7,624 research outputs found
Cryogenic propellant management: Integration of design, performance and operational requirements
The integration of the design features of the Shuttle elements into a cryogenic propellant management system is described. The implementation and verification of the design/operational changes resulting from design deficiencies and/or element incompatibilities encountered subsequent to the critical design reviews are emphasized. Major topics include: subsystem designs to provide liquid oxygen (LO2) tank pressure stabilization, LO2 facility vent for ice prevention, liquid hydrogen (LH2) feedline high point bleed, pogo suppression on the Space Shuttle Main Engine (SSME), LO2 low level cutoff, Orbiter/engine propellant dump, and LO2 main feedline helium injection for geyser prevention
Self-aligned fabrication process for silicon quantum computer devices
We describe a fabrication process for devices with few quantum bits (qubits),
which are suitable for proof-of-principle demonstrations of silicon-based
quantum computation. The devices follow the Kane proposal to use the nuclear
spins of 31P donors in 28Si as qubits, controlled by metal surface gates and
measured using single electron transistors (SETs). The accurate registration of
31P donors to control gates and read-out SETs is achieved through the use of a
self-aligned process which incorporates electron beam patterning, ion
implantation and triple-angle shadow-mask metal evaporation
Absorbent products for urinary/faecal incontinence: a comparative evaluation of key product designs
Background: The UK health service, nursing homes and public spend around ÂŁ94 million per year on incontinence pads (absorbent products) to contain urine and/or faeces, but the research base for making informed choices between different product designs is very weak.Objectives: The aim of this trial was to compare the performance and cost-effectiveness of the key absorbent product designs to provide a more solid basis for guiding selection and purchase.A further aim was to carry out the first stage in the development of a quality of life instrument for measuring the impact of absorbent product use on users' lives.Design: The work involved three clinical trials focusing on the three biggest market sectors. Each trial had a similar crossover design in which each participant tested all products within their group in random order.Settings, participants and methods: In Trial 1, 85 women with light urinary incontinence living in the community tested three products from each of the four design categories available (total of 12 test products): disposable inserts (pads); menstrual pads; washable pants with integral pad; and washable inserts. In Trial 2a, 85 moderate/heavily incontinent adults (urinary or urinary/faecal) living in the community (49 men and 36 women) tested three (or two) products from each of the five design categories available (total of 14 test products): disposable inserts (with mesh pants); disposable diapers (nappies); disposable pull-ups (similar to toddlers' trainer pants); disposable T-shaped diapers (nappies with waist-band); and washable diapers. All products were provided in a daytime and a (mostly more absorbent) night-time variant. In these first two trials, the test products were selected on the basis of data from pilot studies. In Trial 2b, 100 moderate/heavily incontinent adults (urinary or urinary/faecal) living in 10 nursing homes (27 men and 73 women) evaluated one product from each of the four disposable design categories from Trial 2a. Products were selected on the basis of product performance in Trial 2a and, again, daytime and night-time variants were provided. The first phase of work to develop a quality of life tool for measuring the impact of using different pad designs was carried out by interviewing participants from Trials 1 and 2a.Outcome measures: Product performance was characterised using validated questionnaires, which asked the participants (in Trials 1 and 2a) or carers (all participants in Trial 2b, except for the few who could report for themselves) to evaluate various aspects of pad performance (leakage, ease of putting on, discreetness, etc.) using a five-point scale (very goodâvery poor) at the end of the week (or 2 weeks for Trial 2b) of product testing. In addition, participants/carers were asked to save individual used pads in bags for weighing and to indicate the severity of any leakage from them on a three-point scale (none, a little, a lot). These data were used to determine differences in leakage performance. Numbers of laundry items and pads used were recorded to estimate costs, and skin health changes were recorded by the participant or by the researchers (Trial 2b). At the end of testing, participants were interviewed and ranked their preferences (with and without costs), stated the acceptability of each design (highly acceptableâtotally unacceptable) and recorded their overall opinion on a visual analogue scale (VAS) of 0â100 points (worst designâbest design). This VAS score was used with product costs to estimate cost-effectiveness. In addition, a timed pad changing exercise was conducted with 10 women from Trial 2b to determine any differences between product designs.Results: Results presented are for statistically and clinically significant findings.<br/
Bias spectroscopy and simultaneous SET charge state detection of Si:P double dots
We report a detailed study of low-temperature (mK) transport properties of a
silicon double-dot system fabricated by phosphorous ion implantation. The
device under study consists of two phosphorous nanoscale islands doped to above
the metal-insulator transition, separated from each other and the source and
drain reservoirs by nominally undoped (intrinsic) silicon tunnel barriers.
