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differential geometry

Wim M van Rees, Elisabetta A Matsumoto, A Sydney Gladman, Jennifer A Lewis, L Mahadevan
Recent progress in additive manufacturing and materials engineering has led to a surge of interest in shape-changing plate and shell-like structures. Such structures are typically printed in a planar configuration and, when exposed to an ambient stimulus such as heat or humidity, swell into a desired three-dimensional geometry. Viewed through the lens of differential geometry and elasticity, the application of the physical stimulus can be understood as a local change in the metric of a two dimensional surface embedded in three dimensions...
October 18, 2018: Soft Matter
Chuang Yu, Alin Deng, Jianjun Ma, Xiaoqing Cai, Cancan Wen
Convention applied to describe contaminant transport in landfills and groundwater systems is typically characterized by simplified geometries and boundary conditions. As a result, they neglect the more general boundary conditions encountered in the real world, including convection and diffusion of contaminants (e.g., landfill leachate) associated with fluid transportation in the lateral direction. Here, we present semi-analytical solutions that can be used to describe and estimate the contaminants' fate in two-dimensional space...
October 15, 2018: Environmental Science and Pollution Research International
Cacie Hart, Avra Kundu, Kowsik Kumar, Sreekanth J Varma, Jayan Thomas, Swaminathan Rajaraman
Adverse cardiac events are a major cause of late-stage drug development withdrawals. Improved in vitro systems for predicting cardiotoxicity are of great interest to prevent these events and to reduce the expenses involved in the introduction of cardiac drugs into the marketplace. Interdigitated electrodes (IDEs) affixed with a culture well provide a simple, suitable solution for in vitro analysis of cells because of their high sensitivity, ease of fabrication, and label-free, nondestructive analysis. Culturing human pluripotent stem cell differentiated cardiomyocytes onto these IDEs allows for the use of the IDE⁻cell combination in predictive toxicity assays...
October 11, 2018: Biosensors
R Martin, D J Chappell, N Chuzhanova, J J Crofts
Despite the highly convoluted nature of the human brain, neural field models typically treat the cortex as a planar two-dimensional sheet of ne;urons. Here, we present an approach for solving neural field equations on surfaces more akin to the cortical geometries typically obtained from neuroimaging data. Our approach involves solving the integral form of the partial integro-differential equation directly using collocation techniques alongside efficient numerical procedures for determining geodesic distances between neural units...
October 11, 2018: Journal of Computational Neuroscience
Nikhil Narang, Jayant Raikhelkar, Gabriel Sayer, Nir Uriel
Left ventricular assist devices (LVAD) provide a durable option for patients with advanced hear failure. Axial and centrifugal pump physiology differs with regard to the relationship between pump inflow-outflow cannula pressure differential and flow, which results in device behavior that can vary drastically under different loading conditions. Ramp studies can aid the clinician in choosing the optimal speed to adequately unload the left ventricle. Advances in 3-dimensional echocardiography enhance the understanding of chamber geometry for both types of LVADs...
November 2018: Cardiology Clinics
A Ali, J E-Y Lee
We present a unique lateral shear resonance mode excited in a micro-electro-mechanical (MEM) disk resonator. We refer to this proposed mode as the Button-like (BL) mode. The BL mode has a characteristic lateral strain profile (based on the sum of orthogonal strain components in the plane of fabrication) resembles a shirt button. Hence our choice of name for this mode. The strain profile of the BL mode is highly suited for piezoelectric transduction. Like the more widely reported Wine Glass (WG) or elliptical mode, the BL mode offers feedthrough cancellation through fully-differential transduction...
October 5, 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Siddhartha Das, Jayesh R Bellare
Dental pulp stem cells (DPSCs) are adult multipotent stem cells of neuroectodermal origin; they provide an encouraging perspective in the domain of nerve tissue engineering. DPSCs could be transplanted in biodegradable electrospun neuro-supportive scaffold (optimized in various 3D geometries like coating on the surface of titanium implant, hollow/solid tubes, etc.) for enhanced in vivo recovery of peripheral nerves. Herein, we describe the fabrication of uniform bead-free nanofibrous scaffold which supports DPSCs, proliferation, and their subsequent neural differentiation and thus could be utilized for enhanced regeneration of peripheral nervous system...
