Entity

Time filter

Source Type

United States

Guo J.,Inner Mongolia University of Technology | Chen J.,Zhengzhou University | Pan E.,The University of Akron
Composite Structures | Year: 2016

Modified couple-stress theory has found many applications in fields related to nanocomposites. However, most investigations so far are based on the corresponding thin-plate or beam theories where the modified couple-stress theory was introduced. In this paper, we present analytical three-dimensional solutions of anisotropic multilayered composite plates with consideration of the modified couple-stress theory. We first expand the solutions in terms of the two-dimensional Fourier series in the horizontal plane to reduce the governing equations to a system of ordinary differential equations, from which we drive analytically the general solution in each layer. We then introduce the propagator matrix method to propagate the solutions from one layer to the next. Numerical examples are carried for homogeneous thick-plates and sandwich plates to show the effect of the non-local parameters on the displacements and stresses induced by the surface load. These results can serve as benchmarks to various thick plate theories in the modeling of layered composite structures with couple-stress effect. © 2016 Elsevier Ltd. Source


Grandfield K.,University of California at San Francisco | Herber R.-P.,University of California at San Francisco | Chen L.,University of California at San Francisco | Djomehri S.,University of California at San Francisco | And 10 more authors.
Bone Reports | Year: 2015

Objective: The objective of this study was to investigate the effect of mechanical strain by mapping physicochemical properties at periodontal ligament (PDL)-bone and PDL-cementum attachment sites and within the tissues per se. Design: Accentuated mechanical strain was induced by applying a unidirectional force of 0.06. N for 14. days on molars in a rat model. The associated changes in functional space between the tooth and bone, mineral forming and resorbing events at the PDL-bone and PDL-cementum attachment sites were identified by using micro-X-ray computed tomography (micro-XCT), atomic force microscopy (AFM), dynamic histomorphometry, Raman microspectroscopy, and AFM-based nanoindentation technique. Results from these analytical techniques were correlated with histochemical strains specific to low and high molecular weight GAGs, including biglycan, and osteoclast distribution through tartrate resistant acid phosphatase (TRAP) staining. Results: Unique chemical and mechanical qualities including heterogeneous bony fingers with hygroscopic Sharpey's fibers contributing to a higher organic (amide III - 1240cm-1) to inorganic (phosphate - 960cm-1) ratio, with lower average elastic modulus of 8GPa versus 12GPa in unadapted regions were identified. Furthermore, an increased presence of elemental Zn in cement lines and mineralizing fronts of PDL-bone was observed. Adapted regions containing bony fingers exhibited woven bone-like architecture and these regions rich in biglycan (BGN) and bone sialoprotein (BSP) also contained high-molecular weight polysaccharides predominantly at the site of polarized bone growth. Conclusions: From a fundamental science perspective the shift in local properties due to strain amplification at the soft-hard tissue attachment sites is governed by semiautonomous cellular events at the PDL-bone and PDL-cementum sites. Over time, these strain-mediated events can alter the physicochemical properties of tissues per se, and consequently the overall biomechanics of the bone-PDL-tooth complex. From a clinical perspective, the shifts in magnitude and duration of forces on the periodontal ligament can prompt a shift in physiologic mineral apposition in cementum and alveolar bone albeit of an adapted quality owing to the rapid mechanical translation of the tooth. © 2015 The Authors. Source


News Article
Site: http://phys.org/chemistry-news/

Researchers at The University of Akron have discovered that a thin layer of water (blue molecules ) between two charged surfaces composed of surfactants (green molecules) --becomes ice-like, lessening the friction between the two surfaces. Credit: The University of Akron New research by scientists at The University of Akron (UA) shows that a nanometer-thin layer of water between two charged surfaces exhibits ice-like tendencies that allow it to withstand pressures of hundreds of atmospheres. The discovery could lead to better ways to minimize friction in a variety of settings. Why water between two surfaces does not always simply squeeze out when placed under severe pressure had never been fully understood. The UA researchers discovered that naturally-occurring charges between two surfaces under intense pressure traps the water, and gives it ice-like qualities. It is this ice-like layer of water—occurring at room temperature—that then lessens the friction between the two surfaces. "For the first time we have a basic understanding of what happens to water under these conditions and why it keeps two surfaces apart," says Professor Ali Dhinojwala. "We had suspected something was happening at the molecular level, and now we have proof." "This discovery could lead to improved designs where low friction surfaces are critically important, such as in biomedical knee implants," says UA graduate student Nishad Dhopatkar. Graduate student Adrian Defante, who was also part of the research team, says "the newfound properties of water might contribute to the development of more effective antimicrobial coatings, as a thin layer of water could prevent bacterial adhesion." Dhinojwala adds that the research conversely offers insight into how water might be kept away from two surfaces, which could lead to better adhesives in watery environments. The study by Dhinojwala and his team can be found in the current issue of Science Advances. More information: N. Dhopatkar et al, Ice-like water supports hydration forces and eases sliding friction, Science Advances (2016). DOI: 10.1126/sciadv.1600763


News Article | August 31, 2016
Site: http://www.cemag.us/rss-feeds/all/rss.xml/all

New research by scientists at The University of Akron (UA) shows that a nanometer-thin layer of water between two charged surfaces exhibits ice-like tendencies that allow it to withstand pressures of hundreds of atmospheres. The discovery could lead to better ways to minimize friction in a variety of settings. Why water between two surfaces does not always simply squeeze out when placed under severe pressure had never been fully understood. The UA researchers discovered that naturally-occurring charges between two surfaces under intense pressure traps the water, and gives it ice-like qualities. It is this ice-like layer of water — occurring at room temperature — that then lessens the friction between the two surfaces. "For the first time we have a basic understanding of what happens to water under these conditions and why it keeps two surfaces apart," says Professor Ali Dhinojwala. "We had suspected something was happening at the molecular level, and now we have proof." "This discovery could lead to improved designs where low friction surfaces are critically important, such as in biomedical knee implants," says UA graduate student Nishad Dhopatkar. Graduate student Adrian Defante, who was also part of the research team, says, "the newfound properties of water might contribute to the development of more effective antimicrobial coatings, as a thin layer of water could prevent bacterial adhesion." Dhinojwala adds that the research conversely offers insight into how water might be kept away from two surfaces, which could lead to better adhesives in watery environments. The study by Dhinojwala and his team can be found in the current issue of Science Advances.


Wu J.,The University of Akron | Soucek M.D.,The University of Akron
Radiation Physics and Chemistry | Year: 2016

The effect of multifunctional monomers or oligomers (MFM/O) additives on electron beam (E-beam) radiation induced crosslinking of poly (styrene-block-isoprene/butadiene-. block-styrene) (SIBS) was studied. Ten types of MFM/O were investigated, including trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), triallyl cyanurate (TAC), polybutadiene diacrylate (PB-diacrylate), ethylene glycol dimethylacrylate (EGDMA), butylene glycol dimethacrylate (BGDMA), 1,2-polybutadiene. The effects of MFM/O concentration and E-beam radiation dose on properties of SIBS were studied including tensile strength, elongation-at-break, modulus, gel content, equilibrium swelling and crosslink density. TMPTA significantly improved the tensile modulus and crosslink density of SIBS. SIBS with TMPTMA and TMTPMA with inhibitor showed a 50% increase in tensile strength. The solubility of MFM/O in SIBS was also investigated by a selective swelling method. The MFM/O were found to be soluble in both phases of SIBS. The viscosity of SIBS with methacrylate type MFM/O was stable at 200. °C. © 2015 Elsevier Ltd. Source

Discover hidden collaborations