- Layer-specific hyperelastic and viscoelastic characterization of human descending thoracic aortas. [Journal Article]
- JMJ Mech Behav Biomed Mater 2019 Jul 15; 99:27-46
- A layer-specific hyperelastic and viscoelastic characterization of human descending thoracic aortas was experimentally performed. Healthy aortas from twelve beating heart donors with an average age o…
A layer-specific hyperelastic and viscoelastic characterization of human descending thoracic aortas was experimentally performed. Healthy aortas from twelve beating heart donors with an average age of 49.4 years, were received from Transplant Québec. Axial and circumferential strips were prepared from the specimens. They were dissected into intima, media and adventitia layers. Measurements of the opening angles were used to identify the circumferential residual stresses. Uniaxial tensile tests on axial and circumferential strips, together with the Gasser-Ogden-Holzapfel material model, were used to characterize the hyperelastic behaviour of the three aortic layers for each donor. Uniaxial harmonic excitations at different frequency, superimposed to initial stretch values, were used to characterize the viscoelastic behaviour. The storage modulus and the loss tangent were obtained for each layer in both directions; comparison to intact aortic wall was also performed. The generalized Maxwell model, within the framework of nonlinear viscoelasticity with internal variables, was used to obtain the constitutive material parameters. Results showed a positive correlation (p < 0.05 for circumferential media and adventitia) between stiffness and donor age for the three layers of the aorta in both axial and circumferential directions. A significant increase (around 50%) of the storage modulus (i.e. dynamic stiffness) was observed between the quasi-static value and loading at 1 Hz frequency, while further increase in frequency marginally affected its value. The loss tangent was only slightly influenced by the stretch value, which justified the use of the viscoelastic model adopted. Finally, similar loss tangent values were found for the three aortic layers.
- Development of a rapid-viability PCR method for detection of Clostridioides difficile spores from environmental samples. [Journal Article]
- AAnaerobe 2019 Jul 19; :102077
- Clostridioides difficile is a common pathogen that is well known to survive for extended periods of time on environmental healthcare surfaces from fecal contamination. During epidemiological investig…
Clostridioides difficile is a common pathogen that is well known to survive for extended periods of time on environmental healthcare surfaces from fecal contamination. During epidemiological investigations of healthcare-associated infections, it is important to be able to detect whether or not there are viable spores of C. difficile on surfaces. Current methods to detect C. difficile can take up to 7 days for culture and in the case of detection by PCR, viability of the spores cannot be ascertained. Prevention of C. difficile infection in healthcare settings includes adequate cleaning and disinfection of environmental surfaces which increases the likelihood of detecting dead organisms from an environmental sample during an investigation. In this study, we were able to adapt a rapid-viability PCR (RV-PCR) method, first developed for detection of viable Bacillus anthracis spores, for the detection of viable C. difficile spores. RV-PCR uses the change in cycle threshold after incubation to confirm the presence of live organisms. Using this modified method we were able to detect viable C. difficile after 22 h of anaerobic incubation in Cycloserine Cefoxitin Fructose Broth (CCFB). This method also used bead beating combined with the Maxwell 16 Casework kit for DNA extraction and purification and a real-time duplex PCR assay for toxin B and cdd3 genes to confirm the identity of the C. difficile spores. Spiked environmental sponge-wipes with and without added organic load were tested to determine the limit of detection (LOD). The LOD from spiked environmental sponge-wipe samples was 104 spores/mL but after incubation initial spore levels of 101 spores/mL were detected. Use of this method would greatly decrease the amount of time required to detect viable C. difficile spores; incubation of samples is only required for germination (22 h or less) instead of colony formation, which can take up to 7 days. In addition, PCR can then quickly confirm or deny the identity of the organism at the same time it would confirm viability. The presence of viable C. difficile spores could be detected at very low levels within 28 h total compared to the 2 to 10-day process that would be needed for culture, identification and toxin detection.
- Class-C semiconductor lasers with time-delayed optical feedback. [Journal Article]
- PTPhilos Trans A Math Phys Eng Sci 2019 Sep 09; 377(2153):20180124
- We perform a linear stability analysis and numerical bifurcation diagrams of a class-C laser with time-delayed optical feedback. We employ a rate equation system based on the Maxwell-Bloch equations,…
We perform a linear stability analysis and numerical bifurcation diagrams of a class-C laser with time-delayed optical feedback. We employ a rate equation system based on the Maxwell-Bloch equations, and study the influence of the dephasing time on the laser dynamics. We find a stabilizing effect of an intermediate dephasing time, i.e. when moving from a class-B to a class-C laser. At long dephasing times, a destabilization of the laser solution occurs by a feedback-induced unlocking of Rabi oscillations at the second laser threshold. We predict an optimum resistance to time-delayed optical feedback for dephasing times close to the photon cavity lifetime. This article is part of the theme issue 'Nonlinear dynamics of delay systems'.
