5,515 research outputs found
Optimal group testing designs for estimating prevalence with uncertain testing errors
We construct optimal designs for group testing experiments where the goal is
to estimate the prevalence of a trait by using a test with uncertain
sensitivity and specificity. Using optimal design theory for approximate
designs, we show that the most efficient design for simultaneously estimating
the prevalence, sensitivity and specificity requires three different group
sizes with equal frequencies. However, if estimating prevalence as accurately
as possible is the only focus, the optimal strategy is to have three group
sizes with unequal frequencies. On the basis of a chlamydia study in the
U.S.A., we compare performances of competing designs and provide insights into
how the unknown sensitivity and specificity of the test affect the performance
of the prevalence estimator. We demonstrate that the locally D- and Ds-optimal
designs proposed have high efficiencies even when the prespecified values of
the parameters are moderately misspecified
An examination of janitor services sourcing factors in secondary schools in Hong Kong
Includes bibliographical references (p. 144-150).Thesis (B.Sc)--University of Hong Kong, 2009.published_or_final_versio
Measurement of Adhesion Energy of Electrospun Polymer Membranes Using a Shaft-loaded Blister Test
This study aims to examine the adhesion work of electrospun polymer nano- and micro-fibers. The adhesion energy at the interface of electrospun membrane and a rigid substrate is characterized by a shaft-loaded blister test (SLBT). By controlling the processing parameters, polyvinylidene fluoride (PVDF) fibrous membranes are prepared with fiber diameters ranging from 201 ± 86 nm to 2,724 ± 587 nm. The adhesion energy between electrospun membrane and rigid substrate increases from 8.1 ± 0.7 mJ/m2 to 258.8 ± 43.5 mJ/m2 by use of smaller fiber diameters. Adhesion energies between electrospun PVDF membranes and SiC substrates made of different grain sizes are evaluated. Fibrous membrane produces an adhesion energy as high as 420.1 ± 62.9 mJ/m2 in contact with SiC substrate with a 68 μm grit size. The SLBT methodology is extended to understand the adhesion energy between electrospun membranes. The increase in adhesion work is attributed to an increased area between fiber delaminated surfaces and surface asperities
Antralization at the edge of proximal gastric ulcers: Does Helicobacter pylori infection play a role?
Aim: To determine the prevalence of antralization at the edge of proximal gastric ulcers, and the effect of H. pylori eradication on the mucosal appearances. Methods: Biopsies were taken from the antrum, body and the ulcer edge of patients with benign proximal gastric ulcers before and one year after treatment. Gastric mucosa was classified as antral, transitional or body type. H. pylori positive patients received either triple therapy, or omeprazole. Results: Patients with index ulcers in the incisura, body or fundus (n=116) were analyzed. Antral-type mucosa was more prevalent at the ulcer edge in H. pylori-positive patients than H. pylori-negative patients (93 % vs 60 %, OR=8.95, 95 %CI: 2.47-32.4, P=0.001). At one year, there was a significant reduction in the prevalence of antralization (from 93 % to 61 %, P=0.004) at the ulcer edge in patients with H. pylori being eradicated. However, there was no difference in the prevalence of antralization at the ulcer edge in those with persistent infection. Conclusion: H. pylori infection is associated with antralization at the edge of proximal gastric ulcers, which may be reversible in some patients after eradication of the infection.published_or_final_versio
A Prediction of the B*_c mass in full lattice QCD
By using the Highly Improved Staggered Quark formalism to handle charm,
strange and light valence quarks in full lattice QCD, and NRQCD to handle
bottom valence quarks we are able to determine accurately ratios of the B meson
vector-pseudoscalar mass splittings, in particular,
(m(B*_c)-m(B_c))/(m(B*_s)-m(B_s)). We find this ratio to be 1.15(15), showing
the `light' quark mass dependence of this splitting to be very small. Hence we
predict m(B_c*) = 6.330(7)(2)(6) GeV where the first two errors are from the
lattice calculation and the third from existing experiment. This is the most
accurate prediction of a gold-plated hadron mass from lattice QCD to date.Comment: 4 pages, 2 figure
Bioactive glass composite for orthodontic adhesives - Formation and characterisation of apatites using MAS-NMR and SEM.
