18,461 research outputs found
Vehicle Steering control: A model of learning
A hierarchy of strategies were postulated to describe the process of learning steering control. Vehicle motion and steering control data were recorded for twelve novices who drove an instrumented car twice a week during and after a driver training course. Car-driver describing functions were calculated, the probable control structure determined, and the driver-alone transfer function modelled. The data suggested that the largest changes in steering control with learning were in the way the driver used the lateral position cue
Water ice in the Kuiper belt
We examine a large collection of low-resolution near-infrared spectra of Kuiper Belt objects (KBOs) and centaurs in an attempt to understand the presence of water ice in the Kuiper Belt. We find that water ice on the surface of these objects occurs in three separate manners: (1) Haumea family members uniquely show surfaces of nearly pure water ice, presumably a consequence of the fragmentation of the icy mantle of a larger differentiated proto-Haumea; (2) large objects with absolute magnitudes of H < 3 (and a limited number to H = 4.5) have surface coverings of water iceāperhaps mixed with ammoniaāthat appears to be related to possibly ancient cryovolcanism on these large objects; and (3) smaller KBOs and centaurs which are neither Haumea family members nor cold-classical KBOs appear to divide into two families (which we refer to as "neutral" and "red"), each of which is a mixture of a common nearly neutral component and either a slightly red or very red component that also includes water ice. A model suggesting that the difference between neutral and red objects due to formation in an early compact solar system either inside or outside, respectively, of the ~20 AU methanol evaporation line is supported by the observation that methanol is only detected on the reddest objects, which are those which would be expected to have the most of the methanol containing mixture
Modulation of individual components of gastric motor response to duodenal glucose
AIM: To evaluate individual components of the antro-pyloro-duodenal (APD) motor response to graded small intestinal glucose infusions in healthy humans. METHODS: APD manometry was performed in 15 healthy subjects (12 male; 40 Ā± 5 years, body mass index 26.5 Ā± 1.6 kg/m2) during four 20-min intraduodenal infusions of glucose at 0, 0.5, 1.0 and 1.5 kcal/min, in a randomised double-blinded fashion. Glucose solutions were infused at a rate of 1 mL/min and separated by 40-min āwash-outā period. Data are mean Ā± SE. Inferential analyses are repeated measure analysis of variance with Bonferroni post-hoc testing. RESULTS: At 0 kcal/min frequency of pressure waves were: antrum (7.5 Ā± 1.8 waves/20 min) and isolated pyloric pressure waves (IPPWs) (8.0 Ā± 2.3 waves/20 min) with pyloric tone (0.0 Ā± 0.9 mmHg). Intraduodenal glucose infusion acutely increased IPPW frequency (P < 0.001) and pyloric tone (P = 0.015), and decreased antral wave frequency (P = 0.007) in a dose-dependent fashion. A threshold for stimulation was observed at 1.0 kcal/min for pyloric phasic pressure waves (P = 0.002) and 1.5 kcal/min for pyloric tone and antral contractility. CONCLUSION: There is hierarchy for the activation of gastrointestinal motor responses to duodenal glucose infusion. An increase in IPPWs is the first response observed.Adam M Deane, Laura K Besanko, Carly M Burgstad, Marianne J Chapman, Michael Horowitz, Robert JL Frase
Plasma Sterilization Technology for Spacecraft Applications
The application of plasma gas technology to sterilization and decontamination of spacecraft components is considered. Areas investigated include: effective sterilizing ranges of four separate gases; lethal constituents of a plasma environment; effectiveness of plasma against a diverse group of microorganisms; penetrating efficiency of plasmas for sterilization; and compatibility of spacecraft materials with plasma environments. Results demonstrated that plasma gas, specifically helium plasma, is a highly effective sterilant and is compatible with spacecraft materials
Obituary: Arthur Cruickshank 1932 - 2011. A native Gondwanan, who studied the former continent's fossil tetrapods
Dr Arthur Richard Ivor Cruickshank died
on 4th December 2011, aged 79, in the
Borders General Hospital, Melrose, Scotland.
