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Mechanical engineering

Prerak Gupta, Mimi Adhikary, Joseph Christakiran M, Manishekhar Kumar, Nandana Bhardwaj, Biman B Mandal
Composite biomaterials as artificial bone graft materials are pushing the present frontiers of bioengineering. In this study, a biomimetic, osteoconductive tricomposite scaffold made of hydroxyapatite (HA) embedded in non-mulberry Antheraea assama (A. assama) silk fibroin fibers and its fibroin solution is explored for osteogenic potential. Scaffolds were physico-chemically characterized for morphology, porosity, secondary structure conformation, water retention ability, biodegradability and mechanical property...
October 26, 2016: ACS Applied Materials & Interfaces
N C Carvalho, Y Fan, M E Tobar
In the context of engineered quantum systems, there is a demand for superconducting tunable devices, able to operate with high-quality factors at power levels equivalent to only a few photons. In this work, we developed a 3D microwave re-entrant cavity with such characteristics ready to provide a very fine-tuning of a high-Q resonant mode over a large dynamic range. This system has an electronic tuning mechanism based on a mechanically amplified piezoelectric actuator, which controls the resonator dominant mode frequency by changing the cavity narrow gap by very small displacements...
September 2016: Review of Scientific Instruments
Haiyan Jia, Zhangjun Huang, Zhaofu Fei, Paul J Dyson, Zhen Zheng, Xinling Wang
Hydrogels are polymeric materials which have a relatively high capacity for holding water. Recently, a double network (DN) technique was developed to fabricate hydrogels with a toughness comparable to rubber. The mechanical properties of DN hydrogels may be attributed to the brittle sacrificial bonding network of one hydrogel, facilitating stress dispersion, combined with ductile polymer chains of a second hydrogel. Herein, we report a novel class of tuneable DN hydrogels composed of a polyurethane (PU) hydrogel and a stronger, dipole-dipole and H-bonding interaction reinforced (DHIR) hydrogel...
October 26, 2016: ACS Applied Materials & Interfaces
Yang Yu, Yan Liu, Chen Zong, Qingbo Yu, Xue Yang, Lei Liang, Fei Ye, Li Nong, Yuxian Jia, Yongkui Lu, Zhipeng Han
Mesenchymal stem cells (MSCs) are generally used in regenerative medicine, tissue engineering and therapy for immune disorder diseases. However, due to the immunosuppressive function of MSCs, the application of MSCs in breast cancer therapy remains limited. Sirt1 is the closest mammalian homologue of the yeast enzyme Sir2 which has an established capacity to influence yeast replicative lifespan. In this study, we demonstrated the effect of MSCs with Sirt1 overexpression (MSCs-Sirt1) in mice bearing 4T1 breast cancer and investigated the underlying mechanism...
October 26, 2016: Scientific Reports
Chengwei Wang, Celso Grebogi, Murilo S Baptista
The electric power system is one of the cornerstones of modern society. One of its most serious malfunctions is the blackout, a catastrophic event that may disrupt a substantial portion of the system, playing havoc to human life and causing great economic losses. Thus, understanding the mechanisms leading to blackouts and creating a reliable and resilient power grid has been a major issue, attracting the attention of scientists, engineers, and stakeholders. In this paper, we study the blackout problem in power grids by considering a practical phase-oscillator model...
September 2016: Chaos
Tatiana Ermakova, Benjamin Fabian, Rüdiger Zarnekow
BACKGROUND: Cloud computing promises to essentially improve healthcare delivery performance. However, shifting sensitive medical records to third-party cloud providers could create an adoption hurdle because of security and privacy concerns. OBJECTIVES: This study examines the effect of confidentiality assurance in a cloud-computing environment on individuals' willingness to accept the infrastructure for inter-organizational sharing of medical data. METHODS: We empirically investigate our research question by a survey with over 260 full responses...
October 26, 2016: Applied Clinical Informatics
Sen Zhang, Rana Anjum, Rachel Squillace, Sara Nadworny, Tianjun Zhou, Jeff Keats, Yaoyu Ning, Scott D Wardwell, David Miller, Youngchul Song, Lindsey Eichinger, Lauren Moran, Wei-Sheng Huang, Shuangying Liu, Dong Zou, Yihan Wang, Qurish Mohemmad, Hyun Gyung Jang, Emily Ye, Narayana Narasimhan, Frank Wang, Juan Miret, Xiaotian Zhu, Tim Clackson, David Dalgarno, William C Shakespeare, Victor M Rivera
PURPOSE: Non-small cell lung cancers (NSCLCs) harboring ALK gene rearrangements (ALK(+)) typically become resistant to the first-generation anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor (TKI) crizotinib through development of secondary resistance mutations in ALK or disease progression in the brain. Mutations that confer resistance to second-generation ALK TKIs ceritinib and alectinib have also been identified. Here, we report the structure and first comprehensive preclinical evaluation of the next-generation ALK TKI brigatinib...
