764 research outputs found
A study of the effect of closing the one room schools of Kansas
Call number: LD2668 .T4 1943 N4Master of Scienc
Periodic solutions of fully nonlinear autonomous equations of Benjamin-Ono type
We prove the existence of time-periodic, small amplitude solutions of
autonomous quasilinear or fully nonlinear completely resonant pseudo-PDEs of
Benjamin-Ono type in Sobolev class. The result holds for frequencies in a
Cantor set that has asymptotically full measure as the amplitude goes to zero.
At the first order of amplitude, the solutions are the superposition of an
arbitrarily large number of waves that travel with different velocities
(multimodal solutions). The equation can be considered as a Hamiltonian,
reversible system plus a non-Hamiltonian (but still reversible) perturbation
that contains derivatives of the highest order. The main difficulties of the
problem are: an infinite-dimensional bifurcation equation, and small divisors
in the linearized operator, where also the highest order derivatives have
nonconstant coefficients. The main technical step of the proof is the reduction
of the linearized operator to constant coefficients up to a regularizing rest,
by means of changes of variables and conjugation with simple linear
pseudo-differential operators, in the spirit of the method of Iooss, Plotnikov
and Toland for standing water waves (ARMA 2005). Other ingredients are a
suitable Nash-Moser iteration in Sobolev spaces, and Lyapunov-Schmidt
decomposition.
(Version 2: small change in Section 2).Comment: 47 page
Cigar Smoking Among U.S. Students: Reported Use After Adding Brands to Survey Items
Background: Among U.S. youth overall, cigars are the most commonly used tobacco product after cigarettes. However, youth who identify their products by brand names, not general terms like “cigar,” may underreport use. Purpose: To examine changes in reported cigar (cigar, cigarillo, or little cigar) smoking among students following inclusion of cigar brand examples on the National Youth Tobacco Survey (NYTS). Methods: Data from the 2011 and 2012 NYTS and National Survey on Drug Use and Health (NSDUH) were analyzed in 2013 to estimate ever and current cigar smoking, overall and by race/ ethnicity. The 2012 NYTS included cigar brand examples (Black and Mild, Swisher Sweets, Dutch Masters, White Owl, Phillies Blunt) in the survey instructions and ever use question, but the 2011 NYTS and 2011 and 2012 NSDUH did not. Results: NYTS ever cigar smoking was higher in 2012 (27.8%) than 2011 (19.5%) among black students overall. Current cigar smoking was 60%–70% higher among black females and students agedZ17 years, in 2012 than 2011. For black females, current cigar smoking (11.5%) was two times greater than that of white females (4.3%) in 2012, whereas the prevalence among these subgroups was comparable in 2011. Similar changes were not observed among these subgroups in the 2011– 2012 NSDUH. Conclusions: This study highlights the high burden of cigar use among U.S. youth and suggests that NYTS ascertainment of cigar smoking may have improved by including brands. Disparities in cigar smoking need to be addressed to prevent and reduce all youth tobacco use. (Am J Prev Med 2014;47(2S1):S28–S35) Published by Elsevier Inc. on behalf of American Journal of Preventive Medicin
A New Thermal Elasto-Hydrodynamic Lubrication Solver Implementation in OpenFOAM
Designing effective thermal management systems within transmission systems requires simulations to consider the contributions from phenomena such as hydrodynamic lubrication regions. Computational fluid dynamics (CFD) remains computationally expensive for practical cases of hydrodynamic lubrication while the thermo elasto-hydrodynamic lubrication (TEHL) theory has demonstrated good accuracy at a lower computational cost. To account for the effects of hydro-dynamic lubrication in high-power transmission systems requires integrating TEHL into a CFD framework such that these methodologies can be interfaced. This study takes an initial step by developing a TEHL solver within OpenFOAM such that the program is prepared to be interfaced with a CFD module in future versions. The OpenFOAM solver includes the Elrod-Adams cavitation model, thermal effects, and elastic deformation of the surfaces, and considers mixing between the recirculating flow and oil feed by applying energy and mass continuity. A sensitivity study of the film mesh is presented to show the solution variation with refinement along the circumferential, axial and radial directions. A validation case is presented of an experimental single axial groove journal bearing which shows good agreement in the pressure and temperature results. The peak pressure in the film is predicted within 12% and the peak temperature in the bush is predicted within 5% when comparing the centerline profiles
