Using ultra-thin parylene films as an organic gate insulator in nanowire field-effect transistors

We report the development of nanowire field-effect transistors featuring an ultra-thin parylene film as a polymer gate insulator. The room temperature, gas-phase deposition of parylene is an attractive alternative to oxide insulators prepared at high temperatures using atomic layer deposition. We discuss our custom-built parylene deposition system, which is designed for reliable and controlled deposition of <100 nm thick parylene films on III-V nanowires standing vertically on a growth substrate or horizontally on a device substrate. The former case gives conformally-coated nanowires, which we used to produce functional $\Omega$-gate and gate-all-around structures. These give sub-threshold swings as low as 140 mV/dec and on/off ratios exceeding $10^3$ at room temperature. For the gate-all-around structure, we developed a novel fabrication strategy that overcomes some of the limitations with previous lateral wrap-gate nanowire transistors. Finally, we show that parylene can be deposited over chemically-treated nanowire surfaces; a feature generally not possible with oxides produced by atomic layer deposition due to the surface `self-cleaning' effect. Our results highlight the potential for parylene as an alternative ultra-thin insulator in nanoscale electronic devices more broadly, with potential applications extending into nanobioelectronics due to parylene's well-established biocompatible properties

Biases in Cometary Catalogues and Planet X

Two sets of investigators -- Murray (1999) and Matese, Whitman & Whitmire (1999) -- have recently claimed evidence for an undiscovered Solar System planet from possible great circle alignments in the aphelia directions of the long period comets. However, comet discoveries are bedevilled by selection effects. These include anomalies caused by the excess of observers in the northern as against the southern hemisphere, seasonal and diurnal biases, directional effects which make it harder to discover comets in certain regions of the sky, as well as sociological biases. The stream proposed by Murray is shown on an equal area Hammer-Aitoff projection. The addition of newer data weakens the case for the alignment. There is also evidence that the subsample in the stream is affected by seasonal and north-south biases. The stream proposed by Matese et al. is most obvious in the sample of dynamically new comets, and especially in those whose orbits are best known. The most recent data continues to maintain the overpopulation in this great circle. This pattern in the data occurs about once in a thousand times by chance. Numerical integrations are used to demonstrate that a planet by itself can reduce the perihelia of comets in its orbital plane to sufficiently small values so that they could be discovered from the Earth. There is a need for a sample of long period comets that is free from unknown or hard-to-model selection effects. Such will be provided by the European Space Agency satellite GAIA.Comment: 16 pages, 14 figures, MNRAS in pres

Thermodynamics of a black hole in a cavity

We present a unified thermodynamical description of the configurations consisting on self-gravitating radiation with or without a black hole. We compute the thermal fluctuations and evaluate where will they induce a transition from metastable configurations towards stable ones. We show that the probability of finding such a transition is exponentially small. This indicates that, in a sequence of quasi equilibrium configurations, the system will remain in the metastable states till it approaches very closely the critical point beyond which no metastable configuration exists. Near that point, we relate the divergence of the local temperature fluctuations to the approach of the instability of the whole system, thereby generalizing the usual fluctuations analysis in the cases where long range forces are present. When angular momentum is added to the cavity, the above picture is slightly modified. Nevertheless, at high angular momentum, the black hole loses most of its mass before it reaches the critical point at which it evaporates completely.Comment: 27 pages, latex file, contains 3 figures available on request at [email protected]

Quality of life, coping strategies and support needs of women seeking Traditional Chinese Medicine for infertility and viable pregnancy in Australia: a mixed methods approach

Extent: 11p.Background: Infertility affects about 15% of couples in Western-societies with most progressing to fertility clinics for treatment. Despite being common, infertility is often experienced as a lonely road for affected couples. In this paper we expand on our previously published findings of women’s experiences with infertility or difficulty of viable pregnancy who had sought Traditional Chinese Medicine (TCM) therapy in Australia, and focus on women’s quality of life, coping strategies, and support needs. Methods: We applied mixed methods using the Tuebingen Quality of Life and the COPE questionnaires and in-depth interviews with 25 women with primary or secondary infertility, recurrent miscarriages or unexplained stillbirth, and who had consulted a TCM practitioner. We used a thematic approach to analyse the interviews, and descriptive statistics to evaluate questionnaire responses. Results: Women reported through both questionnaires and interviews compromised quality of life due to the high level of distress, guilt, grief, and frustration caused by infertility. However, our women represented a highly motivated sample, actively seeking alternative support. While the TCM approach to infertility management increased women’s sense of personal agency and control through education and continuity of care, the need for greater understanding and support on a societal level remains. Conclusions: In infertility, ongoing emotional and instrumental support is pivotal to the wellbeing and quality of life of the affected. Traditional Chinese Medicine addresses some support needs in infertility not routinely available in the Western model of care. More peer-led and professional-led support groups are greatly needed for women experiencing infertility to help break isolation and raise awareness of integrative approaches to fertility management.Karin Ried and Ann Alfre

Astrophysics in 2005

We bring you, as usual, the Sun and Moon and stars, plus some galaxies and a new section on astrobiology. Some highlights are short (the newly identified class of gamma-ray bursts, and the Deep Impact on Comet 9P/ Tempel 1), some long (the age of the universe, which will be found to have the Earth at its center), and a few metonymic, for instance the term "down-sizing" to describe the evolution of star formation rates with redshift