386 research outputs found
In-vivo measurement of the human soft tissues constitutive laws. Applications to Computer Aided Surgery
In the 80's, biomechanicians were asked to work on Computer Aided Surgery
applications since orthopaedic surgeons were looking for numerical tools able
to predict risks of fractures. More recently, biomechanicians started to
address soft tissues arguing that most of the human body is made of such
tissues that can move as well as deform during surgical gestures [1]. An
intra-operative use of a continuous Finite Element (FE) Model of a given tissue
mainly faces two problems: (1) the numerical simulations have to be
"interactive", i.e. sufficiently fast to provide results during surgery (which
can be a strong issue in the context of hyperelastic models for example) and
(2) during the intervention, the surgeon needs a device that can be used to
provide to the model an estimation of the patient-specific constitutive
behaviour of the soft tissues. This work proposes an answer to the second
point, with the design of a new aspiration device aiming at characterizing the
in vivo constitutive laws of human soft tissues. The device was defined in
order to permit sterilization as well an easy intra-operative use
Impacts of COVID-19 lockdown on private domestic groundwater sample numbers, E. coli presence and E. coli concentration across Ontario, January 2020âMarch 2021: An interrupted time-series analysis
Approximately 1.5 million individuals in Ontario are supplied by private water wells (private groundwater supplies). Unlike municipal supplies, private well water quality remains unregulated, with owners responsible for testing, treating, and maintaining their own water supplies. The COVID-19 global pandemic and associated non-pharmaceutical interventions (NPIs) have impacted many environmental (e.g., surface water and air quality) and human (e.g., healthcare, transportation) systems over the past 15-months (January 2020 to March 2021). To date, the impact of these interventions on private groundwater systems remains largely unknown. Accordingly, the current study aimed to investigate the impact of a province-wide COVID-19 lockdown (late-March 2020) on health behaviours (i.e., private domestic groundwater sampling) and groundwater quality (via Escherichia coli (E. coli) detection and concentration) in private well water in Ontario, using time-series analyses (seasonal decomposition, interrupted time-series) of a large-spatio-temporal dataset (January 2016 to March 2021; N = 743,200 samples). Findings indicate that lockdown concurred with an immediate (p = 0.015) and sustained (p \u3c 0.001) decrease in sampling rates, equating to approximately 2200 fewer samples received per week post-interruption. Likewise, a slightly decreased E. coli detection rate was observed approximately one month after lockdowns began (p = 0.003), while the proportion of âhighly contaminatedâ samples (i.e., E. coli \u3e 10 CFU/100 mL) was shown to increase within one month (p = 0.02), followed by a sustained decrease for the remainder of the year (May 2020âDecember 2020). Analyses strongly suggest that COVID-19 interventions resulted in discernible impacts on both well user behaviours and hydrogeological mechanisms. Findings may be used as an evidence-base for assisting policy makers, public health practitioners and private well owners in developing recommendations and mitigation strategies to manage public health risks during extreme and/or unprecedented future events
A light sterilizable pipette device for the in vivo estimation of human soft tissues constitutive laws
Abstract-This paper introduces a new light device for the in vivo estimation of human soft tissues constitutive laws. It consists of an aspiration pipette able to meet the very severe sterilization and handling issues imposed during surgery. The simplicity of the device, free of any electronic circuitry, allows using it as an ancillary instrument. The deformation of the aspired tissue is imaged via a mirror using an external camera. The paper describes the experimental setup as well as the protocol that should be used during surgery. First feasibility measurements are shown for human tongue and forearm skin
On the dynamical behavior of the ABC model
We consider the ABC dynamics, with equal density of the three species, on the
discrete ring with sites. In this case, the process is reversible with
respect to a Gibbs measure with a mean field interaction that undergoes a
second order phase transition. We analyze the relaxation time of the dynamics
and show that at high temperature it grows at most as while it grows at
least as at low temperature
Fluorescent oxide nanoparticles adapted to active tips for near-field optics
We present a new kind of fluorescent oxide nanoparticles with properties well
suited to active-tip based near-field optics. These particles with an average
diameter in the range 5-10 nm are produced by Low Energy Cluster Beam
Deposition (LECBD) from a YAG:Ce3+ target. They are studied by transmission
electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), classical
photoluminescence, cathodoluminescence and near-field scanning optical
microscopy (NSOM). Particles of extreme photo-stability as small as 10 nm in
size are observed. These emitters are validated as building blocks of active
NSOM tips by coating a standard optical tip with a 10 nm thick layer of
YAG:Ce3+ particles directly in the LECBD reactor and by subsequently performing
NSOM imaging of test surfaces.Comment: Changes made following Referee's comments; added references; one
added figure. See story on this article at:
http://nanotechweb.org/cws/article/tech/3606
Photoluminescent diamond nanoparticles for cell labeling: study of the uptake mechanism in mammalian cells
Diamond nanoparticles (nanodiamonds) have been recently proposed as new
labels for cellular imaging. For small nanodiamonds (size <40 nm) resonant
laser scattering and Raman scattering cross-sections are too small to allow
single nanoparticle observation. Nanodiamonds can however be rendered
photoluminescent with a perfect photostability at room temperature. Such a
remarkable property allows easier single-particle tracking over long
time-scales. In this work we use photoluminescent nanodiamonds of size <50 nm
for intracellular labeling and investigate the mechanism of their uptake by
living cells . By blocking selectively different uptake processes we show that
nanodiamonds enter cells mainly by endocytosis and converging data indicate
that it is clathrin mediated. We also examine nanodiamonds intracellular
localization in endocytic vesicles using immunofluorescence and transmission
electron microscopy. We find a high degree of colocalization between vesicles
and the biggest nanoparticles or aggregates, while the smallest particles
