Empirical Limits on Radial Velocity Planet Detection for Young Stars

We report initial results from our long term search using precision radial velocities for planetary-mass companions located within a few AU of stars younger than the Sun. Based on a sample of >150 stars, we define a floor in the radial velocity scatter, sigma_RV, as a function of the chromospheric activity level R'_{HK}. This lower bound to the jitter, which increases with increasing stellar activity, sets the minimum planet mass that could be detected. Adopting a median activity-age relationship reveals the astrophysical limits to planet masses discernable via radial velocity monitoring, as a function of stellar age. Considering solar-mass primaries having the mean jitter-activity level, when they are younger than 100 / 300 / 1000 Myr, the stochastic jitter component in radial velocity measurements restricts detectable companion masses to > 0.3 / 0.2 / 0.1 M_Jupiter. These numbers require a large number -- several tens -- of radial velocity observations taken over a time frame longer than the orbital period. Lower companion mass limits can be achieved for stars with less than the mean jitter and/or with an increased number of observations.Comment: 5 pages, to appear the 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun proceedings edited by G. van Belle & H. Harri

Replacing Quantum Feedback with Open-Loop Control and Quantum Filtering

Feedback control protocols can stabilize and enhance the operation of quantum devices, however, unavoidable delays in the feedback loop adversely affect their performance. We introduce a quantum control methodology, combining open-loop control with quantum filtering, which is not constrained by feedback delays. For the problems studied (rapid purification and rapid measurement) we analytically derive lower bounds on the control performance that are comparable with the best corresponding bounds for feedback protocols.Comment: 5 pages, revtex4, 3 eps figures. Comments welcome. V2 minor corrections, published version

Burrowing apparatus

A soil burrowing mole is described in which a housing has an auger blade wound around a front portion. This portion is rotatable about a housing longitudinal axis relative to an externally finned housing rear portion upon operation of driving means to cause an advance through soil and the like. The housing carries a sensor sensitive to deviation from a predetermined path and to which is coupled means for steering the housing to maintain the path

Through the wall of literacy: transformative practice in social networks among GCSE re-sit further education students

Purpose The purpose of this paper is to explain how peripheral participants contributed to and became more central members of a community of practice based in a social network that was used to support mobile learning approaches among post-compulsory education students. The notion was that in inducing participation through pedagogical strategies, individualised online presence could be increased that would support studentship, confidence and literacy improvements in participants who are normally apprehensive about online and formal learning contexts. Design/methodology/approach The network was used by four separate groups of 16-19 aged students and 19+ aged adults, with a constant comparison made of their activity and communication. A content analysis was made of students’ posts to the network, with the codes sorted thematically to examine how students used the network to support themselves and each other. Interviews were held with students across the two years to explore perceptions of the network and the community. Findings Peripheral participants navigate through ontological thresholds online to develop individual identity presence online. Increased communicated actions (“posts”) improves participation overall and the interaction of members in terms of developing a community of practice online. The results of communicated actions posted in visible online spaces improved the literacy control and willingness to publish content created by those peripheral participants. Research limitations/implications The study is taken from a small sample (approx. 100 students) in a case study comparing results across four different groups in an English Further Education college. Most of the positive results in terms of an impact being made on their literacy capability was found among adult students, as opposed to students in two 16-19 aged groups. Research implications identify hypothetical stages of identity presence online for reluctant and peripheral participants. This shows the potential of students to be induced to openly participate in visible contexts that can support further identity development. Practical implications The implications show that blended learning is necessary to improve the opportunity for mobile learning to happen. Blended learning in itself is dependent on and simultaneously improves group cohesion of learners in online communities. When students develop a momentum of engagement (and residence within) networks they exploit further technological features and functions and become more co-operative as a group, potentially reducing teacher presence. Learning activities need to support the peripheral participants in discrete and purposeful ways, usually achieved through personalised supported learning tasks. The notion and attention paid to the difficulties in bringing peripheral participants online has implications for the prescription of online learning as a form of delivery, especially among FE students. Social implications This paper problematizes the notion of peripheral participants and suggests they are overlooked in consideration of learning delivery, design and environments. Peripheral participants may be considered to be students who are at risk of not being involved in social organisations, such as communities, and vulnerable to diminished support, for instance through the withdrawal of face-to-face learning opportunities at the expense of online learning. Originality/value This paper makes a small contribution to theories surrounding communities of practice and online learning. By deliberately focusing on a population marginalised in current educational debate, it problematizes the growing prescription of online learning as a mode of delivery by taking the perspectives and experiences of peripheral participants on board