October 8, 2018: Methods in Molecular Biology
Thi Thanh-Ngan Nguyen, Thanh-Truc Vo, Bich Ngoc-Huong Nguyen, Dinh-Truong Nguyen, Van-Su Dang, Chi-Hien Dang, Thanh-Danh Nguyen
This study presents an efficient and facile method for biosynthesis of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using aqueous extract of burdock root (BR), A. lappa, and their applications. The nanoparticles were characterized by ultraviolet-visible spectrophotometry, X-ray diffraction, transmission electron microscopy, energy dispersive X-ray, thermogravimetry, and differential thermal analysis. AgNPs capped the BR extract (BR-AgNPs) possessed roughly spherical geometry with an average diameter of 21...
October 6, 2018: Environmental Science and Pollution Research International
Seyedehsamaneh Shojaeilangari, C Ross Schmidtlein, Arman Rahmim, Mohammad Reza Ay
PURPOSE: Robust and reliable reconstruction of images from noisy and incomplete projection data holds significant potential for proliferation of cost-effective medical imaging technologies. Since conventional reconstruction techniques can generate severe artifacts in the recovered images, a notable line of research constitutes development of appropriate algorithms to compensate for missing data and to reduce noise. In the present work, we investigate the effectiveness of state-of-the-art methodologies developed for image inpainting and noise reduction to preserve the quality of reconstructed images from under-sampled PET data...
October 4, 2018: Medical Physics
Z Lee, U Kaiser, H Rose
The annular differential phase contrast (ADPC) mode in a third-order spherical aberration-corrected scanning transmission electron microscope (STEM) has recently been realized at an operating voltage of 300 kV by inserting a physical Fresnel phase plate in front of the objective lens and by using a detector geometry which matches that of the Fresnel phase plate [1]. By image calculation we explore the feasibility of this mode for the voltage range of 20-80kV. Alternatively, we mimic the Fresnel phase plate material-free with the help of the adjustable aberrations of the corrector...
September 26, 2018: Ultramicroscopy
Bradly Alicea, Richard Gordon
One overarching principle of eukaroytic development is the generative spatial emergence and self-organization of cell populations. As cells divide and differentiate, they and their descendents form a spatiotemporal explicit and increasingly compartmentalized complex system. Yet despite this comparmentalization, there is selective functional overlap between these structural components. While contemporary tools such as lineage trees and molecular signaling networks prvide a window into this complexity, they do not characterize embryogenesis as a global process...
September 29, 2018: Bio Systems
L B Sukhodub, L F Sukhodub, Yu I Prylutskyy, N Yu Strutynska, L L Vovchenko, V M Soroca, N S Slobodyanik, N G Tsierkezos, U Ritter
The novel bioactive composite material based on hydroxyapatite and multi-walled carbon nanotubes filled by iron was synthesized by the "wet chemistry" method and characterized in detail by various experimental techniques including the X-ray diffraction, Fourier transform infrared and energy-dispersive X-ray fluorescence spectroscopy, thermogravimetric and differential thermal analysis. The swelling behaviour was quantified by measuring the changes in sample weight as a function of sample immersion time in a phosphate buffered saline (PBS)...
December 1, 2018: Materials Science & Engineering. C, Materials for Biological Applications
Shoichiro Sumi, Masako Kawagoe, Rie Abe, Goichi Yanai, Kai-Chiang Yang, Yasumasa Shirouzu
Introduction: Formation of cell spheres is an important procedure in biomedical research. A large number of high-quality cell spheres of uniform size and shape are required for basic studies and therapeutic applications. Conventional approaches, including the hanging drop method and suspension culture, are used for cell sphere production. However, these methods are time consuming, cell spheres cannot be harvested easily, and it is difficult to control the size and geometry of cell spheres...
December 2017: Regenerative Therapy
Benjamin T Wilks, Elisabeth B Evans, Morcos N Nakhla, Jeffrey R Morgan
Extracellular matrix composition and organization play a crucial role in numerous biological processes ranging from cell migration, differentiation, survival and metastasis. Consequently, there have been significant efforts towards the development of biomaterials and in vitro models that recapitulate the complexity of native tissue architecture. Here, we demonstrate an approach to fabricating highly aligned cell-derived tissue constructs via the self-assembly of human dermal fibroblasts. By optimizing mold geometry, cell seeding density, and media composition we can direct human dermal fibroblasts to adhere to one another around a non-adhesive agarose peg to facilitate the development of cell-mediated circumferential tension...
September 26, 2018: Acta Biomaterialia
Cristina Falcinelli, Zhi Li, Wilfred W Lam, Greg J Stanisz, Anne M Agur, Cari M Whyne
Accurate characterization of the craniomaxillofacial (CMF) skeleton using finite element (FE) modeling requires representation of complex geometries, heterogeneous material distributions, and physiological loading. Musculature in CMF FE models are often modeled with simple link elements that do not account for fiber bundles (FBs) and their differential activation. Magnetic resonance (MR) diffusion-tensor imaging (DTI) enables reconstruction of the three-dimensional (3D) FB arrangement within a muscle. However, 3D quantitative validation of DTI-generated FBs is limited...
