scholarly journals Structural deformation and host–guest properties of doubly-reduced cycloparaphenylenes, [n]CPPs2− (n = 6, 8, 10, and 12)

2020 ◽  
Vol 11 (35) ◽  
pp. 9395-9401 ◽  
Author(s):  
Zheng Zhou ◽  
Zheng Wei ◽  
Tobias A. Schaub ◽  
Ramesh Jasti ◽  
Marina A. Petrukhina
Keyword(s):  
Structural Changes ◽  
Structural Deformation ◽  
Size Dependent

The series of doubly-reduced cycloparaphenylenes (CPPs) with increasing dimensions and flexibility shows the size-dependent structural changes and enhanced host abilities.

Size dependent behavior of Fe3O4crystals during electrochemical (de)lithiation: an in situ X-ray diffraction, ex situ X-ray absorption spectroscopy, transmission electron microscopy and theoretical investigation

2017 ◽  
Vol 19 (31) ◽  
pp. 20867-20880 ◽  
Author(s):  
David C. Bock ◽  
Christopher J. Pelliccione ◽  
Wei Zhang ◽  
Janis Timoshenko ◽  
K. W. Knehr ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
X Ray ◽  
Size Dependent ◽  
Transmission Electron ◽  
Dependent Behavior ◽  
X Ray Absorption

Crystal and atomic structural changes of Fe3O4upon electrochemical (de)lithiation were determined.

scholarly journals Manipulating efficient light emission in two-dimensional perovskite crystals by pressure-induced anisotropic deformation

2019 ◽  
Vol 5 (7) ◽  
pp. eaav9445 ◽  
Author(s):  
Sheng Liu ◽  
Shishuai Sun ◽  
Chee Kwan Gan ◽  
Andrés Granados del Águila ◽  
Yanan Fang ◽  
...  
Keyword(s):  
Structural Changes ◽  
Light Emission ◽  
Driving Forces ◽  
Quantum Confinement Effect ◽  
Visible Spectrum ◽  
Structural Deformation ◽  
Moderate Pressure ◽  
Two Dimensional ◽  
New Paradigm ◽  
Lead Iodide

The hybrid nature and soft lattice of organolead halide perovskites render their structural changes and optical properties susceptible to external driving forces such as temperature and pressure, remarkably different from conventional semiconductors. Here, we investigate the pressure-induced optical response of a typical two-dimensional perovskite crystal, phenylethylamine lead iodide. At a moderate pressure within 3.5 GPa, its photoluminescence red-shifts continuously, exhibiting an ultrabroad energy tunability range up to 320 meV in the visible spectrum, with quantum yield remaining nearly constant. First-principles calculations suggest that an out-of-plane quasi-uniaxial compression occurs under a hydrostatic pressure, while the energy is absorbed by the reversible and elastic tilting of the benzene rings within the long-chain ligands. This anisotropic structural deformation effectively modulates the quantum confinement effect by 250 meV via barrier height lowering. The broad tunability within a relatively low pressure range will expand optoelectronic applications to a new paradigm with pressure as a tuning knob.

Investigation of Local Structures Around Luminescent Centers in Doped Nanocrystal Phosphors

1995 ◽  
Vol 405 ◽  
Author(s):  
Y. L. Soo ◽  
S. W. Huang ◽  
Z. H. Ming ◽  
Y. H. Kao ◽  
E. Goldburt ◽  
...  
Keyword(s):  
Optical Properties ◽  
Structural Changes ◽  
Structural Information ◽  
The Novel ◽  
X Ray ◽  
Local Structures ◽  
Size Dependent ◽  
Luminescent Centers ◽  
X Ray Absorption ◽  
Mn Doped

AbstractExtended x-ray absorption fine structure (EXAFS) technique has been employed to investigate the local structures around luminescent centers in nanocrystals of Mn-doped ZnS and Tb-doped Y2O3. Size-dependent local structural changes around Mn luminescent centers have been found in Mn-doped nanocrystals of ZnS by using Mn K-edge EXAFS. Local structures around Tb investigated by Tb Li-edge EXAFS also show substantial differences between bulk and nanocrystal samples. This structural information is useful for understanding the novel optical properties of doped nanocrystals.