OBJECTIVES: To study the dissolution and fluoroapatite (FAP) formation of a new bioactive glass (BAG)-resin adhesive in an acidic solution in reference to neutral solutions, using the magic angle spinning-nuclear magnetic resonance (MAS-NMR) and the scanning electron microscopy (SEM). METHODS: BAG composite disks (n = 90) were prepared from, novel fluoride-containing BAG-resin. Three sample groups (n = 30) of the disks were immersed in Tris buffer pH = 7.3 (TB), neutral artificial saliva pH = 7 (AS7) and acidic artificial saliva pH = 4 (AS4) at ten time points (from 6 h to 6 months). Half of the immersed disks at each time point were crushed into a powder and investigated by the solid state MAS-NMR. SEM studies were undertaken by embedding the other half of the immersed disk in a self-cure acrylic where the fracture surface was imaged. RESULTS: MAS-NMR results show that the BAG composite degraded significantly faster in AS4 compared to TB and AS7. At the end of the immersion period (6 months), around 80% of the glass particles in AS4 had reacted to form an apatite, evidenced by the sharp peak at 2.82 ppm in 31P signals compared to a broader peak in TB and AS7. It also shows evidence of fluorapatite (FAP) formation, indicated by 19F signal at -103 ppm, while signal around -108 ppm indicated the formation of calcium fluoride, from the excess Ca2+ and F- especially on longer immersion. SEM images confirm higher degradation rate of the BAG composite in AS4 and reveal the impact of time on the dissolution of more glass particles. The images also indicate apatite formation around the glass particles in TB and AS4, while it forms predominantly over the disk surface in AS7. SIGNIFICANCE: BAG composite demonstrate smart reactivity in response to pH change which has a potential clinical benefit against demineralization and promoting remineralisation to form more stable fluorapatites
Unveiling the coverage patterns of newspapers on the personal data protection act
collected, used, processed and even transferred to third party organizations. To protect the privacy
of data owners and the security of these data, the Malaysian government has enforced the Personal
Data Protection Act (PDPA) in 2013. Several studies found that Malaysians have low awareness of
the PDPA. Prior literature also shows that the framing of news stories by the media has significant
influence on public awareness and perception toward a covered topic. In this paper, we investigated
how the Malaysian newspapers frame the PDPA news. We extracted a total of 793 news articles
between January 1st 2010 and July 31st 2015 from ten local English newspapers. The results show
that newspapers in general have not given the PDPA enough attention considering its potential
impact on data privacy and security. Nonetheless, newspapers do publish significantly higher
number of PDPA articles after the enforcement period compared to before the enforcement period.
The newspapers also mostly position the PDPA news in the Technology section. The results also
show that more PDPA news originated from foreign sources compared to local sources or the
government. Our findings provide insights into the coverage patterns of local newspapers and the
insufficient level of prominence given to the PDPA. The findings have implications for both the
government and the newspapers as a media
Precise B, B_s and B_c meson spectroscopy from full lattice QCD
We give the first accurate results for and meson masses from
lattice QCD including the effect of , and sea quarks, and we improve
an earlier value for the meson mass. By using the Highly Improved
Staggered Quark action for , and quarks and NRQCD for the
quarks, we are able to achieve an accuracy in the masses of around 10 MeV. Our
results are: = 5.291(18) GeV, = 5.363(11) GeV and =
6.280(10) GeV. Note that all QCD parameters here are tuned from other
calculations, so these are parameter free tests of QCD against experiment. We
also give scalar, , and axial vector, , meson masses. We find
these to be slightly below threshold for decay to and respectively.Comment: 22 pages, 19 figure
Intensive voice treatment for Cantonese-speaking patients with Parkinson's disease effects on intonation and lexical tone production
Also available in print.Thesis (B.Sc.)--University of Hong Kong, 2003."A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, April 30, 2003."published_or_final_versionSpeech and Hearing SciencesBachelorBachelor of Science in Speech and Hearing Science
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