November 1, 2018: Journal of Biomechanical Engineering
Karthik Damodaran, Saradha Venkatachalapathy, Farid Alisafaei, A V Radhakrishnan, Doorgesh Sharma Jokhun, Vivek B Shenoy, G V Shivashankar
Fibroblasts exhibit heterogeneous cell geometries in tissues and integrate both mechanical and biochemical signals in their local microenvironment to regulate genomic programs via chromatin remodelling. While in connective tissues fibroblasts experience tensile and compressive forces (CFs), the role of compressive forces in regulating cell behaviour and in particular, the impact of cell geometry in modulating transcriptional response to such extrinsic mechanical forces is unclear. Here, we show that CF on geometrically well-defined mouse fibroblast cells reduces actomyosin contractility and shuttles Histone Deacetylase 3 (HDAC3), into the nucleus...
September 26, 2018: Molecular Biology of the Cell
Kristine T Taniguchi, Trent W Biggs, Eddy J Langendoen, Carlos Castillo, Napoleon Gudino-Elizondo, Yongping Yuan, Douglas Liden
Urbanization can lead to accelerated stream channel erosion, especially in areas experiencing rapid population growth, unregulated urban development on erodible soils, and variable enforcement of environmental regulations. A combination of field surveys and Structure-from-Motion (SfM) photogrammetry techniques was used to document spatial patterns in stream channel geometry in a rapidly urbanizing watershed, Los Laureles Canyon (LLCW), in Tijuana, Mexico. Ground-based SfM photogrammetry was used to map channel dimensions with 1 to 2 cm vertical mean error for four stream reaches (100-300 m long) that were highly variable and difficult to survey with a differential GPS...
June 15, 2018: Earth surface processes and landforms
Michael Whitely, Stacy Cereceres, Prachi Dhavalikar, Karim Salhadar, Thomas Wilems, Brandon Smith, Antonios Mikos, Elizabeth Cosgriff-Hernandez
The design of tissue engineered scaffolds based on polymerized high internal phase emulsions (polyHIPEs) has emerged as a promising bone grafting strategy. We previously reported the ability to 3D print emulsion inks to better mimic the structure and mechanical properties of native bone while precisely matching defect geometry. In the current study, redox-initiated hydrogel carriers were investigated for in situ delivery of human mesenchymal stem cells (hMSCs) utilizing the biodegradable macromer, poly(ethylene glycol)-dithiothreitol...
December 2018: Biomaterials
Barbara Miroslaw, Beata Cristóvão, Zbigniew Hnatejko
New PdII ⁻LnIII ⁻PdII complexes of hexadentate N₂O₄ Schiff base ligand (H₄L: N , N '-bis(2,3-dihydroxybenzylidene)-1,3-diamino-2,2-dimethylpropane) with Eu ( 1 ), Tb ( 2 ), Er ( 3 ) and Yb ( 4 ) ([Pd₂Eu(H₂L)₂NO₃](NO₃)₂∙2H₂O∙2CH₃OH 1 , [Pd₂Ln(H₂L)₂H₂O](NO₃)₃∙3H₂O, where Ln = Tb 2 , Er 3 , [Pd₂Yb(H₂L)₂H₂O](NO₃)₃∙5.5H₂O 4 ) were synthesized and characterized structurally and physicochemically by thermogravimetry (TG), differential thermogravimetry (DTG), differential scanning calorimetry (DSC) and luminescence measurements...
September 21, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Arnaud Bruyas, Seyedsina Moeinzadeh, Sungwoo Kim, David W Lowenberg, Yunzhi Peter Yang
3D printing of composite materials such as polycaprolactone/beta-tricalcium phosphate (PCL/β-TCP) enables the design and manufacturing of scaffolds with advanced geometries, along with improved physical and biological properties for large bone defect repair. Terminal sterilization of the scaffolds is inevitable for clinical applications. Electron beam (E-beam) is non-toxic, and can be used for sterilizing heat sensitive scaffolds by the use of high radiation dose in a short period of time. In this paper, we assessed the influence of E-beam sterilization on the properties of 3D printed PCL/β-TCP scaffolds, focusing on the key physical and biological properties for bone tissue engineering...
September 20, 2018: Tissue Engineering. Part A
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