2,297 research outputs found
Evaluation of laser fluorescence in monitoring non-cavitated caries lesion progression on smooth surfaces in vitro.
The aim of this study was to evaluate the performance of a pen-type laser fluorescence (LF) device (LFpen: DIAGNOdent pen) to detect and monitor the progression of caries-like lesions on smooth surfaces. Fifty-two bovine enamel blocks were submitted to three different demineralisation cycles for caries-like lesion induction using Streptococcus mutans, Lactobacillus casei and Actinomyces naeslundii. At baseline and after each cycle, the enamel blocks were analysed under Knoop surface micro-hardness (SMH) and an LFpen. One enamel block after each cycle was randomly chosen for Raman spectroscopy analysis. Cross-sectional micro-hardness (CSMH) was performed at different depths (20, 40, 60, 80 and 100 μm) in 26 enamel blocks after the second cycle and 26 enamel blocks after the third cycle. Average values of SMH (± standard deviation (SD)) were 319.3 (± 21.5), 80.5 (± 31.9), 39.8 (± 12.7), and 29.77 (± 10.34) at baseline and after the first, second and third cycles, respectively. Statistical significant difference was found among all periods (p  0.05). One sample of each cycle was characterised through Raman spectroscopy analysis. It can be concluded that LF was effective in detecting the first demineralisation on enamel; however, the method did not show any effect in monitoring lesion progression after three cycles of in vitro demineralisation
Spectroscopic perspective on the interplay between electronic and magnetic properties of magnetically doped topological insulators
We combine low energy muon spin rotation (LE-SR) and soft-X-ray
angle-resolved photoemission spectroscopy (SX-ARPES) to study the magnetic and
electronic properties of magnetically doped topological insulators,
(Bi,Sb)Te. We find that one achieves a full magnetic volume fraction in
samples of (V/Cr)(Bi,Sb)Te at doping levels x 0.16.
The observed magnetic transition is not sharp in temperature indicating a
gradual magnetic ordering. We find that the evolution of magnetic ordering is
consistent with formation of ferromagnetic islands which increase in number
and/or volume with decreasing temperature. Resonant ARPES at the V edge
reveals a nondispersing impurity band close to the Fermi level as well as V
weight integrated into the host band structure. Calculations within the
coherent potential approximation of the V contribution to the spectral function
confirm that this impurity band is caused by V in substitutional sites. The
implications of our results on the observation of the quantum anomalous Hall
effect at mK temperatures are discussed
Quantitative properties of complex porous materials calculated from X-ray μCT images
A microcomputed tomography (μCT) facility and computational infrastructure developed at the Department of Applied
Mathematics at the Australian National University is described. The current experimental facility is capable of acquiring
3D images made up of 20003 voxels on porous specimens up to 60 mm diameter with resolutions down to 2 μm. This
allows the three-dimensional (3D) pore-space of porous specimens to be imaged over several orders of magnitude. The
computational infrastructure includes the establishment of optimised and distributed memory parallel algorithms for image
reconstruction, novel phase identification, 3D visualisation, structural characterisation and prediction of mechanical and
transport properties directly from digitised tomographic images.
To date over 300 porous specimens exhibiting a wide variety of microstructure have been imaged and analysed. In this
paper, analysis of a small set of porous rock specimens with structure ranging from unconsolidated sands to complex carbonates
are illustrated. Computations made directly on the digitised tomographic images have been compared to laboratory
measurements. The results are in excellent agreement. Additionally, local flow, diffusive and mechanical properties can
be numerically derived from solutions of the relevant physical equations on the complex geometries; an experimentally
intractable problem. Structural analysis of data sets includes grain and pore partitioning of the images. Local granular
partitioning yields over 70,000 grains from a single image. Conventional grain size, shape and connectivity parameters
are derived. The 3D organisation of grains can help in correlating grain size, shape and orientation to resultant physical
properties. Pore network models generated from 3D images yield over 100000 pores and 200000 throats; comparing the
pore structure for the different specimens illustrates the varied topology and geometry observed in porous rocks. This
development foreshadows a new numerical laboratory approach to the study of complex porous materials
3D imaging and flow characterization of the pore space of carbonate core samples
Carbonate rocks are inherently heterogeneous having been laid down in a range of depositional environments and having undergone significant diagenesis. They are particularly difficult to characterise as the pore sizes can vary over orders of magnitudes and connectivity of pores of different scales can impact greatly on flow properties. For example, separate vuggy porosity in an underlying matrix pore system can increase the porosity, but not the permeability and lead to large residual oil saturations due to trapping in vugs. A touching vug network can have a dramatic effect on permeability and lead to higher recoveries. In this paper we image a range of carbonate core material; from model carbonate cores to core material from outcrops and reservoirs via 3D via micro-CT. Image-based calculations of porosity, MICP and permeability on 3D images of the carbonate systems are directly compared to experimental data from the same or sister core material and give good agreement. The carbonate systems studied include samples with well connected macroporous systems and other where the macroporosity is poorly
connected. Simulation of permeability on these systems and direct analysis of local flow properties within the system allows one to directly illustrate the important role of the connectivity of macropores on flow properties. Pore network models generated from the
images illustrate the varied topology obtained in different carbonate samples and show a dramatic difference when compared to clastic samples. Many carbonate samples can include a significant proportion of microporosity (pores of 2 microns or less in extent) which are not directly accessible via current micro-CT capabilities. We discuss how one can map the structure and the topology of microporous regions crucial in studies of flow, production and recovery in carbonates. A hybrid numerical scheme is developed to measure the contribution of microporosity to the overall core permeability. Overall these results show the important role of identifying the connectivity of the pore sizes in dictating the single phase flow properties. Implications to two phase relative permeability and recovery are briefly discussed
SynthRAD2023 Grand Challenge dataset: generating synthetic CT for radiotherapy
Purpose: Medical imaging has become increasingly important in diagnosing and
treating oncological patients, particularly in radiotherapy. Recent advances in
synthetic computed tomography (sCT) generation have increased interest in
public challenges to provide data and evaluation metrics for comparing
different approaches openly. This paper describes a dataset of brain and pelvis
computed tomography (CT) images with rigidly registered CBCT and MRI images to
facilitate the development and evaluation of sCT generation for radiotherapy
planning.