October 25, 2016: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
Iara P Calil, Elizabeth P B Fontes
BACKGROUND: Among the environmental limitations that affect plant growth, viruses cause major crop losses worldwide and represent serious threats to food security. Significant advances in the field of plant-virus interactions have led to an expansion of potential strategies for genetically engineered resistance in crops during recent years. Nevertheless, the evolution of viral virulence represents a constant challenge in agriculture that has led to a continuing interest in the molecular mechanisms of plant-virus interactions that affect disease or resistance...
October 24, 2016: Annals of Botany
Yingfei Xue, Vinayak Sant, Julie Phillippi, Shilpa Sant
Valvular heart diseases are the third leading cause of cardiovascular disease, resulting in more than 25,000 deaths annually in the United States. Heart valve tissue engineering (HVTE) has emerged as a putative treatment strategy such that the designed construct would ideally withstand native dynamic mechanical environment, guide regeneration of the diseased tissue and more importantly, have the ability to grow with the patient. These desired functions could be achieved by biomimetic design of tissue-engineered constructs that recapitulate in vivo heart valve microenvironment with biomimetic architecture, optimal mechanical properties and possess suitable biodegradability and biocompatibility...
October 22, 2016: Acta Biomaterialia
Mehrdad Namdari, Ali Eatemadi
Heart valves are currently under thorough investigation in tissue engineering (TE) research. Mechanical and biological heart valve prostheses which are recently used have several shortcomings. While allogenic and xenogenic biological prostheses are related to graft rejection, degeneration and thrombosis, resulting in a high rate of reoperation. Mechanical prostheses on the other hand are based on metallic, carbon, and polymeric components, and require continuous treatment with anticoagulant, which result in adverse reactions, e...
October 22, 2016: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Massimo Alfano, Manuela Nebuloni, Raffaele Allevi, Pietro Zerbi, Erika Longhi, Roberta Lucianò, Irene Locatelli, Angela Pecoraro, Marco Indrieri, Chantal Speziali, Claudio Doglioni, Paolo Milani, Francesco Montorsi, Andrea Salonia
In the fields of biomaterials and tissue engineering simulating the native microenvironment is of utmost importance. As a major component of the microenvironment, the extracellular matrix (ECM) contributes to tissue homeostasis, whereas modifications of native features are associated with pathological conditions. Furthermore, three-dimensional (3D) geometry is an important feature of synthetic scaffolds favoring cell stemness, maintenance and differentiation. We analyzed the 3D structure, geometrical measurements and anisotropy of the ECM isolated from (i) human bladder mucosa (basal lamina and lamina propria) and muscularis propria; and, (ii) bladder carcinoma (BC)...
October 25, 2016: Scientific Reports
J J Brown, N C Moore, O D Supekar, J C Gertsch, V M Bright
The recent development of low-temperature (<200 °C) atomic layer deposition (ALD) for fabrication of freestanding nanostructures has enabled consideration of active device design based on engineered ultrathin films. This paper explores audible sound production from thermoacoustic loudspeakers fabricated from suspended tungsten nanobridges formed by ALD. Additionally, this paper develops an approach to lumped-element modeling for design of thermoacoustic nanodevices and relates the near-field plane wave model of individual transducer beams to the far-field spherical wave sound pressure that can be measured with standard experimental techniques...
November 25, 2016: Nanotechnology
I Stefani, M A Asnaghi, J J Cooper-White, S Mantero
Cardiovascular diseases represent a major global health burden, with high rates of mortality and morbidity. Autologous grafts are commonly used to replace damaged or failing blood vessels, however such approaches are hampered by the scarcity of suitable graft tissue, donor site morbidity and poor long-term stability. Tissue engineering has been investigated as a means by which exogenous vessel grafts can be produced, with varying levels of success to date, a result of mismatched mechanical properties of these vessel substitutes and inadequate ex vivo vessel tissue genesis...
October 24, 2016: Journal of Tissue Engineering and Regenerative Medicine
Inge A E W van Loosdregt, Sylvia Dekker, Patrick W Alford, Cees W J Oomens, Sandra Loerakker, Carlijn V C Bouten
Understanding cell contractility is of fundamental importance for cardiovascular tissue engineering, due to its major impact on the tissue's mechanical properties as well as the development of permanent dimensional changes, e.g., by contraction or dilatation of the tissue. Previous attempts to quantify contractile cellular stresses mostly used strongly aligned monolayers of cells, which might not represent the actual organization in engineered cardiovascular tissues such as heart valves. In the present study, therefore, we investigated whether differences in organization affect the magnitude of intrinsic stress generated by individual myofibroblasts, a frequently used cell source for in vitro engineered heart valves...
