11,402 results match your criteria geometry parameters

Particle tracking and beam optics analysis on a toroidal gantry for proton therapy.

Phys Med Biol 2021 Apr 13. Epub 2021 Apr 13.

SCI-IC-BD, Ecole Polytechnique Fédérale de Lausanne, Station 14, Lausanne, 1015, SWITZERLAND.

GaToroid is a concept of toroidal gantry for hadron therapy under investigation at CERN. It makes use of the toroidal magnetic field between each pair of coils to steer and focus the particle beams down to the patient. This peculiar concept requires detailed studies on particle tracking and beam optics to optimize the winding geometry and explore the properties of the system. Read More

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Three-dimensional nanolithography guided by DNA modular epitaxy.

Nat Mater 2021 Apr 12. Epub 2021 Apr 12.

Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA.

Lithographic scaling of periodic three-dimensional patterns is critical for advancing scalable nanomanufacturing. Current state-of-the-art quadruple patterning or extreme-ultraviolet lithography produce a line pitch down to around 30 nm, which might be further scaled to sub-20 nm through complex post-fabrication processes. Herein, we report the use of three-dimensional (3D) DNA nanostructures to scale the line pitch down to 16. Read More

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Correlation between Second Ionization Potential and Nonlinear Optical Properties of Bivalent Transition-Metal Complexes: A Quantum Chemical Study.

Inorg Chem 2021 Apr 12. Epub 2021 Apr 12.

Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5280, Institut des Sciences Analytiques, 69622 Villeurbanne Cedex, France.

Discovering new materials with excellent nonlinear optical responses has recently become a very interesting research topic in the different domains of materials science. Currently, density functional theory (DFT) has been shown to be a powerful tool in the explanation and prediction of the performance of novel nonlinear optical (NLO) materials. Quantum chemical calculations using DFT/TD-DFT with the B3LYP exchange-correlation functional are reported to study the NLO properties of 26 bivalent transition-metal (TM) complexed by six acyclic hexadentate ligands providing pyridyl/pyrazine-amide-thioether/ether coordination and differing by the nature of the methylene dichalcogenate spacer between the rings. Read More

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Size effect of the guest cation on the AlO framework in aluminate sodalite-type oxides M[AlO](SO) (M = Sr and Ca) in the I43m phase.

Acta Crystallogr B Struct Sci Cryst Eng Mater 2021 Apr 25;77(Pt 2):186-192. Epub 2021 Feb 25.

Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8526, Japan.

Sr[AlO](SO) (SAS) and Ca[AlO](SO) (CAS) are members of the aluminate sodalite-type oxides with the general chemical formula M[AlO](XO) (M is the guest cation and XO is the guest anion). To discuss the role of the guest cations (M = Sr and Ca) on the rotation of AlO in the oxygen tetrahedral framework in the I43m phase, the crystal structure parameters and the probability density function of the guest ions in SAS and CAS have been investigated via synchrotron radiation X-ray powder diffraction by considering Gram-Charlier expansions. The interatomic distances between the M and O ions evaluated from the maximum positions in the probability density distribution are almost equal to the sum of the ideal ionic radii of the M and O ions. Read More

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A high-resolution life cycle impact assessment model for continental freshwater habitat change due to water consumption.

Sci Total Environ 2021 Mar 22;782:146664. Epub 2021 Mar 22.

ITAP, Univ Montpellier, INRAE, Institut Agro, Montpellier, France; Elsa, Research Group for Environmental Lifecycle and Sustainability Assessment, Montpellier, France; GIRO Program, Institute of Agrifood Research and Technology (IRTA), Torre Marimon, 08140 Caldes de Montbui, Barcelona, Spain.

Global value chains and climate change have a significant impact on water resources and increasingly threaten freshwater ecosystems. Recent methodological proposals for life cycle impact assessment (LCIA), evaluate water use impacts on freshwater habitats based on river hydraulic parameters alterations. However, they are limited to French rivers due to lack of global data and models. Read More

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The Effect of Geometric and Hemodynamic Parameters on Blood Flow Efficiency in Repaired Tetralogy of Fallot Patients.

Ann Biomed Eng 2021 Apr 9. Epub 2021 Apr 9.

