Effects of temperature and comonomer content on poly(ε-Caprolactam-Co-ε-Caprolactone) copolymers properties: An evaluation of structural changes and dielectric behavior

2018 ◽  
Vol 59 (3) ◽  
pp. 465-477 ◽  
Author(s):  
Elena Rusu ◽  
Gh. Rusu ◽  
D. Rusu
Keyword(s):  
Structural Changes ◽  
Dielectric Behavior ◽  
Effects Of Temperature ◽  
Comonomer Content

Tuning the Electric Field Response of MOFs by Rotatable Dipolar Linkers

2019 ◽  
Author(s):  
Johannes P. Dürholt ◽  
Babak Farhadi Jahromi ◽  
Rochus Schmid
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Structural Changes ◽  
Dielectric Behavior ◽  
Two Dimensions ◽  
Dielectric Constants ◽  
Electric Response ◽  
Dipole Strength ◽  
Metal Organic ◽  
Dynamics Simulations

Recently the possibility of using electric fields as a further stimulus to trigger structural changes in metal-organic frameworks (MOFs) has been investigated. In general, rotatable groups or other types of mechanical motion can be driven by electric fields. In this study we demonstrate how the electric response of MOFs can be tuned by adding rotatable dipolar linkers, generating a material that exhibits paralectric behavior in two dimensions and dielectric behavior in one dimension. The suitability of four different methods to compute the relative permittivity κ by means of molecular dynamics simulations was validated. The dependency of the permittivity on temperature T and dipole strength μ was determined. It was found that the herein investigated systems exhibit a high degree of tunability and substantially larger dielectric constants as expected for MOFs in general. The temperature dependency of κ obeys the Curie-Weiss law. In addition, the influence of dipolar linkers on the electric field induced breathing behavior was investigated. With increasing dipole moment, lower field strength are required to trigger the contraction. These investigations set the stage for an application of such systems as dielectric sensors, order-disorder ferroelectrics or any scenario where movable dipolar fragments respond to external electric fields.

Tuning the Electric Field Response of MOFs by Rotatable Dipolar Linkers

2019 ◽  
Author(s):  
Johannes P. Dürholt ◽  
Babak Farhadi Jahromi ◽  
Rochus Schmid
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Structural Changes ◽  
Dielectric Behavior ◽  
Two Dimensions ◽  
Dielectric Constants ◽  
Electric Response ◽  
Dipole Strength ◽  
Metal Organic ◽  
Dynamics Simulations

Recently the possibility of using electric fields as a further stimulus to trigger structural changes in metal-organic frameworks (MOFs) has been investigated. In general, rotatable groups or other types of mechanical motion can be driven by electric fields. In this study we demonstrate how the electric response of MOFs can be tuned by adding rotatable dipolar linkers, generating a material that exhibits paralectric behavior in two dimensions and dielectric behavior in one dimension. The suitability of four different methods to compute the relative permittivity κ by means of molecular dynamics simulations was validated. The dependency of the permittivity on temperature T and dipole strength μ was determined. It was found that the herein investigated systems exhibit a high degree of tunability and substantially larger dielectric constants as expected for MOFs in general. The temperature dependency of κ obeys the Curie-Weiss law. In addition, the influence of dipolar linkers on the electric field induced breathing behavior was investigated. With increasing dipole moment, lower field strength are required to trigger the contraction. These investigations set the stage for an application of such systems as dielectric sensors, order-disorder ferroelectrics or any scenario where movable dipolar fragments respond to external electric fields.

STRUCTURAL AND PIEZOELECTRIC PROPERTIES OF (1 − x)PZT-xBFN (x = 0.1 – 0.2) SOLID SOLUTION

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4724-4729
Author(s):  
KRIT SUTJARITTANGTHAM ◽  
SUKUM EITSSAYEAM ◽  
KAMONPAN PENGPAT ◽  
GOBWUTE RUJIJANAGUL ◽  
TAWEE TUNKASIRI ◽  
...  
Keyword(s):  
Structural Changes ◽  
Piezoelectric Properties ◽  
Measurement Techniques ◽  
Xrd Analysis ◽  
Dielectric Behavior ◽  
Phase Changes ◽  
Dielectric Measurement ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Piezoelectric Measurement

The structural, dielectric and piezoelectric properties of (1 − x) PbZr 0.52 Ti 0.48 O 3– xBaFe 0.5 Nb 0.5 O 3 ceramic system with the composition near the morphotropic phase boundary were investigated as a function of the BaFe 0.5 Nb 0.5 O 3 content by X-ray diffraction (XRD), dielectric measurement and piezoelectric measurement techniques. Studies were performed on the samples prepared by solid state reaction for x = 0.10, 0.12, 0.14, 0.16, 0.18 and 0.20. The XRD analysis demonstrated that with increasing BFN content in (1 − x) PZT −x BFN , the structural change occurred from tetragonal to the mixture of tetragonal and cubic phase. Changes in the dielectric behavior and piezoelectric properties were found to relate with these structural changes depending on the BFN contents.

scholarly journals Correlations between structural changes and dielectric behavior of thermally aged XLPE

2019 ◽  
Vol 26 (6) ◽  
pp. 1859-1866 ◽  
Author(s):  
Youcef Kemari ◽  
Abdelouahab Mekhaldi ◽  
Gilbert Teyssedre ◽  
Madjid Teguar
Keyword(s):  
Structural Changes ◽  
Dielectric Behavior

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.

