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Mechanical compression

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https://www.readbyqxmd.com/read/28738450/the-effect-of-pressure-on-organic-reactions-in-fluids-a-new-theoretical-perspective
#1
REVIEW
Bo Chen, Roald Hoffmann, Roberto Cammi
This Review brings a new perspective to the study of chemical reactions in compressed fluid media. We begin by reviewing the substantial insight gained from more than 50 years of experimental studies on organic reactions in solution under pressure. These led to a proper estimation of the critical roles of volume of activation (Δ(≠) V) and reaction volume (ΔV) in understanding pressure effect on rates and equilibria of organic reactions. A recently developed computational method, the XP-PCM (extreme pressure polarizable continuum model) method, capable of carrying out quantum mechanical calculations of reaction pathways of molecules under pressure, is introduced...
July 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28738168/role-of-age-and-injury-mechanism-in-cervical-spine-injury-tolerance-under-head-contact-loading
#2
Narayan Yoganandan, Sajal Chirvi, Liming Voo, Frank A Pintar, Anjishnu Banerjee
OBJECTIVE: To determine the influence of age on cervical spine tolerance to injury from head contact loading using survival analysis. METHODS: This study analyzed data from previously conducted experiments using Post Mortem Human Subject specimens (PMHS). Group A tests used the upright intact head-cervical column experimental model. The inferior end of the specimen was fixed, head was balanced by a mechanical system, and natural lordosis was removed. Specimens were placed on a testing device via a load cell...
July 24, 2017: Traffic Injury Prevention
https://www.readbyqxmd.com/read/28738158/efficient-interfacially-driven-vehiculization-of-corticosteroids-by-pulmonary-surfactant
#3
Alberto Hidalgo, Fabrizio Salomone, Nieves Fresno, Guillermo Orellana, Antonio Cruz, Jesus Perez-Gil
Pulmonary surfactant is a crucial system to stabilize the respiratory air-liquid interface. Furthermore, pulmonary surfactant has been proposed as an effective method for targeting drugs to the lungs. However, few studies have examined in detail the mechanisms of incorporation of drugs into surfactant, the impact of the presence of drugs on pulmonary surfactant performance at the interface under physiologically-meaningful conditions, or the ability of pulmonary surfactant to use the air-liquid interface to vehiculise drugs to long distances...
July 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28736922/effect-of-implantoplasty-on-fracture-resistance-and-surface-roughness-of-standard-diameter-dental-implants
#4
Xavier Costa-Berenguer, Marta García-García, Alba Sánchez-Torres, Mariano Sanz-Alonso, Rui Figueiredo, Eduard Valmaseda-Castellón
OBJECTIVE: To assess the effect of implantoplasty on the fracture resistance, surface roughness, and macroscopic morphology of standard diameter (4.1 mm) external connection dental implants. MATERIALS AND METHODS: An in vitro study was conducted in 20 screw-shaped titanium dental implants with an external connection. In 10 implants, the threads and surface were removed and polished with high-speed burs (implantoplasty), while the remaining 10 implants were used as controls...
July 23, 2017: Clinical Oral Implants Research
https://www.readbyqxmd.com/read/28736126/outcomes-following-osteosynthesis-of-periprosthetic-hip-fractures-around-cemented-tapered-polished-stems
#5
S T Goudie, S Patil, J T Patton, J F Keating
We retrospectively reviewed outcomes of 79 patients with periprosthetic hip fractures around cemented tapered polished stem (CTPS) implants treated with osteosynthesis between January 1997 and July 2011. All patients underwent open reduction and fixation using a broad dynamic compression plate (DCP). Seventy two (91%) of fractures united. There were seven (9%) non-unions with failure of metal work, three (4%) as a result of infection and four (5%) due to mechanical failure. Significant subsidence (>5mm) of the implant was seen in seven (9%) of cases...