Arthur Cruickshank was part of the post-war
generation of palaeontologists who laid the
foundations on which todayās researchers
build. Appropriately for someone from
an expatriate Scots family living in Kenya,
much of his work was on the extinct reptiles
of the great southern palaeocontinent of
Gondwana
Xwnt-5A: a maternal Wnt that affects morphogenetic movements after overexpression in embryos of Xenopus laevis
To contribute to an understanding of the roles and mechanisms of action of Wnts in early vertebrate development, we have characterized the normal expression of Xenopus laevis Wnt-5A, and investigated the consequences of misexpression of this putative signalling factor. Xwnt-5A transcripts are expressed throughout development, and are enriched in both the anterior and posterior regions of embryos at late stages of development, where they are found primarily in ectoderm, with lower levels of expression in mesoderm. Overexpression of Xwnt-5A in Xenopus embryos leads to complex malformations distinct from those achieved by ectopic expression of Xwnts ā1, ā3A, or ā8. This phenotype is unlikely to result from Xwnt-5A acting as an inducing agent, as overexpression of Xwnt-5A does not rescue dorsal structures in UV-irradiated embryos, does not induce mesoderm in blastula caps, and Xwnt-5A does not alter the endogenous patterns of expression of goosecoid, Xbra, or Xwnt-8. To pursue whether Xwnt-5A has the capacity to affect morphogenetic movements, we investigated whether overexpression of Xwnt-5A alters the normal elongation of blastula cap explants induced by activin. Intriguingly, Xwnt-5A blocks the elongation of blastula caps in response to activin, without blocking the differentiation of either dorsal or ventral mesoderm within these explants. The data are consistent with Xwnt-5A having the potential activity of modifying the morphogenetic movements of tissues
Full Scale Proton Beam Impact Testing of new CERN Collimators and Validation of a Numerical Approach for Future Operation
New collimators are being produced at CERN in the framework of a large
particle accelerator upgrade project to protect beam lines against stray
particles. Their movable jaws hold low density absorbers with tight geometric
requirements, while being able to withstand direct proton beam impacts. Such
events induce considerable thermo-mechanical loads, leading to complex
structural responses, which make the numerical analysis challenging. Hence, an
experiment has been developed to validate the jaw design under representative
conditions and to acquire online results to enhance the numerical models. Two
jaws have been impacted by high-intensity proton beams in a dedicated facility
at CERN and have recreated the worst possible scenario in future operation. The
analysis of online results coupled to post-irradiation examinations have
demonstrated that the jaw response remains in the elastic domain. However, they
have also highlighted how sensitive the jaw geometry is to its mounting support
inside the collimator. Proton beam impacts, as well as handling activities, may
alter the jaw flatness tolerance value by 70 m, whereas the
flatness tolerance requirement is 200 m. In spite of having validated
the jaw design for this application, the study points out numerical limitations
caused by the difficulties in describing complex geometries and boundary
conditions with such unprecedented requirements.Comment: 22 pages, 17 figures, Prepared for submission to JINS
News coverage of suicidal behaviour in the United Kingdom and the Republic of Ireland
Background: Media reporting of suicide has been associated with imitative acts. Internationally, this has led to the development of guidelines to promote responsible reporting of suicide.
Aims: To examine the nature and quality of news coverage of suicidal behaviour in the United Kingdom (UK) and Republic of Ireland (ROI).
Method: UK and ROI press clippings relating to suicide over 12 months (N=8101) were coded for content and assessed for quality against existing guidelines. We examined variability in relation to key characteristics (e.g. type of publication) and compared newspaper portrayal of suicide against official statistics.
Results: Reports were biased towards young, female and relatively unusual suicides (including those involving a celebrity, more than one individual and violent methods). Almost a third of reports had inappropriate headlines, but only a minority was of poor overall quality, and editors appear to be responsive to feedback. There was considerable variability in the quality of reports for different suicide methods.
Limitations: This work cannot account for the impact of reporting on suicidal behaviour. The speed of change in media trends also limits its conclusions.
Conclusion: Our findings underscore the need for sustained efforts to promote responsible reporting of suicide
- ā¦