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https://www.readbyqxmd.com/read/28548527/liquid-droplets-act-as-compass-needles-for-the-stresses-in-a-deformable-membrane
#1
Rafael D Schulman, René Ledesma-Alonso, Thomas Salez, Elie Raphaël, Kari Dalnoki-Veress
We examine the shape of droplets atop deformable thin elastomeric films prepared with an anisotropic tension. As the droplets generate a deformation in the taut film through capillary forces, they assume a shape that is elongated along the high tension direction. By measuring the contact line profile, the tension in the membrane can be completely determined. Minimal theoretical arguments lead to predictions for the droplet shape and membrane deformation that are in excellent agreement with the data. On the whole, the results demonstrate that droplets can be used as probes to map out the stress field in a membrane...
May 12, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28546891/scaling-law-to-determine-peak-forces-in-tapping-mode-afm-experiments-on-finite-elastic-soft-matter-systems
#2
Horacio V Guzman
Analytical equations to estimate the peak force will facilitate the interpretation and the planning of amplitude-modulation force microscopy (tapping mode) experiments. A closed-form analytical equation to estimate the tip-sample peak forces while imaging soft materials in liquid environment and within an elastic deformation regime has been deduced. We have combined a multivariate regression method with input from the virial-dissipation equations and Tatara's bidimensional deformation contact mechanics model...
2017: Beilstein Journal of Nanotechnology
https://www.readbyqxmd.com/read/28545245/multimodal-bio-inspired-tactile-sensing-module-for-surface-characterization
#3
Thiago Eustaquio Alves de Oliveira, Ana-Maria Cretu, Emil M Petriu
Robots are expected to recognize the properties of objects in order to handle them safely and efficiently in a variety of applications, such as health and elder care, manufacturing, or high-risk environments. This paper explores the issue of surface characterization by monitoring the signals acquired by a novel bio-inspired tactile probe in contact with ridged surfaces. The tactile module comprises a nine Degree of Freedom Microelectromechanical Magnetic, Angular Rate, and Gravity system (9-DOF MEMS MARG) and a deep MEMS pressure sensor embedded in a compliant structure that mimics the function and the organization of mechanoreceptors in human skin as well as the hardness of the human skin...
May 23, 2017: Sensors
https://www.readbyqxmd.com/read/28545047/the-natural-history-of-varicella-zoster-virus-infection-in-norway-further-insights-on-exogenous-boosting-and-progressive-immunity-to-herpes-zoster
#4
Luigi Marangi, Grazina Mirinaviciute, Elmira Flem, Gianpaolo Scalia Tomba, Giorgio Guzzetta, Birgitte Freiesleben de Blasio, Piero Manfredi
We use age-structured models for VZV transmission and reactivation to reconstruct the natural history of VZV in Norway based on available pre-vaccination serological data, contact matrices, and herpes zoster incidence data. Depending on the hypotheses on contact and transmission patterns, the basic reproduction number of varicella in Norway ranges between 3.7 and 5.0, implying a vaccine coverage between 73 and 80% to effectively interrupt transmission with a 100% vaccine efficacy against infection. The varicella force of infection peaks during early childhood (3-5 yrs) and shows a prolonged phase of higher risk during the childbearing period, though quantitative variations can occur depending on contact patterns...
2017: PloS One
https://www.readbyqxmd.com/read/28544950/the-influence-of-continuous-versus-interval-walking-exercise-on-knee-joint-loading-and-pain-in-patients-with-knee-osteoarthritis
#5
Shawn Farrokhi, Prakash Jayabalan, Jonathan A Gustafson, Brian A Klatt, Gwendolyn A Sowa, Sara R Piva
OBJECTIVE: To evaluate whether knee contact force and knee pain are different between continuous and interval walking exercise in patients with knee osteoarthritis (OA). METHODS: Twenty seven patients with unilateral symptomatic knee OA completed two separate walking exercise sessions on a treadmill at 1.3m/s on two different days: 1) a continuous 45min walking exercise session, and 2) three 15min bouts of walking exercise separated by 1h rest periods for a total of 45min of exercise in an interval format...