July 12, 2017: Injury
https://www.readbyqxmd.com/read/28735216/elastic-properties-and-strain-to-crack-initiation-of-calcium-phosphate-bone-cements-revelations-of-a-high-resolution-measurement-technique
#6
Ingrid Ajaxon, Alice Acciaioli, Giacomo Lionello, Maria-Pau Ginebra, Caroline Öhman-Mägi, Massimiliano Baleani, Cecilia Persson
Calcium phosphate cements (CPCs) should ideally have mechanical properties similar to those of the bone tissue the material is used to replace or repair. Usually, the compressive strength of the CPCs is reported and, more rarely, the elastic modulus. Conversely, scarce or no data are available on Poisson's ratio and strain-to-crack-initiation. This is unfortunate, as data on the elastic response is key to, e.g., numerical model accuracy. In this study, the compressive behaviour of brushite, monetite and apatite cements was fully characterised...
June 21, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28735201/ultrasound-elastography-of-the-prostate-using-an-unconstrained-modulus-reconstruction-technique-a-pilot-clinical-study
#7
REVIEW
Seyed Reza Mousavi, Hassan Rivaz, Gregory J Czarnota, Abbas Samani, Ali Sadeghi-Naini
A novel full-inversion-based technique for quantitative ultrasound elastography was investigated in a pilot clinical study on five patients for non-invasive detection and localization of prostate cancer and quantification of its extent. Conventional-frequency ultrasound images and radiofrequency (RF) data (~5 MHz) were collected during mechanical stimulation of the prostate using a transrectal ultrasound probe. Pre and post-compression RF data were used to construct the strain images. The Young's modulus (YM) images were subsequently reconstructed using the derived strain images and the stress distribution estimated iteratively using finite element (FE) analysis...
July 20, 2017: Translational Oncology
https://www.readbyqxmd.com/read/28735148/mechanically-competent-and-cytocompatible-polycaprolactone-borophosphosilicate-hybrid-biomaterials
#8
Dibakar Mondal, S Jeffrey Dixon, Kibret Mequanint, Amin S Rizkalla
Organic-inorganic class II hybrid materials have domain sizes at the molecular level and chemical bonding between the organic and inorganic phases. We have previously reported the synthesis of class II hybrid biomaterials from alkoxysilane-functionalized polycaprolactone (PCL) and borophosphosilicate (B2O3-P2O5-SiO2) glass (BPSG) through a non-aqueous sol-gel process. In the present study, the mechanical properties and degradability of these PCL/BPSG hybrid biomaterials were studied and compared to those of their conventional composite counterparts...
July 5, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28734691/cerebellar-fits-in-the-2000s
#9
Domenico Serino, Davide Caputo, Lucia Fusco
Acute compression on the brainstem or acute increase in intracranial pressure may induce non-epileptic events varying from tonic seizures to axial rigidity with motor automatism, sometimes clearly characterized by decerebrate or decorticate paroxysmal posturing. The EEG correlate is characterized by diffuse asynchronous slow waves of variable amplitude. The mechanism behind such events, known as "cerebellar seizures or fits", is linked to cerebellar herniation and brainstem compression and is not of cortical origin...
July 19, 2017: Brain & Development
https://www.readbyqxmd.com/read/28734609/reinforcements-in-avian-wing-bones-experiments-analysis-and-modeling
#10
E Novitskaya, C J Ruestes, M M Porter, V A Lubarda, M A Meyers, J McKittrick
Almost all species of modern birds are capable of flight; the mechanical competency of their wings and the rigidity of their skeletal system evolved to enable this outstanding feat. One of the most interesting examples of structural adaptation in birds is the internal structure of their wing bones. In flying birds, bones need to be sufficiently strong and stiff to withstand forces during takeoff, flight, and landing, with a minimum of weight. The cross-sectional morphology and presence of reinforcing structures (struts and ridges) found within bird wing bones vary from species to species, depending on how the wings are utilized...