Evaluation of single-electron movies of glutamine synthetase molecules

1983 ◽  
Vol 41 ◽  
pp. 280-281
Author(s):  
W. Kunath ◽  
E. Zeitler ◽  
M. Kessel
Keyword(s):  
Electron Microscope ◽  
Glutamine Synthetase ◽  
Electron Irradiation ◽  
Structural Damage ◽  
Structural Changes ◽  
Single Electron ◽  
Continuous Series ◽  
Digital Recording ◽  
Recording Device ◽  
Low Exposure

The features of digital recording of a continuous series (movie) of singleelectron TV frames are reported. The technique is used to investigate structural changes in negatively stained glutamine synthetase molecules (GS) during electron irradiation and, as an ultimate goal, to look for the molecules' “undamaged” structure, say, after a 1 e/Å2 dose.The TV frame of fig. la shows an image of 5 glutamine synthetase molecules exposed to 1/150 e/Å2. Every single electron is recorded as a unit signal in a 256 ×256 field. The extremely low exposure of a single TV frame as dictated by the single-electron recording device including the electron microscope requires accumulation of 150 TV frames into one frame (fig. lb) thus achieving a reasonable compromise between the conflicting aspects of exposure time per frame of 3 sec. vs. object drift of less than 1 Å, and exposure per frame of 1 e/Å2 vs. rate of structural damage.

Fine Structural Changes in the Adenohypophyses of Rats Following Destruction of the Pituitary Stalk

1977 ◽  
Vol 35 ◽  
pp. 496-497
Author(s):  
K. Kovacs ◽  
E. Horvath ◽  
J. M. Bilbao ◽  
F. A. Laszlo ◽  
I. Domokos
Keyword(s):  
Structural Changes ◽  
Tissue Injury ◽  
Anterior Lobe ◽  
Uranyl Acetate ◽  
Male Rats ◽  
Pituitary Stalk ◽  
Sequence Of Events ◽  
Pituitary Glands ◽  
Electrolytic Lesions ◽  
Ultrathin Sections

Electrolytic lesions of the pituitary stalk in rats interrupt adenohypophysial blood flow and result in massive infarction of the anterior lobe. In order to obtain a deeper insight into the morphogenesis of tissue injury and to reveal the sequence of events, a fine structural investigation was undertaken on adenohypophyses of rats at various intervals following destruction of the pituitary stalk.The pituitary stalk was destroyed electrolytically, with a Horsley-Clarke apparatus on 27 male rats of the R-Amsterdam strain, weighing 180-200 g. Thirty minutes, 1,2,4,6 and 24 hours after surgery the animals were perfused with a glutaraldehyde-formalin solution. The skulls were then opened and the pituitary glands removed. The anterior lobes were fixed in glutaraldehyde-formalin solution, postfixed in osmium tetroxide and embedded in Durcupan. Ultrathin sections were stained with uranyl acetate and lead citrate and investigated with a Philips 300 electron microscope.

Membrane Changes in Polymorphonuclear Leukocytes During Ionophore (A23187) - Induced Lysosomal Release

1977 ◽  
Vol 35 ◽  
pp. 482-483
Author(s):  
P.L. Moore ◽  
P.L. Sannes ◽  
H.L. Bank ◽  
S.S. Spicer
Keyword(s):  
Structural Changes ◽  
Calcium Release ◽  
Clear Understanding ◽  
Ionophore A23187 ◽  
Enzyme Release ◽  
Extracellular Medium ◽  
Pmn Leukocytes ◽  
Intracellular Ion Concentrations ◽  
Membrane Changes ◽  
Pmn Leukocyte

It is thought that calcium and/or magnesium may play important roles in polymorphonuclear (PMN) leukocyte functions such as chemotaxis, adhesion and phagocytosis. Yet, a clear understanding of the biological roles of these ions has awaited the development of techniques which permit a selective alteration of intracellular ion concentrations. Recently, treatment of cells with the ionophore A23187 has been used to alter intracellular divalent cation concentrations. This ionophore is a lipid soluble antibiotic produced by Streptomyces chartreusensis that complexes with both calcium and magnesium (3) and is believed to carry these ions across biological membranes (4). Biochemical investigations of human PMN leukocytes demonstrate that cells treated with A23187 and extracellular calcium release their lysosomal enzymes into the extracellular medium without rupturing and releasing their soluble cytoplasmic enzymes (5,6). The aim of the present study and and a companion report (7) was to investigate the structural changes that occur in leukocytes during ionophore-induced lysosomal enzyme release.

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