appear free in the cytosol. Our results pave the way for the use of
photoluminescent nanodiamonds in targeted intracellular labeling or biomolecule
deliver
Nanostructured 3D Constructs Based on Chitosan and Chondroitin Sulphate Multilayers for Cartilage Tissue Engineering
Nanostructured three-dimensional constructs combining layer-by-layer technology (LbL) and template leaching were processed and evaluated as possible support structures for cartilage tissue engineering. Multilayered constructs were formed by depositing the polyelectrolytes chitosan (CHT) and chondroitin sulphate (CS) on either bidimensional glass surfaces or 3D packet of paraffin spheres. 2D CHT/CS multi-layered constructs proved to support the attachment and proliferation of bovine chondrocytes (BCH). The technology was transposed to 3D level and CHT/CS multi-layered hierarchical scaffolds were retrieved after paraffin leaching. The obtained nanostructured 3D constructs had a high porosity and water uptake capacity of about 300%. Dynamical mechanical analysis (DMA) showed the viscoelastic nature of the scaffolds. Cellular tests were performed with the culture of BCH and multipotent bone marrow derived stromal cells (hMSCs) up to 21 days in chondrogenic differentiation media. Together with scanning electronic microscopy analysis, viability tests and DNA quantification, our results clearly showed that cells attached, proliferated and were metabolically active over the entire scaffold. Cartilaginous extracellular matrix (ECM) formation was further assessed and results showed that GAG secretion occurred indicating the maintenance of the chondrogenic phenotype and the chondrogenic differentiation of hMSCs
Capture the fracture: a best practice framework and global campaign to break the fragility fracture cycle
Summary
The International Osteoporosis Foundation (IOF) Capture the Fracture Campaign aims to support implementation of Fracture Liaison Services (FLS) throughout the world.
Introduction
FLS have been shown to close the ubiquitous secondary fracture prevention care gap, ensuring that fragility fracture sufferers receive appropriate assessment and intervention to reduce future fracture risk.
Methods
Capture the Fracture has developed internationally endorsed standards for best practice, will facilitate change at the national level to drive adoption of FLS and increase awareness of the challenges and opportunities presented by secondary fracture prevention to key stakeholders. The Best Practice Framework (BPF) sets an international benchmark for FLS, which defines essential and aspirational elements of service delivery.
Results
The BPF has been reviewed by leading experts from many countries and subject to beta-testing to ensure that it is internationally relevant and fit-for-purpose. The BPF will also serve as a measurement tool for IOF to award âCapture the Fracture Best Practice Recognitionâ to celebrate successful FLS worldwide and drive service development in areas of unmet need. The Capture the Fracture website will provide a suite of resources related to FLS and secondary fracture prevention, which will be updated as new materials become available. A mentoring programme will enable those in the early stages of development of FLS to learn from colleagues elsewhere that have achieved Best Practice Recognition. A grant programme is in development to aid clinical systems which require financial assistance to establish FLS in their localities.
Conclusion
Nearly half a billion people will reach retirement age during the next 20Â years. IOF has developed Capture the Fracture because this is the single most important thing that can be done to directly improve patient care, of both women and men, and reduce the spiralling fracture-related care costs worldwide.</p
Measurements of Elastic Moduli of Silicone Gel Substrates with a Microfluidic Device
Thin layers of gels with mechanical properties mimicking animal tissues are widely used to study the rigidity sensing of adherent animal cells and to measure forces applied by cells to their substrate with traction force microscopy. The gels are usually based on polyacrylamide and their elastic modulus is measured with an atomic force microscope (AFM). Here we present a simple microfluidic device that generates high shear stresses in a laminar flow above a gel-coated substrate and apply the device to gels with elastic moduli in a range from 0.4 to 300 kPa that are all prepared by mixing two components of a transparent commercial silicone Sylgard 184. The elastic modulus is measured by tracking beads on the gel surface under a wide-field fluorescence microscope without any other specialized equipment. The measurements have small and simple to estimate errors and their results are confirmed by conventional tensile tests. A master curve is obtained relating the mixing ratios of the two components of Sylgard 184 with the resulting elastic moduli of the gels. The rigidity of the silicone gels is less susceptible to effects from drying, swelling, and aging than polyacrylamide gels and can be easily coated with fluorescent tracer particles and with molecules promoting cellular adhesion. This work can lead to broader use of silicone gels in the cell biology laboratory and to improved repeatability and accuracy of cell traction force microscopy and rigidity sensing experiments
Ultra-fast responsive colloidal-polymer composite-based volatile organic compounds (VOC) sensor using nanoscale easy tear process
There is an immense need for developing a simple, rapid, and inexpensive detection assay for health-care applications or monitoring environments. To address this need, a photonic crystal (PC)-based sensor has been extensively studied due to its numerous advantages such as colorimetric measurement, high sensitivity, and low cost. However, the response time of a typical PC-based sensor is relatively slow due to the presence of the inevitable upper residual layer in colloidal structures. Hence, we propose an ultra-fast responsive PC-based volatile organic compound (VOC) sensor by using a "nanoscale easy tear (NET) process" inspired by commercially available "easy tear package". A colloidal crystal-polydimethylsiloxane (PDMS) composite can be successfully realized through nanoscale tear propagation along the interface between the outer surface of crystallized nanoparticles and bulk PDMS. The response time for VOC detection exhibits a significant decrease by allowing the direct contact with VOCs, because of perfect removal of the residual on the colloidal crystals. Moreover, vapor-phase VOCs can be monitored, which had been previously impossible. High-throughput production of the patterned colloidal crystal-polymer composite through the NET process can be applied to other multiplexed selective sensing applications or may be used for nanomolding templates
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