Institute of Biomedical Engineering, University of Toronto, Toronto, Canada.

Surgical repair of Tetralogy of Fallot (TOF) involves a series of steps to remove right ventricular outflow tract and pulmonary artery obstruction. However, the large degree of anatomic variability among preoperative TOF patients may impact the effectiveness of different repair strategies and, subsequently, different geometric modifications for different patients. This study investigates the relationships between geometric and hemodynamic parameters and mechanical energy efficiency for a patient-specific dataset of 16 postoperative TOF repairs, using morphometric and statistical shape analyses, as well as computational fluid dynamics simulations with physiologically-relevant inlet and outlet boundary conditions. Read More

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A random parameter negative binomial model for signalized intersection accidents in Seoul, Korea.

Int J Inj Contr Saf Promot 2021 Apr 9:1-11. Epub 2021 Apr 9.

Department of Transportation Engineering and Department of Smart Cities, University of Seoul, Seoul, Korea.

A variety of statistical models were generally considered to better understand the relationship between crash occurrences and diverse factors. However, most of statistical models adapted fixed parameters which cannot incorporate time variation or sement-specific effects. To relieve this problem, this study focuses on a traffic accident frequency model using a random parameter negative binomial approach. Read More

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The influence of biophysical parameters in a biomechanical model of cortical folding patterns.

Sci Rep 2021 Apr 8;11(1):7686. Epub 2021 Apr 8.

IMT Atlantique, LaTIM U1101 INSERM, UBL, Brest, France.

Abnormal cortical folding patterns, such as lissencephaly, pachygyria and polymicrogyria malformations, may be related to neurodevelopmental disorders. In this context, computational modeling is a powerful tool to provide a better understanding of the early brain folding process. Recent studies based on biomechanical modeling have shown that mechanical forces play a crucial role in the formation of cortical convolutions. Read More

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Dimensional scaling of thin-film stimulation electrode systems in translational research.

J Neural Eng 2021 Apr 8. Epub 2021 Apr 8.

LSBI, Ecole Polytechnique Federale de Lausanne, Station 17, Lausanne, 1015, SWITZERLAND.

Objective: Electrical stimulation of biological tissue is an established technique in research and clinical practice that uses implanted electrodes to deliver electrical pulses for a variety of therapies. Significant research currently explores new electrode system technologies and stimulation protocols in preclinical models, aiming at both improving the electrode performance and confirming therapeutic efficacy. Assessing the scalability of newly proposed electrode technology and their use for tissue stimulation remains, however, an open question. Read More

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Additively manufactured Ti-6Al-4V thin struts via laser powder bed fusion: Effect of building orientation on geometrical accuracy and mechanical properties.

J Mech Behav Biomed Mater 2021 Mar 27;119:104495. Epub 2021 Mar 27.

Department of Industrial Engineering - DII, University of Trento, Trento, Italy.

Porous metal lattice structures have a very high potential in biomedical applications, setting as innovative new generation prosthetic devices. Laser powder bed fusion (L-PBF) is one of the most widely used additive manufacturing (AM) techniques involved in the production of Ti6Al4V lattice structures. The mechanical and failure behavior of lattice structures is strongly affected by geometrical imperfections and defects occurring during L-PBF process. Read More

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Coexistence of Two Different Distorted Octahedral [MnF6]3- Sites in K3[MnF6]: Manifestation in Spectroscopy and Magnetism.

Chemistry 2021 Apr 8. Epub 2021 Apr 8.

Universitat Innsbruck, Institut für Allgemeine, Anorganische und Theoretische Chemie, Innrain 80-82, 6020, Innsbruck, AUSTRIA.

As a consequence of the static Jahn-Teller effect of the  5 E ground state of Mn(III) in cubic structures with octahedral parent geometries, their octahedral coordination spheres become distorted. In the case of six fluorido ligands, [MnF 6 ] 3- anions with two longer and four shorter Mn-F bonds comprising elongated octahedra are usually observed. Here, we report the synthesis of the compound K 3 [MnF 6 ]  via  a high-temperature approach and its crystallization by a high-pressure/high-temperature route. Read More

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Design, metallurgical features, mechanical performance and canal preparation of six reciprocating instruments.