July 14, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28734296/spherical-harmonics-analysis-of-surface-density-fluctuations-of-spherical-ionic-sds-and-nonionic-c12e8-micelles-a-molecular-dynamics-study
#11
Noriyuki Yoshii, Yuki Nimura, Kazushi Fujimoto, Susumu Okazaki
The surface structure and its fluctuation of spherical micelles were investigated using a series of density correlation functions newly defined by spherical harmonics and Legendre polynomials based on the molecular dynamics calculations. To investigate the influence of head-group charges on the micelle surface structure, ionic sodium dodecyl sulfate and nonionic octaethyleneglycol monododecylether (C12E8) micelles were investigated as model systems. Large-scale density fluctuations were observed for both micelles in the calculated surface static structure factor...
July 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28734257/comparison-of-femoropopliteal-artery-stents-under-axial-and-radial-compression-axial-tension-bending-and-torsion-deformations
#12
Kaspars Maleckis, Paul Deegan, William Poulson, Cole Sievers, Anastasia Desyatova, Jason MacTaggart, Alexey Kamenskiy
High failure rates of Peripheral Arterial Disease (PAD) stenting appear to be associated with the inability of certain stent designs to accommodate severe biomechanical environment of the femoropopliteal artery (FPA) that bends, twists, and axially compresses during limb flexion. Twelve Nitinol stents (Absolute Pro, Supera, Lifestent, Innova, Zilver, Smart Control, Smart Flex, EverFlex, Viabahn, Tigris, Misago, and Complete SE) were quasi-statically tested under bench-top axial and radial compression, axial tension, bending, and torsional deformations...
July 13, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28734256/3d-porous-polyurethanes-featured-by-different-mechanical-properties-characterization-and-interaction-with-skeletal-muscle-cells
#13
Lorenzo Vannozzi, Leonardo Ricotti, Tommaso Santaniello, Tercio Terencio, Reinier Oropesa-Nunez, Claudio Canale, Francesca Borghi, Arianna Menciassi, Cristina Lenardi, Irini Gerges
The fabrication of biomaterials for interaction with muscle cells has attracted significant interest in the last decades. However, 3D porous scaffolds featured by a relatively low stiffness (almost matching the natural muscle one) and highly stable in response to cyclic loadings are not available at present, in this context. This work describes 3D polyurethane-based porous scaffolds featured by different mechanical properties. Biomaterial stiffness was finely tuned by varying the cross-linking degree of the starting foam...
July 14, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28733922/effect-of-collagen-fibre-orientation-on-intervertebral-disc-torsion-mechanics
#14
Bo Yang, Grace D O'Connell
The intervertebral disc is a complex fibro-cartilaginous material, consisting of a pressurized nucleus pulposus surrounded by the annulus fibrosus, which has an angle-ply structure. Disc injury and degeneration are noted by significant changes in tissue structure and function, which significantly alters stress distribution and disc joint stiffness. Differences in fibre orientation are thought to contribute to changes in disc torsion mechanics. Therefore, the objective of this study was to evaluate the effect of collagen fibre orientation on internal disc mechanics under compression combined with axial rotation...
July 21, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28732916/preparation-and-characterization-of-hybrid-double-network-chitosan-poly-acrylic-amide-acrylic-acid-high-toughness-hydrogel-through-al-3-crosslinking
#15
Xiancai Jiang, Nanping Xiang, Jinquan Wang, Yulai Zhao, Linxi Hou
Development of bio-based hydrogels with good mechanical properties is of great importance for their excellent biocompatibility and biodegradability. In this paper, chitosan (CS) based double network (DN) hydrogel was prepared by dissolving CS in AlCl3·6H2O aqueous solution instead of acetic acid solution. After dissolving acrylic amide (AM), acrylic acid (AA), N, N'-methylenebisacrylamide and 2-hydroxy-4'-(2-hydoxyethoxy)-2-methylpropiophenone were added into the CS/Al(3+) solution and the CS/PAMAA-Al(3+) DN hydrogel was prepared by UV polymerization...