scholarly journals Development of Eye Phantoms for Mimicking the Structural Deformation of the Human Cornea Accompanied With Intraocular Pressure Alteration

2021 ◽  
Author(s):  
Han Saem Cho ◽  
Sae Chae Jeoung
Keyword(s):  
Intraocular Pressure ◽  
Structural Changes ◽  
Corneal Thickness ◽  
Structural Deformation ◽  
Accurate Estimation ◽  
Radius Of Curvature ◽  
Human Cornea ◽  
Different Types ◽  
Corneal Radius

Abstract We developed a fully continuous eye phantom to better understand structural deformation of the cornea under varying intraocular pressure (IOP). The IOP-induced deformation and tension of the eye phantom were investigated using optical coherence tomography and non-contact tonometer readings, respectively. A fixed-cornea eye phantom, which featured a soft cornea, was also used for comparison. We evaluated the corneal structural changes between the two different types of eye phantoms by estimating the central corneal thickness (CCT) and corneal radius of curvature (CRC). For the eye phantom with an initial CCT of 0.55 mm, which is close to the average human CCT, CRC of the fully continuous eye phantoms showed a positive correlation to true IOP, while the CRC of a fixed-cornea eye phantom had a negative correlation. Non-contact tonometry readings for fixed-cornea eye phantoms were higher than those of full-eye phantoms due to the structural and mechanical characteristics. Considering the results from in vitro studies on enucleated human eyeballs, a fully continuous eye phantom is a more suitable choice for mimicking human IOP than a fixed-cornea eye phantom. Use of a more reliable eye phantom for accurate estimation of IOP using tonometry may eventually improve the accuracy of glaucoma screening.

scholarly journals Size-Dependent Structural Properties of a High-Nb TiAl Alloy Powder

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 161 ◽  
Author(s):  
Binglin Liu ◽  
Maosong Wang ◽  
Yulei Du ◽  
Jingxiao Li
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Structural Properties ◽  
Structural Changes ◽  
Structural Characteristics ◽  
Nominal Composition ◽  
Induction Melting ◽  
Powder Size ◽  
Size Dependent ◽  
High Temperature Xrd

TiAl-based alloys are promising light weight structural materials for high temperature applications in the field of aerospace. Recently, fabrication technologies starting from powders including powder metallurgy and additive manufacturing have been developed to overcome the difficulties in the processing, machining and shaping of TiAl-based alloys. Spherical alloy powders with different particle size distributions are usually used in these fabrication techniques. The purpose of this study is to reveal the size-dependent structural properties of a high-Nb TiAl powder for these fabrication technologies starting from powders. A high-Nb TiAl pre-alloyed powder with nominal composition of Ti-48Al-2Cr-8Nb (at. %) was prepared by the electrode induction melting gas atomization (EIGA) method. The phase structure and morphology of the as-atomized powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The size-dependent structural changes of the as-atomized powders with different sizes were studied by differential scanning calorimetry (DSC) and in situ high temperature XRD. It was found that with decreasing the powder size, the content of the γ-TiAl phase decreases and the α2-Ti3Al phase increases. The α2-Ti3Al to γ-TiAl phase transformation was found in the temperature range of 600–770 °C. Based on the present work, the structural characteristics of TiAl powders are strongly dependent on their particle size, which should be considered in optimizing the process parameters of TiAl alloys fabricated from powders.

Size Dependent Structural, Vibrational, and Luminescence Properties of Nanocrystalline LiIn(WO4)2:Cr3+

2008 ◽  
Vol 8 (7) ◽  
pp. 3545-3554 ◽  
Author(s):  
K. Hermanowicz ◽  
M. Maczka ◽  
P. E. Tomaszewski ◽  
L. Krajczyk ◽  
J. Hanuza ◽  
...  
Keyword(s):  
Particle Size ◽  
Structural Changes ◽  
Pechini Method ◽  
Phonon Coupling ◽  
Covalent Character ◽  
X Ray ◽  
Electron Transmission ◽  
Size Dependent ◽  
Electron Phonon Coupling ◽  
Critical Particle Size

