A Mechanism Behind the Mechanotransduction of Surface Characteristics in Osteoblasts

Biomaterials for use in bone regeneration and healing range from metal and metal alloy implants to hydrogel-based solutions. These materials can be optimized to increase bone healing and integration by improving the mechanical and biological properties. Regardless of the material itself, the cell-substrate interaction is key to the success of the biomaterial once implanted. Substrate surface characteristics such as roughness, wettability, and particle density are well-known contributors to a substrate’s overall osteogenic potential, and therefore the substrate\u27s overall success. Unfortunately, it is still unknown how these substrate surface characteristics are transduced into intracellular signals by cells, preventing specific tailoring of biomaterial characteristics to maximize osteogenesis. One theory that has been postulated is that substrate characteristics modulate cytoskeletal changes which in turn differentially regulate numerous cell pathways. Specifically, the canonical Wnt signaling pathway relies on β-catenin translocation to the nucleus to regulate transcription factors, which in the case of osteoblastic cells, regulate pro-osteogenic genes. Another role of β-catenin is its contribution to the formation and stabilization of cell adhesions such as focal adhesions and cadherins. Furthermore, previous studies have suggested that the β-catenin pool that stabilizes adhesions and cadherins may also be the same β-catenin pool that functions to induce osteogenesis. Evaluating the link between substrate surface characteristics, focal adhesions, and β-catenin could reveal how cells transduce substrate surface characteristics into intracellular signals and enable greater optimization of biomaterials for bone regeneration

Association of the Sweet-Liking Phenotype and Craving for Alcohol With the Response to Naltrexone Treatment in Alcohol Dependence: A Randomized Clinical Trial

Identification of moderators of the response to naltrexone hydrochloride treatment for alcohol dependence could improve clinical care for patients with alcohol use disorders. To investigate the preliminary finding that the sweet-liking (SL) phenotype interacts with a high level of craving for alcohol and is associated with an improved response to naltrexone in alcohol dependence. This 12-week double-blind, randomized, placebo-controlled clinical trial was conducted from February 1, 2010, to April 30, 2012, in an academic outpatient medical center. Eighty actively drinking patients were randomized by the SL (n = 22) or the sweet-disliking (SDL) (n = 58) phenotype and by pretreatment high (n = 40) or low (n = 40) craving for alcohol, with high craving defined as greater than the median. Patients and staff were blinded to categorization. Patients were excluded for unstable medical or psychiatric illness, including dependence on drugs other than nicotine. Four patients (2 in the placebo arm and 2 in the naltrexone arm) stopped medication therapy because of adverse effects. Data were analyzed from January 15, 2013, to May 15, 2016, based on intention to treat. Oral naltrexone hydrochloride, 50 mg/d, or daily placebo with weekly to biweekly brief counseling. The a priori hypothesis tested SL/SDL phenotype, pretreatment craving, and their interaction as moderators of frequency of abstinent and heavy drinking days during treatment, assessed with the timeline follow-back method. Eighty patients were randomized (57 men [71%]; 23 women [29%]; mean [SD] age, 47.0 [8.6] years). A nonsignificant effect of naltrexone on heavy drinking was noted (4.8 fewer heavy drinking days; Cohen d = 0.45; 95% CI, -0.01 to 0.90; F1,67 = 3.52; P = .07). The SL phenotype moderated the effect of naltrexone on heavy drinking (6.1 fewer heavy drinking days; Cohen d = 0.58; 95% CI, 0.12-1.03; F1,67 = 5.65; P = .02) and abstinence (10.0 more abstinent days; Cohen d = 0.57; 95% CI, 0.11-1.02; F1,67 = 5.36; P = .02), and high craving moderated heavy drinking (7.1 fewer heavy drinking days; Cohen d = 0.66; 95% CI, 0.20-1.11; F1,67 = 7.37; P = .008). The combination of the SL phenotype and high craving was associated with a strong response to naltrexone, with 17.1 fewer heavy drinking days (Cohen d = 1.07; 95% CI, 0.58-1.54; F1,67 = 19.33; P < .001) and 28.8 more abstinent days (Cohen d = 0.72; 95% CI, 0.25-1.17; F1,67 = 8.73; P = .004) compared with placebo. The SL phenotype and a high craving for alcohol independently and particularly in combination are associated with a positive response to naltrexone. The SL/SDL phenotype and a high craving for alcohol merit further investigation as factors to identify patients with alcohol dependence who are responsive to naltrexone. clinicaltrials.gov Identifier: NCT01296646

Dynamic stereo microscopy for studying particle sedimentation

We demonstrate a new method for measuring the sedimentation of a single colloidal bead by using a combination of optical tweezers and a stereo microscope based on a spatial light modulator. We use optical tweezers to raise a micron-sized silica bead to a fixed height and then release it to observe its 3D motion while it sediments under gravity. This experimental procedure provides two independent measurements of bead diameter and a measure of Faxén’s correction, where the motion changes due to presence of the boundary

Local Structure and Bonding of Carbon Nanothreads Probed by High-Resolution Transmission Electron Microscopy

Carbon nanothreads are a new one-dimensional sp^3-bonded nanomaterial of CH stoichiometry synthesized from benzene at high pressure and room temperature by slow solid-state polymerization. The resulting threads assume crystalline packing hundreds of micrometers across. We show high-resolution electron microscopy (HREM) images of hexagonal arrays of well-aligned thread columns that traverse the 80–100 nm thickness of the prepared sample. Diffuse scattering in electron diffraction reveals that nanothreads are packed with axial and/or azimuthal disregistry between them. Layer lines in diffraction from annealed nanothreads provide the first evidence of translational order along their length, indicating that this solid-state reaction proceeds with some regularity. HREM also reveals bends and defects in nanothread crystals that can contribute to the broadening of their diffraction spots, and electron energy-loss spectroscopy confirms them to be primarily sp^3-hybridized, with less than 27% sp^2 carbon, most likely associated with partially saturated “degree-4” threads

