scholarly journals Communication—Tunable Negative Permittivity of Cobalt and Epoxy Composites at 3 kHz ~ 1 MHz Frequency Regions

2021 ◽  
Author(s):  
Min Chen ◽  
Kai Sun ◽  
Xuai Wang ◽  
Yanmin Wang
Keyword(s):  
Potential Application ◽  
Low Frequency ◽  
Negative Permittivity ◽  
Epoxy Composites ◽  
Conductive Network ◽  
Free Electrons ◽  
Metal Composites ◽  
Large Numbers

Abstract Negative permittivity in percolation composites has drawn much attention owing to their potential application. This study set out to explore whether tunable negative permittivity can be realized in metal composites at 3 kHz ~ 1 MHz frequency regions. When the content of cobalt is 80 wt%, the permittivity turns to negative in the test band. These findings show that the Co conductive network has formed and provides large numbers of free electrons. Meanwhile, the percolation composites with negative permittivity show inductive characteristic. This research supports the idea that tunable low-frequency negative permittivity can be realized in metal composites.

Negative Permittivity Behavior in Silver/Polyaniline Metacomposites Induced by the Low-Frequency Plasmonic Oscillation

2021 ◽  
Author(s):  
Jiahong Tian ◽  
Runhua Fan ◽  
Zongxiang Wang ◽  
Jiahao Xin ◽  
Zhongyang Wang
Keyword(s):  
Synthesis Method ◽  
Low Frequency ◽  
In Situ Synthesis ◽  
Negative Permittivity ◽  
Free Electrons ◽  
Dominant Effect ◽  
Equivalent Circuit Analysis ◽  
Inductive Character ◽  
Percolation Network

Abstract Silver/polyaniline (Ag/PANI) composites were prepared by an in-situ synthesis method. Interestingly, the permittivity changed from positive to negative along with the formation of percolation network. The plasma oscillations of free electrons from the network made a dominant effect on the negative permittivity behavior. Further investigation based on equivalent circuit analysis revealed that the composites with negative permittivity presented inductive character. The epsilon-negative composites can be applied to electromagnetic shielding, absorbing and attenuation.

Tailorable epsilon-negative and epsilon-near-zero behavior of TiC/CCTO metacomposites: Low-frequency plasma oscillation

2021 ◽  
pp. 2150015
Author(s):  
Baogang Ding ◽  
Yunpeng Qu ◽  
Kai Sun ◽  
Runhua Fan
Keyword(s):  
Plasma Oscillation ◽  
Three Dimensional ◽  
Low Frequency ◽  
Calcium Titanate ◽  
Negative Permittivity ◽  
Free Electrons ◽  
Frequency Plasma ◽  
Collective Plasma ◽  
Negative Formula ◽  
Epsilon Near Zero

Epsilon-negative ([Formula: see text]) and epsilon-near-zero (ENZ) property was demonstrated in titanium carbide/copper calcium titanate (TiC/CCTO) metacomposites. Benefiting from the moderate concentration of free electrons in TiC filler and its adjustable three-dimensional (3D) networks, weakly negative permittivity ([Formula: see text]200 at 20 MHz) was achieved. Not only that, tailoring the negative permittivity of metacomposites from [Formula: see text]200 to [Formula: see text]2060, [Formula: see text]4200, [Formula: see text]14000 and [Formula: see text]70000 at 20 MHz was realized by simply increasing TiC content. Besides, Drude model was used to explain the radio-frequency (RF) negative permittivity and quantified the collective plasma oscillation in TiC networks.

scholarly journals A TEST FOR RARE MALE MATING ADVANTAGE WITH DROSOPHILA PSEUDOOBSCURA KARYOTYPES

Genetics ◽  
1984 ◽  
Vol 107 (4) ◽  
pp. 577-589
Author(s):  
Wyatt W Anderson ◽  
Celeste J Brown
Keyword(s):  
Mating Success ◽  
Low Frequency ◽  
Behavioral Observation ◽  
Drosophila Pseudoobscura ◽  
Male Mating ◽  
Frequency Dependent ◽  
Mating Advantage ◽  
Large Numbers ◽  
Laboratory Populations ◽  
Statistical Artifact