May 17, 2017: Gait & Posture
https://www.readbyqxmd.com/read/28544447/modulation-of-wetting-gradients-by-tuning-the-interplay-between-surface-structuration-and-anisotropic-molecular-layers-with-bipolar-electrochemistry
#6
Laurent Bouffier, Stéphane Reculusa, Valérie Ravaine, Alexander Kuhn
A new simple and versatile method for the preparation of surface wetting gradients is proposed. It is based on the combination of electrode surface structuration introduced by a sacrificial template approach and the formation of a tuneable molecular gradient by bipolar electrochemistry. The gradient involves the formation of a self-assembled monolayer on gold surface by selecting an appropriate thiol molecule and the subsequent reductive desorption by means of bipolar electrochemistry. Under these conditions, the completion of the reductive desorption process evolves along the bipolar surface with a maximum strength localized at the cathodic edge and a decreasing driving force toward the middle of the surface...
May 22, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28543389/coexistence-of-a-permanent-form-of-a-junctional-reciprocating-tachycardia-and-coronary-sinus-aneurysm-a-case-report
#7
Yuki Shimizu, Osamu Inaba, Masahiko Goya, Kenzo Hirao
A 58-year-old man with a long R-P' narrow QRS tachycardia underwent an electrophysiological study. The tachycardia was diagnosed as permanent form of junctional reciprocating tachycardia (PJRT), and the earliest atrial activation site during tachycardia was coronary sinus (CS) ostium. Radiofrequency ablation at the site was initially not successful because the tip impedance and temperature were unstable. After changing of the ablation catheter to that with contact force sensor, the accessory pathway was immediately ablated and the PJRT was no longer induced...
May 24, 2017: Pacing and Clinical Electrophysiology: PACE
https://www.readbyqxmd.com/read/28543271/characterization-of-cellular-adhesion-reinforcement-by-multiple-bond-force-spectroscopy-in-alveolar-epithelial-cells
#8
Nguyen Ngoc-Minh, Angely Christelle, Andre Dias Sofia, Planus Emmanuelle, Filoche Marcel, Pelle Gabriel, Louis Bruno, Isabey Daniel
BACKGROUND: Integrin-mediated adhesion is a key process by which cells physically connect their environment, express sensitivity and adaptation through mechanotransduction. A critical step of cell adhesion is the formation of the first bonds which individually generate weak contacts (∼tens pN) but can sustain thousand times higher forces (∼tens nN) when associated. RESULTS: We propose an experimental validation by multiple bond force spectroscopy (MFS) of a stochastic model predicting adhesion reinforcement permitted by non cooperative, multiple bonds on which force is homogeneously distributed (called parallel bond configuration)...
May 24, 2017: Biology of the Cell
https://www.readbyqxmd.com/read/28542494/forces-applied-during-classical-touch-assays-for-caenorhabditis-elegans
#9
Adam L Nekimken, Eileen A Mazzochette, Miriam B Goodman, Beth L Pruitt
For decades, Caenorhabditis elegans roundworms have been used to study the sense of touch, and this work has been facilitated by a simple behavioral assay for touch sensation. To perform this classical assay, an experimenter uses an eyebrow hair to gently touch a moving worm and observes whether or not the worm reverses direction. We used two experimental approaches to determine the manner and moment of contact between the eyebrow hair tool and freely moving animals and the forces delivered by the classical assay...