Kinematic study of flight telerobotic servicer configuration issues

Several factors, such as body size and shape, and the number of arms and their placement, will influence how well the Flight Telerobotic Servicer (FTS) is suited to its potential duties for the Space Station Program. In order to examine the implications of these configuration options, eight specific 2, 3, and 4 armed FTS configuration were simulated and used to perform a Space Station Orbital Replacement Unit (ORU) exchange. The strengths and weaknesses of each configuration were evaluated. Although most of the configurations examined were able to perform the exchange, several of the 3 and 4 arm configurations had operational advantages. The results obtained form these simulations are specific to the assumptions associated with the ORU exchange scenario examined. However, they do illustrate the general interrelationships and sensitivities which need to be understood

Peptide Electrophoretic Patterns of Cucumoviruses

The peptide electrophoretic patterns of several cucumovirus isolates were compared using 15% polyacrylamide slab-gels. Both Staphylococcus aureus VB protease and a.-chymotrypsin partially digested the protein subunits of these virllies into peptides which produced different patterns when electrophoresed though the gels. Major differences were observed among peptide electrophoretic patterns of cucumber mosaic, peanut stunt and tomato aspermy viruses. Differences, if they do exist, among strains of the same virus were either in apparent or minor

PlantID – DNA-based identification of multiple medicinal plants in complex mixtures

Background An efficient method for the identification of medicinal plant products is now a priority as the global demand increases. This study aims to develop a DNA-based method for the identification and authentication of plant species that can be implemented in the industry to aid compliance with regulations, based upon the economically important Hypericum perforatum L. (St John’s Wort or Guan ye Lian Qiao). Methods The ITS regions of several Hypericum species were analysed to identify the most divergent regions and PCR primers were designed to anneal specifically to these regions in the different Hypericum species. Candidate primers were selected such that the amplicon produced by each species-specific reaction differed in size. The use of fluorescently labelled primers enabled these products to be resolved by capillary electrophoresis. Results Four closely related Hypericum species were detected simultaneously and independently in one reaction. Each species could be identified individually and in any combination. The introduction of three more closely related species to the test had no effect on the results. Highly processed commercial plant material was identified, despite the potential complications of DNA degradation in such samples. Conclusion This technique can detect the presence of an expected plant material and adulterant materials in one reaction. The method could be simply applied to other medicinal plants and their problem adulterants

Primary group size, social support, gender and future mental health status in a prospective study of people living in private households throughout Great Britain

Background. Structural characteristics of social networks such as primary group size have received less attention than measures of perceived social support. Previous research suggests that associations between social network size and later common mental disorder status may differ according to sex and initial mental state. Method. Adults participating in the 2000 British National Household Survey of psychiatric morbidity were randomly selected for follow-up 18 months later. The revised Clinical Interview Schedule (CIS-R) and the Interview Measure of Social Relations (IMSR) were administered at baseline and follow-up. Primary group size was defined as the total number of close relatives and friends. A four-level scale of common mental disorder was modelled with ordinal logistic regression, based on weighted data (n=2413). Findings. After adjusting for confounders, a primary group size of three or less at time 1 predicted worse mental health at time 2. This effect was greatest in men who were initially non-cases at baseline (averaged odds 4.5) and in women who were initially cases at baseline (average odds 2.9). Primary group size at time 2 was significantly predicted by level of common mental disorder at time 1 in women but not in men. Thus, confounding by baseline disorder does not explain risk of developing poor mental health in socially isolated men. Conclusion. This study replicates the strong effects of primary group size on future mental health that emerge when men and women are studied separately and when subjects are categorized according to baseline mental health status