A diagonal cut through the SiC bulk unit cell: Structure and composition of the 4H-SiC(11¯02) surface

2008 ◽  
Vol 92 (6) ◽  
pp. 061902 ◽  
Author(s):  
C. Virojanadara ◽  
M. Hetzel ◽  
U. Starke
Keyword(s):  
Cell Structure ◽  
Unit Cell ◽  
Unit Cell Structure

scholarly journals Crystallinity fitting using cellulose crystallite models

2014 ◽  
Vol 70 (a1) ◽  
pp. C1135-C1135
Author(s):  
Patrik Ahvenainen ◽  
Ritva Serimaa
Keyword(s):  
Diffraction Pattern ◽  
Cell Structure ◽  
Unit Cell ◽  
Scattering Data ◽  
Crystalline Cellulose ◽  
Two Dimensional ◽  
Cellulose Crystallite ◽  
Cellulose Iβ ◽  
Diffraction Peaks ◽  
Unit Cell Structure

Cellulose is the most abundant biopolymer on Earth and hence it has enormous potential as a source of renewable energy. The nanoscale properties of cellulose are also import for the wood and papermaking industries. The atomic level structure of naturally occurring cellulose Iβ allomorph is well known [1] and this atomistic model is employed in this study for the cellulose unit cell structure. The cellulose crystallinity cannot be measured directly with scattering methods, but the crystallinity of the sample can be estimated by fitting models of crystalline and amorphous contributions to the sample intensity profile. The crystallinity fitting can be enhanced by improving the cellulose fitting model or the amorphous model. We focus on the cellulose crystallite model. The nanoscale level organization of crystalline cellulose in different plant materials is less well established that the unit cell structure of cellulose Iβ. Information on the texture of the sample is obtained efficiently by measuring the sample with a two-dimensional detector. The two-dimensional diffraction pattern can be used to obtain a wealth of information in one measurement, including the crystallite size, crystallite orientation and the crystallinity of the sample. The small size of cellulose crystallites in the wood cell wall limits the information obtainable from the diffraction pattern as the diffraction peaks widen and overlap. The overlapping of certain diffraction peaks can be studied at least qualitatively by computing the diffraction patterns from crystallite models of varying dimensions. Different models for cellulose crystallite have been suggested in the literature, such as the 36 chain model [2]. We investigate how the crystallinity fitting is influenced by the selected cellulose crystallite model and evaluate the suitability of different models to experimental X-ray scattering data of plant material, wood and highly crystalline cellulose.

Structure-unit cell-based approach on three-dimensional representative braided preforms from four-step braiding: Experimental determination of effects of structure-process parameters on predetermined yarn path

2011 ◽  
Vol 82 (3) ◽  
pp. 220-241 ◽  
Author(s):  
Kadir Bilisik ◽  
Nesrin Sahbaz
Keyword(s):  
Cell Structure ◽  
Three Dimensional ◽  
Unit Cell ◽  
Number Of Layers ◽  
Cell Structures ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Surface Angle ◽  
Unit Cell Structure

The aim of this study was to understand the effects of braid pattern and the number of layers on three-dimensional (3D) braided unit cell structures. Various unit cell-based representative 3D braided preforms were developed. Data generated from these structures included unit cell dimensions, yarn angle, and yarn length in the unit cell structures. It was shown that braid patterns affected the 3D braided unit cell structures. The 1 × 1 braid pattern made fully interconnected integral 3D braided unit cell structures, whereas the 2 × 1 braid pattern created disconnected braid layers that were connected to the structures edges. When the number of layers increased, 3D braided unit cell thickness also increased. Braid pattern slightly affected the braider yarn angle, whereas the number of layers did not influence it. It was observed that the number of layers considerably affected the yarn length in the unit cell structure. Increasing the layer number from five to 10 layers created a yarn path in the unit cell edge regions called the ‘multilayer yarn length’. This yarn path was not observed below five-layer 3D braided unit cell structures. In jamming conditions, minimum jamming decreased the width of the unit cell structure, but maximum jamming increased its width. On the other hand, minimum jamming decreased the surface angle of the unit cell structure, whereas maximum jamming increased the surface angle. In addition, it was realized that jamming conditions influenced the density of the unit cell but did not affect the yarn length in the unit cell structures.

scholarly journals Metamaterial Inspired Microstrip Antenna Investigations Using Metascreens

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Muhammad Tauseef Asim ◽  
Mushtaq Ahmed
Keyword(s):  
Low Cost ◽  
Cell Structure ◽  
Unit Cell ◽  
Dual Band ◽  
Impedance Bandwidth ◽  
Radiation Patterns ◽  
Wireless Applications ◽  
Left Handed ◽  
Metamaterial Antenna ◽  
Unit Cell Structure