2017: PloS One
https://www.readbyqxmd.com/read/28537607/colloid-oil-water-interface-interactions-in-the-presence-of-multiple-salts-charge-regulation-and-dynamics
#10
J C Everts, S Samin, N A Elbers, J E S van der Hoeven, A van Blaaderen, R van Roij
We theoretically and experimentally investigate colloid-oil-water-interface interactions of charged, sterically stabilized, poly(methyl-methacrylate) colloidal particles dispersed in a low-polar oil (dielectric constant ε = 5-10) that is in contact with an adjacent water phase. In this model system, the colloidal particles cannot penetrate the oil-water interface due to repulsive van der Waals forces with the interface whereas the multiple salts that are dissolved in the oil are free to partition into the water phase...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28537220/patterned-cortical-tension-mediated-by-n-cadherin-controls-cell-geometric-order-in-the-drosophila-eye
#11
Eunice HoYee Chan, Pruthvi Chavadimane Shivakumar, Raphaël Clément, Edith Laugier, Pierre-François Lenne
Adhesion molecules hold cells together but also couple cell membranes to a contractile actomyosin network, which limits the expansion of cell contacts. Despite their fundamental role in tissue morphogenesis and tissue homeostasis, how adhesion molecules control cell shapes and cell patterns in tissues remains unclear. Here we address this question in vivo using the Drosophila eye. We show that cone cell shapes depend little on adhesion bonds and mostly on contractile forces. However, N-cadherin has an indirect control on cell shape...
May 24, 2017: ELife
https://www.readbyqxmd.com/read/28536199/active-depinning-of-bacterial-droplets-the-collective-surfing-of-bacillus-subtilis
#12
Marc Hennes, Julien Tailleur, Gaëlle Charron, Adrian Daerr
How systems are endowed with migration capacity is a fascinating question with implications ranging from the design of novel active systems to the control of microbial populations. Bacteria, which can be found in a variety of environments, have developed among the richest set of locomotion mechanisms both at the microscopic and collective levels. Here, we uncover, experimentally, a mode of collective bacterial motility in humid environment through the depinning of bacterial droplets. Although capillary forces are notoriously enormous at the bacterial scale, even capable of pinning water droplets of millimetric size on inclined surfaces, we show that bacteria are able to harness a variety of mechanisms to unpin contact lines, hence inducing a collective slipping of the colony across the surface...
May 23, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28534787/effect-of-waveform-on-tactile-perception-by-electrovibration-displayed-on-touch-screens
#13
Yasemin Vardar, Burak Guclu, Cagatay Basdogan
In this study, we investigated the effect of input voltage waveform on our haptic perception of electrovibration on touch screens. Through psychophysical experiments performed with eight subjects, we first measured the detection thresholds of electrovibration stimuli generated by sinusoidal and square voltages at various fundamental frequencies. We observed that the subjects were more sensitive to stimuli generated by square wave voltage than sinusoidal one for frequencies lower than 60 Hz. Using Matlab simulations, we showed that the sensation difference of waveforms in low fundamental frequencies occurred due to the frequency-dependent electrical properties of human skin and human tactile sensitivity...
May 16, 2017: IEEE Transactions on Haptics
https://www.readbyqxmd.com/read/28534393/simple-approach-to-high-performance-stretchable-heaters-based-on-kirigami-patterning-of-conductive-paper-for-wearable-thermotherapy-applications
#14
Nam-Su Jang, Kang-Hyun Kim, Sung-Hun Ha, Soo-Ho Jung, Hye Moon Lee, Jong-Man Kim
Recent efforts to develop stretchable resistive heaters open up the possibility for their use in wearable thermotherapy applications. Such heaters should have high electrothermal performance and stability to be used practically, and the fabrication must be simple, economic, reproducible, and scalable. Here we present a simple yet highly efficient way of producing high-performance stretchable heaters, which is based on a facile kirigami pattering (the art of cutting and folding paper) of a highly conductive paper for practical wearable thermotherapy...
May 23, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28532932/intereye-comparison-of-femtosecond-laser-assisted-cataract-surgery-capsulotomy-and-manual-capsulorhexis-edge%C3%A2-strength
#15
Thomas Chan, Ushasree Pattamatta, Mark Butlin, Kerrie Meades, Chandra Bala
PURPOSE: To compare the breaking force required to tear the explanted capsule after femtosecond laser-assisted cataract surgery in the worse eye and manual cataract surgery in the contralateral eye. SETTING: Personaleyes, Sydney, Australia. DESIGN: Prospective nonrandomized case study. METHOD: Patients with bilateral cataract had femtosecond laser-assisted cataract surgery with the Lensx laser in the eye with worse vision and manual cataract surgery in the contralateral eye...