Int Endod J 2021 Apr 8. Epub 2021 Apr 8.

Dental Specialty Center, Brazilian Military Police, Minas Gerais, Brazil.

Aim: To compare 6 reciprocating instruments regarding their geometric design, metallurgical characteristics, mechanical behavior and canal preparation.

Methodology: A total of 246 new 25-mm NiTi instruments (41 per group) from 6 reciprocating systems (Reciproc, Reciproc Blue, One Files, One Files Blue, Reverso Silver, and WaveOne Gold) were evaluated throughout a multimethod approach regarding their design using stereomicroscopy (number of blades and helix angle) and scanning electron microscopy (blades symmetry, cross-section, and surface finishing), nickel-titanium composition, phase transformation temperatures, mechanical performance (cyclic fatigue, torsional and bending resistance), and unprepared surface area on anatomically-matched mandibular molars assessed by micro-CT. One-way ANOVA and post hoc Tukey or Mood's median tests were selected depending on sample distribution with significance level set at 5%. Read More

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Assessment of 10-Year Left-Ventricular-Remodeling by CMR in Patients Following Aortic Valve Replacement.

Front Cardiovasc Med 2021 22;8:645693. Epub 2021 Mar 22.

Department of Internal Medicine & Cardiology, German Heart Center Berlin, Berlin, Germany.

Aortic valve replacement (AVR) may result in reverse cardiac remodeling. We aimed to assess long-term changes in the myocardium following AVR by Cardiac Magnetic Resonance Imaging (CMR). We prospectively observed the long-term left ventricular (LV) function and structure of 27 patients with AVR [ = 19 with aortic stenosis (AS); = 8 with aortic regurgitation (AR)] by CMR. Read More

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Purification of propylene and ethylene by a robust metal-organic framework mediated by host-guest interactions.

Angew Chem Int Ed Engl 2021 Apr 7. Epub 2021 Apr 7.

The University of Manchester, chemistry, UNITED KINGDOM.

Industrial purification of propylene and ethylene requires cryogenic distillation and selective hydrogenation over palladium catalysts to remove propane, ethane and/or trace amounts of acetylene. Here, we report the excellent separation of equimolar mixtures of propylene/propane and ethylene/ethane, and of a 1/100 mixture of acetylene/ethylene by a highly robust microporous material, MFM-520, under dynamic conditions. In situ synchrotron single crystal X-ray diffraction, inelastic neutron scattering and analysis of adsorption thermodynamic parameters reveal that a series of synergistic host-guest interactions involving hydrogen bonding and π∙∙∙π stacking interactions underpin the cooperative binding of alkenes within the pore. Read More

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Charge Selectivity of an Ionic Transistor.

Langmuir 2021 Apr 7. Epub 2021 Apr 7.

Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.

The charge selective properties of a long planar nanochannel with an embedded finite uniformly charged section in the middle are studied. The probability flux of a single test ion initially confined to the inlet reservoir is determined by integrating the Smoluchowski equation using a previously published series solution for the Debye-Hückel potential in this geometry. The charge selective properties are characterized by a dimensionless quantity that we call the "fractional blockage". Read More

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The Paramak: automated parametric geometry construction for fusion reactor designs.

F1000Res 2021 18;10:27. Epub 2021 Jan 18.

Culham Centre for Fusion Energy (CCFE), Culham Science Centre, Abingdon, OX14 3DB, UK.

During the conceptual design process of fusion reactors it is useful to rapidly prototype different design concepts and assess their suitability against a range of high level requirements. Rapid prototyping allows the 'fail early' mantra of other fields to be applied to engineering design. Furthermore, the rapid generation of low fidelity analysis allows fast exploration of design space, which enables better decisions to be made during concept selection and the detailed design phase. Read More

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January 2021

Challenges in hemodynamics assessment in complex neurovascular geometries using computational fluid dynamics and benchtop flow simulation in 3D printed patient specific phantoms.

Proc SPIE Int Soc Opt Eng 2021 Feb 15;11600. Epub 2021 Feb 15.

University Dept. of Biomedical Engineering, University at Buffalo, Buffalo, NY.