X-ray, electron transmission spectroscopy, vibrational and luminescence studies of LiIn(WO4)2:Cr3+ nanoparticles prepared by Pechini method are reported. On annealing the sample several structural changes were observed resulting in a creation of three new, previously unknown polymorphs. It was shown that this tungstate undergoes two size-induced phase transitions from the structure similar to LiFe(WO4)2 into the structure similar to LiYb(WO4)2 and then into the structure of LiGa(WO4)2 type. These transitions occur for the critical particle size of about 100 and 30 nm, and they could be attributed mainly to some changes in the distribution of the sites occupied by Li+ and In3+ ions. Luminescence studies revealed decrease of the covalent character of chromium environment and electron–phonon coupling strength with decreasing size of the nanoparticles.

scholarly journals Monitoring of Biological Changes in Electromechanical Reshaping of Cartilage Using Imaging Modalities

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Seok Jin Hong ◽  
Minseok Lee ◽  
Connie J. Oh ◽  
Sehwan Kim
Keyword(s):  
Minimally Invasive ◽  
Structural Changes ◽  
Thermal Damage ◽  
Imaging Modality ◽  
Local Stress ◽  
Imaging Modalities ◽  
Structural Deformation ◽  
Electrochemical Mechanism ◽  
Tissue Matrix ◽  
Cartilage Reshaping

Electromechanical reshaping (EMR) is a promising surgical technique used to reshape cartilage by direct current and mechanical deformation. It causes local stress relaxation and permanent alterations in the shape of cartilage. The major advantages of EMR are its minimally invasive nature and nonthermal electrochemical mechanism of action. The purpose of this study is to validate that EMR does not cause thermal damage and to observe structural changes in post-EMR cartilage using several imaging modalities. Three imaging modality metrics were used to validate the performance of EMR by identifying structural deformation during cartilage reshaping: infrared thermography was used to sense the temperature of the flat cartilages (16.7°C at 6 V), optical coherence tomography (OCT) was used to examine the change in the cartilage by gauging deformation in the tissue matrix during EMR, and scanning electron microscopy (SEM) was used to show that EMR-treated cartilage is irregularly arranged and the thickness of collagen fibers varies, which affects the change in shape of the cartilage. In conclusion, the three imaging modalities reveal the nonthermal and electromechanical mechanisms of EMR and demonstrate that use of an EMR device is feasible for reshaping cartilage in a minimally invasive manner.

Fine Structural Changes in the Microvasculature of the Mouse Pinna: Aging and Radiation Injury

1974 ◽  
Vol 32 ◽  
pp. 54-55
Author(s):  
S. Phyllis Steamer ◽  
Rosemarie L. Devine
Keyword(s):  
Structural Changes ◽  
Radiation Treatment ◽  
Arterial Stenosis ◽  
Ultrastructural Changes ◽  
Vascular Effects ◽  
Microvascular Changes ◽  
Surrounding Connective Tissue ◽  
Fission Neutrons ◽  
Total Body

The importance of radiation damage to the skin and its vasculature was recognized by the early radiologists. In more recent studies, vascular effects were shown to involve the endothelium as well as the surrounding connective tissue. Microvascular changes in the mouse pinna were studied in vivo and recorded photographically over a period of 12-18 months. Radiation treatment at 110 days of age was total body exposure to either 240 rad fission neutrons or 855 rad 60Co gamma rays. After in vivo observations in control and irradiated mice, animals were sacrificed for examination of changes in vascular fine structure. Vessels were selected from regions of specific interest that had been identified on photomicrographs. Prominent ultrastructural changes can be attributed to aging as well as to radiation treatment. Of principal concern were determinations of ultrastructural changes associated with venous dilatations, segmental arterial stenosis and tortuosities of both veins and arteries, effects that had been identified on the basis of light microscopic observations. Tortuosities and irregularly dilated vein segments were related to both aging and radiation changes but arterial stenosis was observed only in irradiated animals.

Production and STEM examination of controlled-size silver clusters

1983 ◽  
Vol 41 ◽  
pp. 338-339
Author(s):  
M. A. Listvan ◽  
R. P. Andres
Keyword(s):  
Cluster Size ◽  
Metal Clusters ◽  
Experimental Parameter ◽  
Carbon Films ◽  
Metal Species ◽  
Silver Clusters ◽  
Free Jet ◽  
Size Dependent ◽  
Cluster Properties ◽  
Controllable Size

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

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