April 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28532424/an-objective-assessment-of-the-variability-in-number-of-drops-per-bottle-of-glaucoma-medication
#16
Daniel B Moore, Judy Beck, Richard J Kryscio
BACKGROUND: The purpose of this study is to evaluate the number of eyedrops available per bottle of a variety of commonly prescribed glaucoma medications. METHODS: Six bottles of each glaucoma medication were tested: three each in the vertical and horizontal orientations. Bottles were housed in a customized force gauge apparatus designed to mimic ballpoint fingertip contact with a bottle. At a standard rate, all drops were expressed from each bottle and counted with an automated drop counter...
May 22, 2017: BMC Ophthalmology
https://www.readbyqxmd.com/read/28529279/comparing-the-occlusal-contact-area-of-individual-teeth-during-low-level-clenching
#17
Hideta Nishimori, Takashi Iida, Hirona Kamiyama, Yoshihiro Komoda, Ryoko Obara, Takashi Uchida, Misao Kawara, Osamu Komiyama
The aim of this study was to investigate the occlusal contact area (OCA) in individual teeth during low-level tooth clenching in 24 healthy participants. Before measurements were made, the 100% maximum voluntary contraction (MVC) was determined. At baseline, all subjects were instructed to close their mouth and touch the opposing teeth with minimal force. Occlusal contact was recorded during three jaw motor tasks (baseline, 20% MVC, and 40% MVC) using a blue silicone material. OCA thickness was determined from images and defined on five levels: level 1 (0-149 µm), level 2 (0-89 µm), level 3 (0-49 µm), level 4 (0-29 µm), and level 5 (0-4 µm)...
May 19, 2017: Journal of Oral Science
https://www.readbyqxmd.com/read/28527431/osmotic-and-diffusio-osmotic-flow-generation-at-high-solute-concentration-ii-molecular-dynamics-simulations
#18
Hiroaki Yoshida, Sophie Marbach, Lydéric Bocquet
In this paper, we explore osmotic transport by means of molecular dynamics (MD) simulations. We first consider osmosis through a membrane and investigate the reflection coefficient of an imperfectly semi-permeable membrane, in the dilute and high concentration regimes. We then explore the diffusio-osmotic flow of a solute-solvent fluid adjacent to a solid surface, driven by a chemical potential gradient parallel to the surface. We propose a novel non-equilibrium MD (NEMD) methodology to simulate diffusio-osmosis, by imposing an external force on every particle, which properly mimics the chemical potential gradient on the solute in spite of the periodic boundary conditions...
May 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28526627/dynamic-fatigue-measurement-of-human-erythrocytes-using-dielectrophoresis
#19
Yuhao Qiang, Jia Liu, E Du
Erythrocytes must undergo severe deformation to pass through narrow capillaries and submicronic splenic slits for several hundred thousand times in their normal lifespan. Studies of erythrocyte biomechanics have been mainly focused on cell deformability and rheology measured from a single application of stress and mostly under a static or quasi-static state using classical biomechanical techniques, such as optical tweezers and micropipette aspiration. Dynamic behavior of erythrocytes in response to cyclic stresses that contributes to the membrane failure in blood circulation is not fully understood...
May 16, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28525820/sensing-inhomogeneous-mechanical-properties-of-human-corneal-descemet-s-membrane-with-afm-nano-indentation
#20
Rosa Di Mundo, Giuseppina Recchia, Mohit Parekh, Alessandro Ruzza, Stefano Ferrari, Giuseppe Carbone
The paper describes a highly space-resolved characterization of the surface mechanical properties of the posterior human corneal layer (Descemet's membrane). This has been accomplished with Atomic Force Microscopy (AFM) nano-indentation by using a probe with a sharp tip geometry. Results indicate that the contact with this biological tissue in liquid occurs with no (or very low) adhesion. More importantly, under the same operating conditions, a broad distribution of penetration depth can be measured on different x-y positions of the tissue surface, indicating a high inhomogeneity of surface stiffness, not yet clearly reported in the literature...
May 10, 2017: Journal of the Mechanical Behavior of Biomedical Materials
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