A dual layer periodically patterned metamaterial inspired antenna on a low cost FR4 substrate is designed, simulated, fabricated, and tested. The eigenmode dispersion simulations are performed indicating the left handed metamaterial characteristics and are tunable with substrate permittivity. The same metamaterial unit cell structure is utilized to fabricate a metascreen. This metascreen is applied below the proposed metamaterial antenna and next used as superstrate above a simple patch to study the effects on impedance bandwidth, gain, and radiation patterns. The experimental results of these antennas are very good and closely match with the simulations. More importantly, the resonance for the proposed metamaterial antenna with metascreen occurs at the left handed (LH) eigenfrequency of the metamaterial unit cell structure. The measured −10 dB bandwidths are 14.56% and 22.86% for the metamaterial antenna with single and double metascreens, respectively. The metascreens over the simple patch show adjacent dual band response. The first and second bands have measured −10 dB bandwidths of 9.6% and 16.66%. The simulated peak gain and radiation efficiency are 1.83 dBi and 74%, respectively. The radiation patterns are also very good and could be useful in the UWB wireless applications.

Insight into the unit cell: Structure of picene thin films on Ag(100) revealed with complementary methods

2016 ◽  
Vol 145 (17) ◽  
pp. 174706 ◽  
Author(s):  
Tobias Huempfner ◽  
Martin Hafermann ◽  
Christian Udhardt ◽  
Felix Otto ◽  
Roman Forker ◽  
...  
Keyword(s):  
Thin Films ◽  
Cell Structure ◽  
Unit Cell ◽  
Complementary Methods ◽  
Insight Into ◽  
Unit Cell Structure

Iron-platinum nanoparticles as multifunctional vehicles in imaging and drug delivery

2016 ◽  
Author(s):  
◽  
Christian Alan Mason
Keyword(s):  
Platinum Nanoparticles ◽  
Cell Structure ◽  
Unit Cell ◽  
Magnetic Characteristics ◽  
X Ray ◽  
Size And Shape ◽  
Iron Platinum ◽  
Icp Ms ◽  
Face Centered ◽  
Unit Cell Structure

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] In the United States alone, approximately 1.6 million people are diagnosed with cancer and over 500,000 people die of cancer each year. According to the American Cancer Society the probability that a male and female will die of cancer are roughly one in four and one in six, respectively. Though current research and development has reduced the mortality rate, the effectiveness of treatment options are severely limited. There has been a rising interest in the literature focused on developing materials with the ability to selectively treat and diagnose a disease or illness. Iron-platinum nanoparticles have great potential as magnetic resonance imaging (MRI) agents. These superparamagnetic materials have been studied as they may offer a better alternative to current materials. Several different mechanisms for their formation have been described, and multiple parameters have been used to control the size and shape of these nanoparticles. Variables such as the amounts of surfactant, heating rates, and concentration of metal precursors were explored. The synthesis produced nanoparticles with a disordered face-centered cubic (fcc) structure, subsequent annealing could be performed to produce the face-centered tetragonal crystal structure. The nanoparticles size and shape were analyzed using transmission electron microscopy (TEM) along with ImageJ software. The results of these syntheses show that the amount of surfactant used during the synthesis has a significant effect on the size and shape of the nanoparticles. The cubic and spheroid shaped nanoparticles were analyzed for variations in unit cell structure, composition, or magnetic properties. The composition of the nanoparticles was analyzed with energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS). Unit cell structure was analyzed using powder X-ray diffraction (XRD). Magnetic measurements were obtained using a 7T MRI instrument. These analyses have shown that the unit cell structure, composition, and magnetic characteristics are different for the cubic and spheroid shaped nanoparticles. The iron-platinum nanoparticles have been coated by a silicon-dioxide network using a silanization reaction developed from the Stober process. Magnetic characteristics and compositional analysis of the coated iron-platinum nanoparticles were performed again using both MRI and ICP-MS. The surface of the silicon-dioxide coated ironplatinum nanoparticles was functionalized using 3-chloropropyltrimethoxy silane. The chlorine functional groups were then replaced with an azide followed by a click reaction to produce beta-cyclodextrin functionalized silica coated iron-platinum nanoparticle. An inclusion study was performed to analyze the beta-cyclodextrin functionalization reactions. These nanoparticles systems have great potential as cancer therapeutic and diagnostic agents.

scholarly journals Multiband Open-Ended Resonant Antenna Based on One ECRLH Unit Cell Structure

2017 ◽  
Vol 16 ◽  
pp. 1273-1276 ◽  
Author(s):  
Xiang Gao ◽  
Timothy James Jackson ◽  
Peter Gardner
Keyword(s):  
Cell Structure ◽  
Unit Cell ◽  
Unit Cell Structure
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