A machine learning-driven approach to predicting thermo-elasto-hydrodynamic lubrication in journal bearings
Traditional methods of evaluating the performance of journal bearings, for example thermal-elastic-hydrodynamic- lubrication theory, are limited to simplified conditions that often fail to accurately model real-world components. Numerical models that include additional phenomena such as cavitation and fully coupled effects like deformation, temperature, pressure and viscosity can be more accurate but require a large amount of computational overhead, making analysis slower and more costly. To address this limitation, a novel machine learning-driven approach is developed to predict the 2D distribution of surface deformation, film thickness, temperature, and pressure across the bearing surface as a function of design variables such as load and speed. The training dataset, generated using a fully coupled Reynolds’ Equation solver implemented in OpenFOAM, contains a significantly extended range of conditions than in previous studies with approximately 39 000 000 points encompassing 4925 different test cases. Modelled bearing speeds range from 2000 to 10 000 rpm, while load values are varied between 1 and 30 kN. Predicting surface deformation, film thickness, temperature and pressure across the bearing surface results in a mean absolute percentage error below 0.4 % or better. The work also demonstrates that the trained models have a strong ability to generalise the prediction beyond the original training data range with only a 1 % error at up to 200 % of the highest trained speed. This work also demonstrates that machine learning-based processes are a practical alternative to physics-based numerical modelling, especially in cases where rapid performance evaluation is desired as real-time calculation is possible with significantly reduced computational cost. This has the potential to enable development of rapid design optimisation tools and real-time performance monitoring at high resolution and with low latency. Using consumer hardware, it is found that the neural network-based approach is faster than the existing numerical modelling technique by a factor of over 10 000, enabling real-time predictions of lubrication systems
Detection of a reduced susceptibility to chlorfenapyr in the malaria vector Anopheles gambiae contrasts with full susceptibility in Anopheles funestus across Africa
New insecticides have recently been produced to help control pyrethroid-resistant malaria vectors including the pyrrole, chlorfenapyr. Monitoring the susceptibility of mosquito populations against this new product and potential cross-resistance with current insecticides is vital for better resistance management. In this study, we assessed the resistance status of the major malaria vectors Anopheles gambiae and Anopheles funestus to chlorfenapyr across Africa and explored potential cross-resistance with known pyrethroid resistance markers. Efficacy of chlorfenapyr 100 µg/ml against An. gambiae and An. funestus from five Cameroonian locations, the Democratic Republic of Congo, Ghana, Uganda, and Malawi was assessed using CDC bottle assays. Synergist assays were performed with PBO (4%), DEM (8%) and DEF (0.25%) and several pyrethroid-resistant markers were genotyped in both species to assess potential cross-resistance between pyrethroids and chlorfenapyr. Resistance to chlorfenapyr was detected in An. gambiae populations from DRC (Kinshasa) (mortality rate: 64.3 ± 7.1%) Ghana (Obuasi) (65.9 ± 7.4%), Cameroon (Mangoum; 75.2 ± 7.7% and Nkolondom; 86.1 ± 7.4). In contrast, all An. funestus populations were fully susceptible. A negative association was observed between the L1014F-kdr mutation and chlorfenapyr resistance with a greater frequency of homozygote resistant mosquitoes among the dead mosquitoes after exposure compared to alive (OR 0.5; P = 0.02) whereas no association was found between GSTe2 (I114T in An. gambiae; L119F in An. funestus) and resistance to chlorfenapyr. A significant increase of mortality to chlorfenapyr 10 µg/ml was observed in An. funestus after to PBO, DEM and DEF whereas a trend for a decreased mortality was observed in An. gambiae after PBO pre-exposure. This study reveals a greater risk of chlorfenapyr resistance in An. gambiae populations than in An. funestus. However, the higher susceptibility in kdr-resistant mosquitoes points to higher efficacy of chlorfenapyr against the widespread kdr-based pyrethroid resistance
A new twist on PIFE: photoisomerisation-related fluorescence enhancement