Organic-Silica Interactions in Saline:Elucidating the Structural Influence of Calcium in Low-Salinity Enhanced Oil Recovery

Abstract Enhanced oil recovery using low-salinity solutions to sweep sandstone reservoirs is a widely-practiced strategy. The mechanisms governing this remain unresolved. Here, we elucidate the role of Ca2+ by combining chemical force microscopy (CFM) and molecular dynamics (MD) simulations. We probe the influence of electrolyte composition and concentration on the adsorption of a representative molecule, positively-charged alkylammonium, at the aqueous electrolyte/silica interface, for four electrolytes: NaCl, KCl, MgCl2, and CaCl2. CFM reveals stronger adhesion on silica in CaCl2 compared with the other electrolytes, and shows a concentration-dependent adhesion not observed for the other electrolytes. Using MD simulations, we model the electrolytes at a negatively-charged amorphous silica substrate and predict the adsorption of methylammonium. Our simulations reveal four classes of surface adsorption site, where the prevalence of these sites depends only on CaCl2 concentration. The sites relevant to strong adhesion feature the O− silica site and Ca2+ in the presence of associated Cl−, which gain prevalence at higher CaCl2 concentration. Our simulations also predict the adhesion force profile to be distinct for CaCl2 compared with the other electrolytes. Together, these analyses explain our experimental data. Our findings indicate in general how silica wettability may be manipulated by electrolyte concentration

A Numerical Model of an Acoustic Metamaterial Using the Boundary Element Method Including Viscous and Thermal Losses

[EN] In recent years, boundary element method (BEM) and finite element method (FEM) implementations of acoustics in fluids with viscous and thermal losses have been developed. They are based on the linearized Navier¿Stokes equations with no flow. In this paper, such models with acoustic losses are applied to an acoustic metamaterial. Metamaterials are structures formed by smaller, usually periodic, units showing remarkable physical properties when observed as a whole. Acoustic losses are relevant in metamaterials in the millimeter scale. In addition, their geometry is intricate and challenging for numerical implementation. The results are compared with existing measurements.The authors wish to thank Mads J. Herring Jensen, from the company COMSOL, for his support in setting up the FEM model of the metamaterial. J. Sanchez-Dehesa acknowledges the support by the Spanish Ministerio de Economia y Competitividad, and the European Union Fondo Europeo de Desarrollo Regional (FEDER) through Project No. TEC2014-53088-C3-1-R.Cutanda-Henriquez, V.; Andersen, PR.; Jensen, JS.; Juhl, PM.; Sánchez-Dehesa Moreno-Cid, J. (2017). A Numerical Model of an Acoustic Metamaterial Using the Boundary Element Method Including Viscous and Thermal Losses. Journal of Computational Acoustics. 25(4):1750006-1-1750006-11. doi:10.1142/S0218396X17500060S1750006-11750006-11254Craster, R. V., & Guenneau, S. (Eds.). (2013). Acoustic Metamaterials. Springer Series in Materials Science. doi:10.1007/978-94-007-4813-2Cummer, S. A., Christensen, J., & Alù, A. (2016). Controlling sound with acoustic metamaterials. Nature Reviews Materials, 1(3). doi:10.1038/natrevmats.2016.1Cutanda-Henríquez, V., & Juhl, P. M. (2013). An axisymmetric boundary element formulation of sound wave propagation in fluids including viscous and thermal losses. The Journal of the Acoustical Society of America, 134(5), 3409-3418. doi:10.1121/1.4823840Bruneau, M., Herzog, P., Kergomard, J., & Polack, J. D. (1989). General formulation of the dispersion equation in bounded visco-thermal fluid, and application to some simple geometries. Wave Motion, 11(5), 441-451. doi:10.1016/0165-2125(89)90018-8Kampinga, W. R., Wijnant, Y. H., & de Boer, A. (2010). Performance of Several Viscothermal Acoustic Finite Elements. Acta Acustica united with Acustica, 96(1), 115-124. doi:10.3813/aaa.918262Kampinga, W. R., Wijnant, Y. H., & de Boer, A. (2011). An Efficient Finite Element Model for Viscothermal Acoustics. Acta Acustica united with Acustica, 97(4), 618-631. doi:10.3813/aaa.918442BELTMAN, W. M. (1999). VISCOTHERMAL WAVE PROPAGATION INCLUDING ACOUSTO-ELASTIC INTERACTION, PART I: THEORY. Journal of Sound and Vibration, 227(3), 555-586. doi:10.1006/jsvi.1999.2355Graciá-Salgado, R., García-Chocano, V. M., Torrent, D., & Sánchez-Dehesa, J. (2013). Negative mass density andρ-near-zero quasi-two-dimensional metamaterials: Design and applications. Physical Review B, 88(22). doi:10.1103/physrevb.88.224305Homentcovschi, D., & Miles, R. N. (2011). An analytical-numerical method for determining the mechanical response of a condenser microphone. The Journal of the Acoustical Society of America, 130(6), 3698-3705. doi:10.1121/1.3652853Geuzaine, C., & Remacle, J.-F. (2009). Gmsh: A 3-D finite element mesh generator with built-in pre- and post-processing facilities. International Journal for Numerical Methods in Engineering, 79(11), 1309-1331. doi:10.1002/nme.257