ABSTRACT Recent work has called into question the reality of the rare male mating advantage, pointing out that it could be a statistical artifact of marking flies for behavioral observation or of experimental bias in collecting males. We designed an experiment to test for rare male mating advantage that avoids these sources of bias. Large numbers of males of three Drosophila pseudoobscura karyotypes were allowed to mate with females of one karyotype in population cages. The females were then isolated before multiple mating occurred and their progeny used to diagnose the males that mated them. Populations were studied at five sets of male karyotypic frequencies. The mating success of the male homokaryotypes ST/ST and CH/CH, relative to that of the heterokaryotype ST/CH, was frequency dependent. Both ST/ST and CH/CH males displayed a statistically significant mating advantage at low frequency by comparision with their mating success in the midrange of karyotypic frequencies. Both male homokaryotypes also showed a significantly greater mating success at high homokaryotypic frequency than at intermediate frequencies, which is the same as saying that the heterokaryotype not only failed to show a rare male advantage but actually suffered a mating disadvantage at low frequency. We conclude that rare male mating advantage is not always an experimental or methodological artifact but does occur in laboratory populations of D. pseudoobscura. It may occur for some genotypes and not for others, however, and it may be only one of several forms of frequency-dependent mating behavior operating in a population.

scholarly journals Two families of elliptical plasma lenses

2019 ◽  
Vol 488 (4) ◽  
pp. 5651-5664 ◽  
Author(s):  
Xinzhong Er ◽  
Adam Rogers
Keyword(s):  
Parameter Space ◽  
Gravitational Lensing ◽  
Low Frequency ◽  
Wavelength Dependence ◽  
Free Electrons ◽  
Density Distributions ◽  
Critical Curves ◽  
Numerical Studies ◽  
Plasma Distribution ◽  
Elliptical Plasma

ABSTRACT Plasma lensing is the refraction of low-frequency electromagnetic rays due to free electrons in the interstellar medium. Although the phenomenon has a distinct similarity to gravitational lensing, particularly in its mathematical description, plasma lensing introduces other additional features, such as wavelength dependence, radial rather than tangential image distortions, and strong demagnification of background sources. Axisymmetrical models of plasma lenses have been well studied in the literature, but density distributions with more complicated shapes can provide new and exotic image configurations and increase the richness of the magnification properties. As a first step towards non-axisymmetrical distributions, we study two families of elliptical plasma lens, softened power law, and exponential plasma distributions. We perform numerical studies on each lens model, and present them over a parameter space. In addition to deriving elliptical plasma lens formulae, we also investigate the number of critical curves that the lens can produce by studying the lens parameter space, in particular the dependence on the lensing ellipticity. We find that the introduction of ellipticity into the plasma distribution can enhance the lensing effects as well as the complexity of the magnification map.

Low-frequency plasmonic state and negative permittivity in copper/titanium dioxide percolating composites

2021 ◽  
Vol 47 (2) ◽  
pp. 2208-2213
Author(s):  
Zaixin Wei ◽  
Zhongyang Wang ◽  
Guohua Fan ◽  
Ciqun Xu ◽  
Guangyue Shi ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Low Frequency ◽  
Negative Permittivity

scholarly journals Potentialities of a Laser-Induced Breakdown Spectroscopy Technique in the Study of Polymer Composites

2020 ◽  
Vol 74 (6) ◽  
pp. 655-660
Author(s):  
Sebastián Tognana ◽  
Cristian D'Angelo ◽  
Walter Salgueiro ◽  
Susana Montecinos
Keyword(s):  
Polymer Composites ◽  
Potential Application ◽  
Volume Fraction ◽  
Filler Content ◽  
Epoxy Composites ◽  
Laser Induced Breakdown Spectroscopy ◽  
Spectroscopy Technique ◽  
Breakdown Spectroscopy ◽  
Filler Volume Fraction ◽  
Laser Induced Breakdown

A laser-induced breakdown spectroscopy (LIBS) technique was used to evaluate the filler content in particulate epoxy–copper composites. A potential application for a direct and fast measurement of the filler in composites through the LIBS results is suggested using calibrated samples. The methodology used in this work makes possible the incorporation of LIBS as a quantitative technique for the study of particle metal-filled epoxy composites, providing a method to obtain a direct estimation of the filler volume fraction.