October 1, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28731224/extremely-low-density-and-super-compressible-graphene-cellular-materials
#16
Ling Qiu, Bing Huang, Zijun He, Yuanyuan Wang, Zhiming Tian, Jefferson Zhe Liu, Kun Wang, Jingchao Song, Thomas R Gengenbach, Dan Li
Development of extremely low density graphene elastomer (GE) holds the potential to enable new properties that traditional cellular materials cannot offer, which are promising for a range of emerging applications, ranging from flexible electronics to multifunctional scaffolds. However, existing graphene foams with extremely low density are generally found to have very poor mechanical resilience. It is scientifically intriguing but remains unresolved whether and how the density limit of this class of cellular materials can be further pushed down while their mechanical resilience is being retained...
July 21, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28731145/piezo1-protein-induces-the-apoptosis-of-human-osteoarthritis-derived-chondrocytes-by-activating-caspase-12-the-signaling-marker-of-er-stress
#17
Xiao-Fei Li, Zhao Zhang, Zhu-Ke Chen, Zhao-Wei Cui, Hai-Ning Zhang
The present study was carried out to determine whether the mechanically activated cation channel Piezo1 protein plays a role as a signaling pathway which causes the apoptosis of human chondrocytes. The chondrocytes were isolated, cultured, and then subjected to mechanical stretch force for 0, 2, 12, 24 and 48 h, respectively. The expression levels of Piezo1 and the apoptosis-related protein caspase-12 were assessed by reverse transcription-quantitative polymerase chain reaction, as well as the apoptosis-related genes, B cell lymphoma/leukemia-2 (Bcl-2), Bcl-associated X protein (Bax) and Bcl-2-associated death promoter (BAD)...
July 19, 2017: International Journal of Molecular Medicine
https://www.readbyqxmd.com/read/28730803/3d-graphene-foam-filled-elastomer-composites-with-high-thermal-and-mechanical-properties
#18
Haoming Fang, Yunhong Zhao, Yafei Zhang, Yanjuan Ren, Shulin Bai
In order to meet the increasing demands for effective heat management of electronic devices, graphene based polymeric composite is considered to be one of the candidate materials due to the ultrahigh thermal conductivity of graphene. However, poor graphene dispersion, low quality of exfoliated graphene and strong phonon scattering at graphene/matrix interface restrict the heat dissipation ability of graphene filled composites. Here, a facile and versatile approach to bond graphene foam (GF) with polydimethylsiloxane (PDMS) is proposed and the corresponding composite with considerable improvement of thermal conductivity and insulativity is fabricated...
July 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28730506/hiatus-hernia-as-a-cause-of-dysphagia
#19
REVIEW
Hamish Philpott, Rami Sweis
PURPOSE OF REVIEW: This review aims to discuss the putative relationship between hiatus hernia and dysphagia. RECENT FINDINGS: Proposed mechanisms of dysphagia in patients with hiatus hernia are usually difficult to identify, but recent advances in technology (high-resolution manometry with or without concomitant impedance, ambulatory pH with impedance, videofluoroscopy, and the endoluminal functional lumen imaging probe (EndoFLIP)) and methodology (inclusion of swallows of various consistencies and volumes or shifting position during the manometry protocol) can help induce symptoms and identify the underlying disorder...
August 2017: Current Gastroenterology Reports
https://www.readbyqxmd.com/read/28729605/evaluating-the-effects-of-material-properties-of-artificial-meniscal-implant-in-the-human-knee-joint-using-finite-element-analysis
#20
Duraisamy Shriram, Gideon Praveen Kumar, Fangsen Cui, Yee Han Dave Lee, Karupppasamy Subburaj
Artificial meniscal implants may replace severely injured meniscus and restore the normal functionality of the knee joint. Implant material stiffness and shape influence the longevity of implantations. This study, using 3D finite element analysis, aimed to evaluate the effects of material stiffness variations of anatomically shaped artificial meniscal implant in the knee joint. Finite element simulations were conducted on five different cases including intact knee, medial meniscectomized knee, and the knee joint with the meniscal implant with three distinct material stiffness...
July 20, 2017: Scientific Reports
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