Purpose: Complex hemodynamics assessments, as those related to carotid stenosis, are not always easily straightforward due to multifaceted challenges presented by the collateral flow in the Circle of Willis (CoW) and brain flow autoregulation. Advanced computational and benchtop methods to investigate hemodynamics aspects related to such complex flows are often used, however both have limitations and could lead to results which may diverge. In this study we investigated these aspects by performing correlated computational fluid dynamics (CFD) simulations and benchtop experiments in patient specific 3D printed phantoms. Read More

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February 2021

Adaptive Remodeling in the Elastase-induced Rabbit Aneurysms.

Exp Mech 2021 Jan 27;61(1):263-283. Epub 2020 Oct 27.

Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 3700 O'Hara Street, Pittsburgh, PA 15261.

Background: Rupture of brain aneurysms is associated with high fatality and morbidity rates. Through remodeling of the collagen matrix, many aneurysms can remain unruptured for decades, despite an enlarging and evolving geometry.

Objective: Our objective was to explore this adaptive remodeling for the first time in an elastase induced aneurysm model in rabbits. Read More

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January 2021

Effect of the Process Parameters on the Adhesive Strength of Dissimilar Polymers Obtained by Multicomponent Injection Molding.

Polymers (Basel) 2021 Mar 26;13(7). Epub 2021 Mar 26.

Nanotechnology Group, Graduate Program in Industrial Engineering, Polytechnic School, Universidade Federal University of Bahia, R. Aristides Novis 2, 6° Andar, Federação, Salvador 40170-115, Brazil.

The growing demand in the consumer market for products with sustainable technologies has motivated new applications using overmolded natural fiber composites. Therefore, studies have been conducted mainly to understand the adhesive properties of overmolded parts. In the present study, a polypropylene (PP) composite with 30% coconut fibers without additives was developed with the aid of a corotating twin screw extruder. Read More

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DFT Studies of Selected Epoxies with Mesogenic Units-Impact of Molecular Structure on Electro-Optical Response.

Int J Mol Sci 2021 Mar 26;22(7). Epub 2021 Mar 26.

Department of Industrial and Materials Chemistry, Faculty of Chemistry, Rzeszow University of Technology, al. Powstańców Warszawy 6, 35-959 Rzeszów, Poland.

Theoretical studies of molecular structure and electric charge distribution were carried out for three epoxy compounds with different mesogenic cores. The compounds exhibit a nematic phase and form polymer networks that are potential bases for various composites. Results were compared to analogous materials with non-polar chains. Read More

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Changes in Electrical Conductance of Polymer Composites Melts Due to Carbon Nanofiller Particles Migration.

Polymers (Basel) 2021 Mar 26;13(7). Epub 2021 Mar 26.

Enikolopov Institute of Synthetic Polymer Materials of RAS, Profsoyuznaya st. 70, 117393 Moscow, Russia.

In this work, the results of investigation of the effect of polymer composite melts electrical conductance increase with time are presented. The conductance time dependencies were obtained for composites based on polypropylene filled with carbon nanoparticles of different types. The dependencies were analyzed to demonstrate the possibility of correlation of the conductance kinetics with different composite parameters, such as the filler geometry. Read More

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CMT Additive Manufacturing Parameters Defining Aluminium Alloy Object Geometry and Mechanical Properties.

Materials (Basel) 2021 Mar 22;14(6). Epub 2021 Mar 22.

Medical Simulation Education Center, Medical School, University of Pecs, Szigeti Street 12, 7624 Pécs, Hungary.

Additive manufacturing technologies based on metal melting use materials mainly in powder or wire form. This study focuses on developing a metal 3D printing process based on cold metal transfer (CMT) welding technology, in order to achieve enhanced productivity. Aluminium alloy test specimens have been fabricated using a special 3D printing technology. Read More

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A Novel Method for the Complex Tube System Reconstruction and Measurement.

Sensors (Basel) 2021 Mar 22;21(6). Epub 2021 Mar 22.

School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China.

Pipe structures are at the base of the entire industry. In the industry structure, heat and vibration are transmitted in each pipe. The minimum distance between each pipe is significant to the security. Read More

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