaii) with the 2.2-m telescope using KSPEC as spectrograph. The aim of this work was to search for evidence of the presence of organic materials in these objects as found in other planetary bodies as 5145 Pholus, and in some cometary nuclei. A careful analysis of the data has revealed flat or slightly redder spectra than the solar one for all observed asteroids. No evidence of distinct absorption features was found.

Astronomy↗
PubMed1994

The search for other planets: clues from the solar system.

Studies of element abundances and values of D/H in the atmospheres of the outer planets and Titan support a two-step model for the formation of these bodies. This model suggests that the dimensions of Uranus provide a good index for the sensitivity required to detect planets around other stars. The high proportion of N2 on the surfaces of Pluto and Triton indicates that this gas was the dominant reservoir of nitrogen in the early solar nebula. It should also be abundant on pristine comets. There is evidence that some of these comets may well have brought a large store of volatiles to the inner planets, while others were falling into the sun. In other systems, icy planetesimals falling into stars should reveal themselves through high values of D/H.

Astronomical Phenomena↗
PubMed1994

Fractionated martian atmosphere in the nakhlites?

Considerable evidence points to a martian origin of the SNC meteorites. Noble gas isotopic compositions have been measured in most SNC meteorites. The 129Xe/132Xe vs, 84Kr/132Xe ratios in Chassigny, most shergottites, and lithology C of EETA 79001 define a linear array. This array is thought to be a mixing line between martian mantle and martian atmosphere. One of the SNC meteorites, Nakhla, contains a leachable component that has an elevated 129Xe/132Xe ratio relative to its 84Kr/132Xe ratio when compared to this approximately linear array. The leachable component probably consists in part of iddingsite, an alteration product produced by interaction of olivine with aqueous fluid at temperatures lower than 150 degrees C. The elevated Xe isotopic ratio may represent a distinct reservoir in the martian crust or mantle. More plausibly, it is elementally fractionated martian atmosphere. Formation of sediments fractionates the noble gases in the correct direction. The range of sediment/atmosphere fractionation factors is consistent with the elevated 129Xe/132Xe component in Nakhla being contained in iddingsite, a low temperature weathering product. The crystallization age of Nakhla is 1.3 Ga. Its low-shock state suggests that it was ejected from near the surface of Mars. As liquid water is required for the formation of iddingsite, these observations provide further evidence for the near surface existence of aqueous fluids on Mars more recently than 1.3 Ga.

Atmosphere↗