606 research outputs found
A Feasibility Study of Liquid Sterile Insertion
Technique for sterile insertion of liquids into previously sterilized spacecraf
The Royal Fine Art Commission and 75 years of English design review: the final 15 years, 1984–1999
This paper is the second of two linked papers that focus on the work of the Royal Fine Art Commission (RFAC), which for three quarters of a century held the mantel of the UK Government’s advisor on design in the built environment. This paper tells the story of the organization’s final 15 years when, under a new and charismatic leader, the Commission substantially changed its modus operandi, and came out of the shadows, although without ever fully embracing the modern era of government. Analysis of the archives are supplemented by what the limited available literature tells us about the RFAC and by a small number of interviews with key stakeholders with first-hand experience of the operation of the RFAC; those who either worked for it, were responsible for it within Government, or were reviewed by it. The experience offers valuable insights into the practices and problematics of design governance that today, internationally, forms one of the keystones of modern day planning
Pulse generation without gain-bandwidth limitation in a laser with self-similar evolution
With existing techniques for mode-locking, the bandwidth of ultrashort pulses from a laser is determined primarily by the spectrum of the gain medium. Lasers with self-similar evolution of the pulse in the gain medium can tolerate strong spectral breathing, which is stabilized by nonlinear attraction to the parabolic self-similar pulse. Here we show that this property can be exploited in a fiber laser to eliminate the gain-bandwidth limitation to the pulse duration. Broad (̃200 nm) spectra are generated through passive nonlinear propagation in a normal-dispersion laser, and these can be dechirped to ̃20-fs duration
Survival of bacterial isolates exposed to simulated Jovian trapped radiation belt electrons and solar wind protons
With missions to Jupiter, the spacecraft will be exposed for extended duration to solar wind radiation and the Jovian trapped radiation belt. This study is designed to determine the effect of these radiation environments on spacecraft bacterial isolates. The information can be used in the probability of contamination analysis for these missions. A bacterial subpopulation from Mariner Mars 1971 spacecraft (nine sporeforming and three nonsporeforming isolates) plus two comparative organisms, Staphylococcus epidermidis ATCC 17917 and a strain of Bacillus subtilis var. niger, were exposed to 2-, 12-, and 25-MeV electrons at different doses with simultaneous exposure to a vacuum of 0.0013 N/sqm at 20 and -20 C. The radioresistance of the subpopulation was dependent on the isolate, dose, and energy of electrons. Temperature affected the radioresistance of only the sporeforming isolates. Survival data indicated that spores were reduced approximately 1 log/1500 J/kg, while nonsporeforming isolates (micrococci) were reduced 1.5 to 2 logs/1500 J/kg with the exception of an apparent radioresistant isolate whose resistance approached that of the spores. The subpopulation was found to be less resistant to lower energy than to higher energy electrons
Band structure approach to the resonant x-ray scattering
We study the resonance behaviour of the forbidden 600 and 222 x-ray Bragg
peaks in Ge using LDA band structure methods. These Bragg peaks remain
forbidden in the resonant dipole scattering approximation even taking into
account the non local nature of the band states. However they become allowed at
resonance if the eigenstates of the unoccupied conduction band involve a
hybridization of p like and d like atomic states. We show that the energy
dependence of the resonant behaviour, including the phase of the scattering, is
a direct measure of this p-d hybridization.and obtain quantitative agreement
with experiment. A simple physical picture involving a product of dipole and
quadrupolar transition matrix elements explains this behaviour and shows that
it should be generally true for cases where the resonating atom is not at an
inversion center. This has strong implications for the description of the
resonance behavior of x-ray scattering in materials where the resonant atom is
not at an inversion center such as V2O3 and in ferro and antiferro electric and
piezo electric materials in general.Comment: 4 pages, 5figure
Synthetic biology and biomass conversion: a match made in heaven?
To move our economy onto a sustainable basis, it is essential that we find a replacement for fossil carbon as a source of liquid fuels and chemical industry feedstocks. Lignocellulosic biomass, available in enormous quantities, is the only feasible replacement. Many micro-organisms are capable of rapid and efficient degradation of biomass, employing a battery of specialized enzymes, but do not produce useful products. Attempts to transfer biomass-degrading capability to industrially useful organisms by heterologous expression of one or a few biomass-degrading enzymes have met with limited success. It seems probable that an effective biomass-degradation system requires the synergistic action of a large number of enzymes, the individual and collective actions of which are poorly understood. By offering the ability to combine any number of transgenes in a modular, combinatorial way, synthetic biology offers a new approach to elucidating the synergistic action of combinations of biomass-degrading enzymes in vivo and may ultimately lead to a transferable biomass-degradation system. Also, synthetic biology offers the potential for assembly of novel product-formation pathways, as well as mechanisms for increased solvent tolerance. Thus, synthetic biology may finally lead to cheap and effective processes for conversion of biomass to useful products
High-impedance surface acoustic wave resonators
Because of their small size, low loss, and compatibility with magnetic fields
and elevated temperatures, surface acoustic wave resonators hold significant
potential as future quantum interconnects. Here, we design, fabricate, and
characterize GHz-frequency surface acoustic wave resonators with the potential
for strong capacitive coupling to nanoscale solid-state quantum systems,
including semiconductor quantum dots. Strong capacitive coupling to such
systems requires a large characteristic impedance, and the resonators we
fabricate have impedance values above 100 . We achieve such high
impedance values by tightly confining a Gaussian acoustic mode. At the same
time, the resonators also have low loss, with quality factors of several
thousand at millikelvin temperatures. These high-impedance resonators are
expected to exhibit large vacuum electric-field fluctuations and have the
potential for strong coupling to a variety of solid-state quantum systems
Rethinking employability: How students build on interest in a subject to plan a career
As universities prioritise employability, there is increased attention to promoting students’ career decidedness. In this mixed method, cross-sectional study we explore whether and how student interest in their academic subject affects their career decidedness. Using surveys of 428 undergraduates studying sciences in a UK university (60% F, average age=19.9) and case examples from follow-up interviews with 15 students, we examine students’ interest development and its relation to their career decidedness and their desire for meaningful, interesting work. Findings showed that most students who were studying science in university had a well-developed interest that had motivated their choice of programme, and their subject interest and career decidedness were linked. Regression analyses indicated that student interest in their subject was a significant predictor of career decidedness, mediated by students’ desire to pursue that interest in their career. Open-ended comments on the surveys suggested that decidedness was informed by coursework, proactive career exploration, work experience, interest, feasibility, and familial contacts. Interviews confirmed these factors and illustrated how they contributed to students’ career decidedness. We propose implications for academics and career counsellors who might help students refine their interest by considering connections between their academic subject, interest, and related career options. We argue that educators and policymakers need to reframe employability interventions and think beyond teaching students skills or attributes that lead to employment. Educators can start with students’ interest in their subject and support students’ exploration of how they can continue to pursue that interest in various careers
Interaction-free measurement and forward scattering
Interaction-free measurement is shown to arise from the forward-scattered
wave accompanying absorption: a "quantum silhouette" of the absorber.
Accordingly, the process is not free of interaction. For a perfect absorber the
forward-scattered wave is locked both in amplitude and in phase. For an
imperfect one it has a nontrivial phase of dynamical origin (``colored
silhouette"), measurable by interferometry. Other examples of quantum
silhouettes, all controlled by unitarity, are briefly discussed.Comment: 4 pages in RevTex + 1 figure in eps; submitted to Phys. Rev. A since
09Jan98; now update
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