Acquisition and validation methods: The dataset consists of CT, CBCT, and MRI
of 540 brains and 540 pelvic radiotherapy patients from three Dutch university
medical centers. Subjects' ages ranged from 3 to 93 years, with a mean age of
60. Various scanner models and acquisition settings were used across patients
from the three data-providing centers. Details are available in CSV files
provided with the datasets.
Data format and usage notes: The data is available on Zenodo
(https://doi.org/10.5281/zenodo.7260705) under the SynthRAD2023 collection. The
images for each subject are available in nifti format.
Potential applications: This dataset will enable the evaluation and
development of image synthesis algorithms for radiotherapy purposes on a
realistic multi-center dataset with varying acquisition protocols. Synthetic CT
generation has numerous applications in radiation therapy, including diagnosis,
treatment planning, treatment monitoring, and surgical planning.Comment: 15 pages, 4 figures, 9 tables, pre-print submitted to Medical Physics
- dataset. The training dataset is available on Zenodo at
https://doi.org/10.5281/zenodo.7260705 from April, 1st 202
Responsive Asthma Care for Teens (ReACT): Development protocol for an adaptive mobile health intervention for adolescents with asthma
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.Introduction Asthma is a leading cause of youth morbidity in the USA, affecting >8% of youth. Adherence to inhaled corticosteroids (ICS) can prevent asthma-related morbidity; however, the typical adolescent with asthma takes fewer than 50% of their prescribed doses. Adolescents are uniquely vulnerable to suboptimal asthma self-management due to still-developing executive functioning capabilities that may impede consistent self-regulation and weaken attempts to use problem solving to overcome barriers to ICS adherence.
Methods and analysis The aims of this project are to improve adherence to ICS as an important step towards better self-management among adolescents aged 13–17 years diagnosed with asthma by merging the efficacious behaviour change strategies found in behavioural health interventions with scalable, adaptive mobile health (mHealth) technologies to create the Responsive Asthma Care for Teens programme (ReACT). ReACT intervention content will be developed through an iterative user-centred design process that includes conducting (1) one-on-one interviews with 20 teens with asthma; (2) crowdsourced feedback from a nationally representative panel of 100 adolescents with asthma and (3) an advisory board of youth with asthma, a paediatric pulmonologist and a behavioural health expert. In tandem, we will work with an existing technology vendor to programme ReACT algorithms to allow for tailored intervention delivery. We will conduct usability testing of an alpha version of ReACT with a sample of 20 target users to assess acceptability and usability of our mHealth intervention. Participants will complete a 4-week run-in period to monitor their adherence with all ReACT features turned off. Subsequently, participants will complete a 4-week intervention period with all ReACT features activated. The study started in October 2018 and is scheduled to conclude in late 2019.
Ethics and dissemination Institutional review board approval was obtained at the University of Kansas and the University of Florida. We will submit study findings for presentation at national research conferences that are well attended by a mix of psychologists, allied health professionals and physicians. We will publish study findings in peer-reviewed journals read by members of the psychology, nursing and pulmonary communities
Ecological stability of Late Pleistocene-to-Holocene Lesotho, southern Africa, facilitated human upland habitation
Investigation of Homo sapiens’ palaeogeographic expansion into African mountain environments are changing the understanding of our species’ adaptions to various extreme Pleistocene climates and habitats. Here, we present a vegetation and precipitation record from the Ha Makotoko rockshelter in western Lesotho, which extends from ~60,000 to 1,000 years ago. Stable carbon isotope ratios from plant wax biomarkers indicate a constant C3-dominated ecosystem up to about 5,000 years ago, followed by C4 grassland expansion due to increasing Holocene temperatures. Hydrogen isotope ratios indicate a drier, yet stable, Pleistocene and Early Holocene compared to a relatively wet Late Holocene. Although relatively cool and dry, the Pleistocene was ecologically reliable due to generally uniform precipitation amounts, which incentivized persistent habitation because of dependable freshwater reserves that supported rich terrestrial foods and provided prime locations for catching fish
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