- Discrimination between healthy and degenerated bovine articular cartilage with a fiber Bragg grating based microindenter. [Journal Article]
- JMJ Mech Behav Biomed Mater 2019 Jul 09; 99:11-17
- CONCLUSIONS: The fiber Bragg grating microindentation system showed the capability to differentiate intact and proteoglycan depleted cartilage with high significance.
- Sex-Based Mhrt Methylation Chromatinizes MeCP2 in the Heart. [Journal Article]
- IiScience 2019 Jun 27; 17:288-301
- In the heart, primary microRNA-208b (pri-miR-208b) and Myheart (Mhrt) are long non-coding RNAs (lncRNAs) encoded by the cardiac myosin heavy chain genes. Although preclinical studies have shown that …
In the heart, primary microRNA-208b (pri-miR-208b) and Myheart (Mhrt) are long non-coding RNAs (lncRNAs) encoded by the cardiac myosin heavy chain genes. Although preclinical studies have shown that lncRNAs regulate gene expression and are protective for pathological hypertrophy, the mechanism underlying sex-based differences remains poorly understood. In this study, we examined DNA- and RNA-methylation-dependent regulation of pri-miR-208b and Mhrt. Expression of pri-miR-208b is elevated in the left ventricle of the female heart. Despite indistinguishable DNA methylation between sexes, the interaction of MeCP2 on chromatin is subject to RNase digestion, highlighting that affinity of the methyl-CG reader is broader than previously thought. A specialized procedure to isolate RNA from soluble cardiac chromatin emphasizes sex-based affinity of an MeCP2 co-repressor complex with Rest and Hdac2. Sex-specific Mhrt methylation chromatinizes MeCP2 at the pri-miR-208b promoter and extends the functional relevance of default transcriptional suppression in the heart.
- Obstacle effects on electrocommunication with applications to object detection of underwater robots. [Journal Article]
- BBBioinspir Biomim 2019 Jul 18
- Some fish species communicate electrically (termed electrocommunication) in turbid waters where other communication modalities fail. Inspired by this biological phenomenon, we have developed an artif…
Some fish species communicate electrically (termed electrocommunication) in turbid waters where other communication modalities fail. Inspired by this biological phenomenon, we have developed an artificial electrocommunication system for underwater robots . Due to the complex terrain of the ocean, electrocommunication could be affected by potential obstacles. In this paper, we investigate the obstacle effects on electrocommunication in a quasi-two-dimensional water environment. We first employ Fresnel zone theory to theoretically analyze the obstacle effects on electrocommunication. We then simplify the ocean terrain into 32 types of obstacles according to their material, relative location, geometry, and size, and use ANSYS Maxwell to simulate the effect of these obstacles on electrocommunication. We fabricate the same types of obstacles as in the simulation, and further conduct electrocommunication experiments with these obstacles in a swimming pool. Both the simulations and experiments show that the material, relative location, geometry, and size of the obstacles all affect the electrocommunication to varying degrees. Finally, we demonstrate that it is possible to identify and detect underwater objects based on the obtained obstacle effects, indicating that electrocommunication could be a new viable method for underwater object detection.
- JC Virus and APOL1 Risk Alleles in Black South Africans With Hypertension-Attributed CKD. [Journal Article]
- KIKidney Int Rep 2019; 4(7):939-945
- CONCLUSIONS: There was a strong association between the absence of JC viruria and CKD. Studies with a larger sample are essential to determine the renoprotective effects of JCV and its interactions with APOL1.
- Correction to: Promoting Recruitment using Information Management Efficiently (PRIME): study protocol for a steppedwedge cluster randomised controlled trial within the REstart or STop Antithrombotics Randomised Trial (RESTART). [Journal Article]
- TTrials 2019 07 17; 20(1):438
- In the original publication  figures S1 and S2 should have been part of the main text rather than additional files.
In the original publication  figures S1 and S2 should have been part of the main text rather than additional files.
- Heterogeneity in age at death for adults with developmental disability. [Journal Article]
- JIJ Intellect Disabil Res 2019 Jul 16
- CONCLUSIONS: Research on age at death for adults with developmental disability must account for heterogeneity among disability types in order to ensure reliable estimates. Failure to do so conceals important differences between disability types, which can misguide public health and preventive care efforts to reduce premature mortality and/or provide aging-related supports.
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- Framework analysis: A worked example from a midwifery research. [Journal Article]
- ECEnferm Clin 2019 Jul 13
- CONCLUSIONS: The details of each stage of the analysis were explained to guide researchers through essential steps in undertaking framework analysis. Health care researchers may find a worked example addressed in this paper as useful when analyzing qualitative data.