Metallic control gates, together with an Al-AlOx single-electron transistor,
were positioned on the substrate surface, capacitively coupled to the buried
dots. The individual double-dot charge states were probed using source-drain
bias spectroscopy combined with non-invasive SET charge sensing. The system was
measured in linear (VSD = 0) and non-linear (VSD 0) regimes allowing
calculations of the relevant capacitances. Simultaneous detection using both
SET sensing and source-drain current measurements was demonstrated, providing a
valuable combination for the analysis of the system. Evolution of the triple
points with applied bias was observed using both charge and current sensing.
Coulomb diamonds, showing the interplay between the Coulomb charging effects of
the two dots, were measured using simultaneous detection and compared with
numerical simulations.Comment: 7 pages, 6 figure
Establishment of norms in specific areas of the visual field for critical fusion frequency as determined by a modified stroboscope
Establishment of norms in specific areas of the visual field for critical fusion frequency as determined by a modified stroboscop
Controlled single electron transfer between Si:P dots
We demonstrate electrical control of Si:P double dots in which the potential
is defined by nanoscale phosphorus doped regions. Each dot contains
approximately 600 phosphorus atoms and has a diameter close to 30 nm. On
application of a differential bias across the dots, electron transfer is
observed, using single electron transistors in both dc- and rf-mode as charge
detectors. With the possibility to scale the dots down to few and even single
atoms these results open the way to a new class of precision-doped quantum dots
in silicon.Comment: 3 figures, 3 page
Validity of Criteria for Dementia in Older People With Intellectual Disability
Objective: Valid definitions of dementia should discriminate dementia from other forms of cognitive impairment such as intellectual disability (ID). We aimed to evaluate the usefulness of criteria for dementia and mild cognitive impairment (MCI) in ID, including predictive validity, and inter-rater reliability. / Method: We assessed 222 participants in a survey of older adults with ID without Down syndrome at two time points for dementia (T1 and T2). Mean follow-up period was 2.9 years. Dementia diagnoses were made according to International Classification of Diseases, Tenth Revision, Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition), Diagnostic criteria for psychiatric disorders for use with adults with learning disabilities (DC-LD) criteria. At follow-up (T2), raters were blind to initial diagnosis. Predictive validity was determined by comparing odds ratios (ORs) of death, or of having a âpoor outcomeâ (i.e., either dying or being diagnosed with dementia at T2). / Results: All dementia criteria showed substantial inter-rater reliability (Îș > 0.68) and high specificity (âŒ95%). Dementia cases at T1 were more likely to have died at T2 than those with no dementia (33.3% versus 14.9%; OR: 2.85; 95% confidence interval (95% CI): 1.12â7.22) and to have a âpoor outcomeâ (77.8% versus 27.6%; OR: 9.18; 95% CI: 3.43â24.53). At least two dementia cases at T1 were false positives. Those with âMCIâ at T1 were similar to âno dementiaâ cases in terms of poor outcomes at T2. / Conclusion: Dementia diagnostic criteria show substantial reliability and satisfactory validity in ID. The diagnoses were, however, less stable than in the general population and some caution is advisable in those with more severe ID or additional sensory disability. MCI definitions require further consideration in the ID population
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