GENETIC STUDIES OF PIGMENTATION OF STAPHYLOCOCCUS AUREUS

1967 ◽  
Vol 13 (4) ◽  
pp. 389-395 ◽  
Author(s):  
Robert A. Altenbern
Keyword(s):  
Staphylococcus Aureus ◽  
Optical Density ◽  
Point Mutations ◽  
Low Frequency ◽  
Pigment Content ◽  
Single Site ◽  
Genetic Studies ◽  
Large Numbers ◽  
Acridine Dyes

Exposure of cells of several strains of Staphylococcus aureus to 50 or 100 μg of N-methyl-N′-nitro-N-nitrosoguanidine for 30 to 60 minutes induced large numbers of mutants with pigment content different from that of the parent. By determination of the amount of pigment as related to the optical density of the cells, four to seven classes of pigmentation mutants could be defined. Mutants with pigment content differing from that of the parent could readily be mutated to other pigmentation states and are thus probable point mutations. In contrast, completely white mutants could not be induced by the mutagen to any degree of pigmentation and possibly represent minor deletions or cumulative single-site mutations in the chromosome. Growth of parent strains in media containing acridine dyes occasionally produced a low frequency (0.01%) of white mutants. Mutants differing in pigment content from that of the parent were unable to produce coagulase during growth, although the parent cultures elaborated considerable coagulase under identical conditions.

ESTIMATING MORTALITY OF SEABIRDS FROM OIL SPILLS

1987 ◽  
Vol 1987 (1) ◽  
pp. 547-551 ◽  
Author(s):  
R. Glenn Ford ◽  
Gary W. Page ◽  
Harry R. Carter
Keyword(s):  
Real Time ◽  
Emergency Response ◽  
Oil Spill ◽  
Potential Application ◽  
Damage Assessment ◽  
Oil Spills ◽  
Central California ◽  
Marine Oil ◽  
Large Numbers ◽  
Using Data

ABSTRACT From an aesthetic and damage assessment standpoint, the loss of seabirds may be one of the more important results of a marine oil spill. Assessment of the actual numbers of seabirds killed is difficult because the bodies of dead or incapacitated seabirds are often never found or recorded. We present a computer methodology that estimates the number of birds that come in contact with an oil spill and partitions these birds among four possible fates: (1) swimming or flying ashore under their own power; (2) carried out to sea by winds and currents; (3) carried inshore, but lost before being beached; and (4) beached by winds and currents. Beached birds are further divided into those that are recovered and those that are not. The accuracy of the methodology is examined using data for two recent spills in central California, each of which resulted in the beachings of large numbers of birds. The methodology also has potential application to real-time emergency response by predicting when and where the greatest numbers of bird beachings will occur.

scholarly journals Selection of antigen-specific, idiotype-positive B cells in transgenic mice expressing a rearranged M167-mu heavy chain gene.

1991 ◽  
Vol 174 (5) ◽  
pp. 1189-1201 ◽  
Author(s):  
J J Kenny ◽  
C O'Connell ◽  
D G Sieckmann ◽  
R T Fischer ◽  
D L Longo
Keyword(s):  
Bone Marrow ◽  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Flow Cytometric Analysis ◽  
Low Frequency ◽  
Surface Expression ◽  
Chain Gene ◽  
Large Numbers ◽  
Selection Of

Flow cytometric analysis of antigen-specific, idiotype-positive (id+), B cell development in transgenic mice expressing a rearranged M167-mu gene shows that large numbers of phosphocholine (PC)-specific, M167-id+ B cells develop in the spleen and bone marrow of these mice. Random rearrangement of endogenous V kappa genes, in the absence of a subsequent receptor-driven selection, should give rise to equal numbers of T15- and M167-id+ B cells. The observed 100-500-fold amplification of M167-id+ B cells expressing an endogenous encoded V kappa 24]kappa 5 light chain in association with the M167 VH1-id transgene product appears to be an antigen driven, receptor-mediated process, since no amplification of non-PC-binding M167 VH1/V kappa 22, T15-id+ B cells occurs in these mu-only transgenic mice. The selection and amplification of antigen-specific, M167-id+ B cells requires surface expression of the mu transgene product; thus, no enhancement of M167-id+ B cells occurs in the M167 mu delta mem-transgenic mice, which cannot insert the mu transgene product into the B cell membrane. Surprisingly, no selection of PC-specific B cells occurs in M167-kappa-transgenic mice although large numbers of B cells expressing a crossreactive M167-id are present in the spleen and bone marrow of these mice. The failure to develop detectable numbers of M167-id+, PC-specific B cells in M167-kappa-transgenic mice may be due to a very low frequency of M167-VH-region formation during endogenous rearrangement of VH1 to D-JH segments. The somatic generation of the M167 version of a rearranged VH1 gene may occur in less than one of every 10(5) bone marrow B cells, and a 500-fold amplification of this M167-Id+ B cell would not be detectable by flow cytometry even though the anti-PC antibody produced by these B cells is detectable in the serum of M167-kappa-transgenic mice after immunization with PC.

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