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Wyszukujesz frazę "Fleming, P. D." wg kryterium: Autor


Wyświetlanie 1-4 z 4
Tytuł:
Design and testing 3D printed structures for bone replacements
Autorzy:
Ikonomov, P. G.
Yahamed, A.
Fleming, P. D.
Pekarovicova, A.
Powiązania:
https://bibliotekanauki.pl/articles/367249.pdf
Data publikacji:
2020
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
3D printing
bone structure
3D modelling
testing
mechanical properties
druk 3D
struktura kości
modelowanie 3D
badania
właściwości mechaniczne
Opis:
Purpose: 3D printing has shown enormous potential for building plastic products, including bone, organs, and body parts. The technology has progressed from visualization and preoperation training to the 3D printing of customized body parts and implants. This research aims to create 3D printed bone structure from plastics and test the mechanical properties of the cortical and trabecular bone structures if they match the real bone structure strength. Design/methodology/approach: We used Digital Imaging, and Communications in Medicine (DICOM) images from Computer Tomography (CT) scans to created external bone structures. These images' resolution did not allow the creation of fine trabecular bone structures, so we used 3D modeling software to engineer special 3D void honeycomb structures (with triangular, square, and hexagonal shapes). Another reason to design void structures is that the 3D printing of complex shapes without support materials is problematic. After designing and 3D printing of the 3D bone structures, their mechanical properties need to be tested. Findings: 3D bone models, solid (cortical), and void (trabecular) bone structures were designed, 3D printed, and then tested. Tensile, bending, and compression testing was performed. Testing the mechanical properties of the honeycomb structures (triangular, square, and hexagonal) shows that their strength and modulus are higher than those of the real trabecular bones. The results show that 3D printed honeycomb structures mechanical properties can match and some cases exceeding the properties of the actual bones trabecular structures, while the sold structures have lower mechanical properties than the bone cortical structures. Research limitations/implications: During the 3D printing experiments, we found that 3D printers, in general, have low resolution, not enough to print fine trabecular bone structures. To solve the existing 3D printing technology's insufficient resolution, we later designed and built an SLA (stereolithography) 3D printer with high printing resolution (10 micrometers). Another limitation we found is the lack of biocompatible materials for 3D printing of bone structures. Future research work is in progress formulating superior ink/resin for bone structures 3D printing. Further, clinical trials need to be performed to investigate 3D printed parts’ influence on the healing of bone structures. Practical implications: We found that the 3D void (honeycomb) structures will have an impact not only on building bone structures but also in engineering special structures for industrial applications that can reduce the weight, time, and the cost of the material, while still keep sufficient mechanical properties. Originality/value: Designing and testing 3D printed bone models, solid (cortical), and void (trabecular) bone structures could replace bones. Design and test special void honeycomb structures as a replacement for cortical bone structures.
Źródło:
Journal of Achievements in Materials and Manufacturing Engineering; 2020, 101, 2; 76-85
1734-8412
Pojawia się w:
Journal of Achievements in Materials and Manufacturing Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Light Harvesting Process in Purple Bacteria
Autorzy:
Krueger, B. P.
Scholes, G. D.
Yu, J.- Y.
Fleming, G. R.
Powiązania:
https://bibliotekanauki.pl/articles/1993667.pdf
Data publikacji:
1999-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.15.Mi
82.20.Rp
42.50.Md
Opis:
We present and review the results of fluorescence upconversion and photon echo experiments, and $ab initio$ calculations performed in our group within the last few years with respect to the light harvesting process in purple bacteria. Carotenoids transfer energy to bacteriochlorophyll (BChl) mainly via the carotenoid S$\text{}_{2}$ → BChl Q$\text{}_{x}$ pathway on a ~100 fs timescale. This transfer is reasonably reproduced by considering the Coulombic coupling calculated using the transition density cube method which is valid at all molecular separations. Carotenoids may also serve a role in mediating B800 → B850 energy transfer in LH2 by perturbing the transition density of the B850 as shown by ab initio calculations on a supermolecule of two B850 BChls, one carotenoid and one B800 BChl. Further calculations on dimers of B850 BChl estimate the intra- and interpolypeptide coupling to be 315 and 245 cm$\text{}^{-1}$, respectively. These interactions are dominated by Coulombic coupling, while the orbital overlap dependent coupling is ~20% of the total. Photon echo peak shift experiments (3PEPS) on LH1 and the B820 subunit are quantitatively simulated with identical parameters aside from an energy transfer time of 90 fs in LH1 and ∞ in B820, suggesting that excitation is delocalized over roughly two pigments in LH1. 3PEPS data taken at room and low temperature (34 K) on the B800-B820 suggest that static disorder is the dominant mechanism localizing excitation in LH1 and LH2. We suggest that the competition between the delocalizing effects of strong electronic coupling and the localizing effects of disorder and nuclear motion results in excitation in the B850 and B875 rings being localized on 2-4 pigments within approximately 60 fs.
Źródło:
Acta Physica Polonica A; 1999, 95, 1; 63-83
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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