1,921 research outputs found
Design and Development of a SNAP-8 Mercury Pump Motor Assembly
Design and performance of mercury pump motor for SNAP 8 electrical generato
Photon Diffusion in Microscale Solids
This paper presents a theoretical and experimental investigation of photon
diffusion in highly absorbing microscale graphite. An Nd:YAG continuous wave
(CW) laser is used to heat the graphite samples with thicknesses of 40 microns
and 100 microns. Optical intensities of 10 kW/cm^2 and 20 kW/cm^2 are used in
laser heating. The graphite samples are heated to temperatures of thousands of
kelvins within milliseconds, which are recorded by a 2-color, high-speed
pyrometer. To compare the observed temperatures, the differential equation of
heat conduction is solved across the samples with proper initial and boundary
conditions. In addition to lattice vibrations, photon diffusion is incorporated
into the analytical model of thermal conductivity for solving the heat
equation. The numerical simulations showed close matching between experiment
and theory only when including the photon diffusion equations and existing
material properties data found in the previously published works with no
fitting constants. The results indicate that the commonly-overlooked mechanism
of photon diffusion dominates the heat transfer of many microscale structures
near their evaporation temperatures. In addition, the treatment explains the
discrepancies between thermal conductivity measurements and theory that were
previously described in the scientific literature.Comment: 8 pages, 7 figures, (N.B. there is a typo and minor correction in
Table 1 and References in the online version of the journal, corrected and
highlighted in this PDF
Design of a pulse power supply unit for micro-ECM
Electrochemical micro-machining (μECM) requires a particular pulse power supply unit (PSU) to be developed in order to achieve desired machining performance. This paper summarises the development of a pulse PSU meeting the requirements of μECM. The pulse power supply provides tens of nanosecond pulse duration, positive and negative bias voltages and a polarity switching functionality. It fulfils the needs for tool preparation with reversed pulsed ECM on the machine. Moreover, the PSU is equipped with an ultrafast overcurrent protection which prevents the tool electrode from being damaged in case of short circuits. The developed pulse PSU was used to fabricate micro-tools out of 170 μm WC-Co alloy shafts via micro-electrochemical turning and drill deep holes via μECM in a disk made of 18NiCr6. The electrolyte used for both processes was a mixture of sulphuric acid and NaNO3 aqueous solutions.The research reported in this paper is supported by the European Commission within the project “Minimizing Defects in Micro-Manufacturing Applications (MIDEMMA)” (FP7-2011-NMP-ICT-FoF-285614
Reduced neonatal regulatory T cell response to microbial stimuli associates with subsequent eczema in high risk infants
Background: Regulatory T cells (Treg) play an essential role in early immune programming and shaping the immune response towards a pro‐allergic or tolerant state. We evaluated cord blood Treg and cytokine responses to microbial and non‐microbial stimuli in infants at high risk of allergic disease and their associations with development of allergic disease in the first year.
Methods: Cord blood mononuclear cells from 72 neonates were cultured with toll‐like receptors (TLR2) ligands: lipoteichoic acid (LTA) and heat‐killed Lactobacillus rhamnosus GG (HKL); TLR4 ligand: lipopolysaccharide (LPS); ovalbumin (OVA); anti‐CD3; or media for 48 h. Treg numbers and Treg cytokines were assessed in relation to allergic disease outcomes during the first year of life (eczema and atopic sensitization).
Results: Infants with eczema (n = 24) had reduced percentages of FoxP3hiCD25hi Treg in LTA (p = 0.01, adj p = 0.005) and HKL (p = 0.04, adj p = 0.02) stimulated cultures as well as reduced IL‐10 (p = 0.01) production following HKL stimulation compared to those without eczema (n = 48). No differences in Treg or cytokine responses to LPS, OVA or anti‐CD3 were seen. Infants who developed sensitization had lower percentages of Treg following TLR2 stimulation (but not other stimuli) compared to non‐sensitized infants.
Conclusions: High‐risk children who develop allergic disease in the first year of life have deficient Treg responses to microbial stimuli but not allergen from the time of birth, which may contribute to failure of immune tolerance development in infancy
The views of older women towards mammographic screening: a qualitative and quantitative study
Purpose: Mammographic screening has improved breast cancer survival in the screened age group. This improved survival has not been seen in older women (>70 years) where screening uptake is low. This study explores the views, knowledge and attitudes of older women towards screening.
Methods: Women (>70) were interviewed about breast screening. Interview findings informed the development of a questionnaire which was sent to 1000 women (>70) to quantify their views regarding screening.
Results: Twenty-six women were interviewed and a questionnaire designed. The questionnaire response rate was 48.3% (479/992). Over half (52.9%, 241/456) of respondents were unaware they could request mammography by voluntary self-referral and were unaware of how to arrange this. Most (81.5% 383/470) had not attended breast screening since turning 70. Most (75.6%, 343/454) felt screening was beneficial and would attend if invited. Most, (90.1%, 412/457) felt screening should be offered to all women regardless of age or health.
Conclusions: There is a lack of knowledge about screening in older women. The majority felt that invitation to screening should be extended to the older age group regardless of age or health. The current under-utilised system of voluntary self referral is not supported by older women
Topological Quantum Phase Transition in Synthetic Non-Abelian Gauge Potential
The method of synthetic gauge potentials opens up a new avenue for our
understanding and discovering novel quantum states of matter. We investigate
the topological quantum phase transition of Fermi gases trapped in a honeycomb
lattice in the presence of a synthetic non- Abelian gauge potential. We develop
a systematic fermionic effective field theory to describe a topological quantum
phase transition tuned by the non-Abelian gauge potential and ex- plore its
various important experimental consequences. Numerical calculations on lattice
scales are performed to compare with the results achieved by the fermionic
effective field theory. Several possible experimental detection methods of
topological quantum phase tran- sition are proposed. In contrast to condensed
matter experiments where only gauge invariant quantities can be measured, both
gauge invariant and non-gauge invariant quantities can be measured by
experimentally generating various non-Abelian gauges corresponding to the same
set of Wilson loops
- …