October 24, 2016: Cardiovascular Engineering and Technology
Zahra Zarekhalili, S Hajir Bahrami, M Ranjbar-Mohammadi, Peiman Brouki Milan
In this work three dimensional biodegradable nanofiberous scaffolds containing poly(ε-caprolactone) (PCL), poly(vinyl alcohol) (PVA) and gum tragacanth (GT) were successfully fabricated through two nozzles electrospinning process. For this purpose, PVA/GT blend (Blend: B) solution (60:40wt %) was injected from one syringe and poly(ε-caprolactone) solution from the other one. Presence of PVA and PCL in the formulation improved the electrospinning process of GT solution and mechanical properties of the fabricated nanofibers...
October 21, 2016: International Journal of Biological Macromolecules
Kaixuan Ren, Haitao Cui, Qinghua Xu, Chaoliang He, Gao Li, Xuesi Chen
Bone marrow-derived mesenchymal stem cells (BMSCs) possess vast potential for tissue engineering and regenerative medicine. In this study, an injectable hydrogel comprising poly(L-glutamic acid)-graft-tyramine (PLG-g-TA) with tunable microenvironment was developed via enzyme-catalyzed crosslinking, and used as artificial extracellular matrix (ECM) to explore the behaviors of BMSCs during three dimensional (3D) culture. It was found that the mechanical property, porous structure as well as degradation process of the hydrogels could be tuned by changing the copolymer concentration...
October 24, 2016: Biomacromolecules
Antonietta Franco, Richard N Kitsis, Julie A Fleischer, Evripidis Gavathiotis, Opher S Kornfeld, Guohua Gong, Nikolaos Biris, Ann Benz, Nir Qvit, Sara K Donnelly, Yun Chen, Steven Mennerick, Louis Hodgson, Daria Mochly-Rosen, Gerald W Dorn
Mitochondria are dynamic organelles, remodeling and exchanging contents during cyclic fusion and fission. Genetic mutations of mitofusin (Mfn) 2 interrupt mitochondrial fusion and cause the untreatable neurodegenerative condition, Charcot Marie Tooth disease type 2A (CMT2A). It has not been possible to directly modulate mitochondrial fusion, in part because the structural basis of mitofusin function is incompletely understood. Here we show that mitofusins adopt either a fusion-constrained or fusion-permissive molecular conformation directed by specific intramolecular binding interactions, and demonstrate that mitofusin-dependent mitochondrial fusion can be regulated by targeting these conformational transitions...
October 24, 2016: Nature
Shinji Kanegawa, Yoshihito Shiota, Soonchul Kang, Kazuyuki Takahashi, Hajime Okajima, Akira Sakamoto, Tatsuya Iwata, Hideki Kandori, Kazunari Yoshizawa, Osamu Sato
The polarization switching mechanism is used in various devices such as pyroelectric sensors and memory devices. The change in polarization mostly occurs by ion displacement. The development of materials whose polarization switches via electron transfer in order to enhance operation speed is a challenge. We devised a synthetic and crystal engineering strategy that enables the selective synthesis of a [CrCo] heterometallic dinuclear complex with a polar crystal structure, wherein polarization changes stem from intramolecular charge transfer between Co and the ligand...
October 24, 2016: Journal of the American Chemical Society
Xuewu Li, Tian Shi, Cong Liu, Qiaoxin Zhang, Xingjiu Huang
Aluminum alloys are vulnerable to penetrating and peeling failures in seawater and preparing a barrier coating to isolate the substrate from corrosive medium is an effective anticorrosion method. Inspired by the lotus leaves effect, a wetting alloy surface with enhanced anticorrosion behavior has been prepared via etch, deposition, and low-surface-energy modification. Results indicate that excellent superamphiphobicity has been achieved after the modification of the constructed hierarchical labyrinth-like microstructures and dendritic nanostructures...
October 24, 2016: Scientific Reports
C I Fiedler, E A Aisenbrey, J A Wahlquist, C M Heveran, V L Ferguson, S J Bryant, R R McLeod
Current hydrogels used for tissue engineering are limited to a single range of mechanical properties within the replicated tissue construct. We show that repeated in-swelling by a single hydrogel pre-cursor solution into an existing polymerized hydrogel followed by photo-exposure increases hydrogel mechanical properties. The process is demonstrated with a photo-clickable thiol-ene hydrogel using a biocompatible precursor solution of poly(ethylene glycol) dithiol and 8-arm poly(ethylene glycol) functionalized with norbornene...
October 24, 2016: Soft Matter
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