PIFE was first used as an acronym for protein-induced fluorescence
enhancement, which refers to the increase in fluorescence observed upon the
interaction of a fluorophore, such as a cyanine, with a protein. This
fluorescence enhancement is due to changes in the rate of cis/trans
photoisomerisation. It is clear now that this mechanism is generally applicable
to interactions with any biomolecule and, in this review, we propose that PIFE
is thereby renamed according to its fundamental working principle as
photoisomerisation-related fluorescence enhancement, keeping the PIFE acronym
intact. We discuss the photochemistry of cyanine fluorophores, the mechanism of
PIFE, its advantages and limitations, and recent approaches to turn PIFE into a
quantitative assay. We provide an overview of its current applications to
different biomolecules and discuss potential future uses, including the study
of protein-protein interactions, protein-ligand interactions and conformational
changes in biomolecules.Comment: No Comment
SaferBirths bundle of care protocol: a stepped-wedge cluster implementation project in 30 public health-facilities in five regions, Tanzania
Background
The burden of stillbirth, neonatal and maternal deaths are unacceptably high in low- and middle-income countries, especially around the time of birth. There are scarce resources and/or support implementation of evidence-based training programs. SaferBirths Bundle of Care is a well-proven package of innovative tools coupled with data-driven on-the-job training aimed at reducing perinatal and maternal deaths. The aim of this project is to determine the effect of scaling up the bundle on improving quality of intrapartum care and perinatal survival.
Methods
The project will follow a stepped-wedge cluster implementation design with well-established infrastructures for data collection, management, and analysis in 30 public health facilities in regions in Tanzania. Healthcare workers from selected health facilities will be trained in basic neonatal resuscitation, essential newborn care and essential maternal care. Foetal heart rate monitors (Moyo), neonatal heart rate monitors (NeoBeat) and skills trainers (NeoNatalie Live) will be introduced in the health facilities to facilitate timely identification of foetal distress during labour and improve neonatal resuscitation, respectively. Heart rate signal-data will be automatically collected by Moyo and NeoBeat, and newborn resuscitation training by NeoNatalie Live.
Given an average of 4000 baby-mother pairs per year per health facility giving an estimate of 240,000 baby-mother pairs for a 2-years duration, 25% reduction in perinatal mortality at a two-sided significance level of 5%, intracluster correlation coefficient (ICC) to be 0.0013, the study power stands at 0.99.
Discussion
Previous reports from small-scale Safer Births Bundle implementation studies show satisfactory uptake of interventions with significant improvements in quality of care and lives saved. Better equipped and trained birth attendants are more confident and skilled in providing care. Additionally, local data-driven feedback has shown to drive continuous quality of care improvement initiatives, which is essential to increase perinatal and maternal survival. Strengths of this research project include integration of innovative tools with existing national guidelines, local data-driven decision-making and training. Limitations include the stepwise cluster implementation design that may lead to contamination of the intervention, and/or inability to address the shortage of healthcare workers and medical supplies beyond the project scope.
Trial registration
Name of Trial Registry: ISRCTN Registry.
Trial registration number: ISRCTN30541755.
Date of Registration: 12/10/2020.
Type of registration: Prospectively Registered.publishedVersio
On the Korteweg-de Vries approximation for uneven bottoms
In this paper we focus on the water waves problem for uneven bottoms on a
two-dimensionnal domain. Starting from the symmetric Boussinesq systems derived
in [Chazel, Influence of topography on long water waves, 2007], we recover the
uncoupled Korteweg-de Vries (KdV) approximation justified by Schneider and
Wayne for flat bottoms, and by Iguchi in the context of bottoms tending to zero
at infinity at a substantial rate. The goal of this paper is to investigate the
validity of this approximation for more general bathymetries. We exhibit two
kinds of topography for which this approximation diverges from the Boussinesq
solutions. A topographically modified KdV approximation is then proposed to
deal with such bathymetries. Finally, all the models involved are numerically
computed and compared
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