scholarly journals A TISSUE CULTURE APPROACH FOR DEVELOPING TETRAPLOID WATERMELONS

HortScience ◽  
1996 ◽  
Vol 31 (5) ◽  
pp. 747b-747
Author(s):  
Xingping Zhang ◽  
Billy B. Rhodes
Keyword(s):  
Tissue Culture ◽  
High Frequency ◽  
Shoot Organogenesis ◽  
Leaf Shape ◽  
Low Frequency ◽  
Female Fertility ◽  
Leaf Margin ◽  
The Past ◽  
Colchicine Solution ◽  
Seed Characteristics

Tetraploids are needed to synthesize triploid watermelons, which produce “seedless” fruit with improved quality. Traditionally, the tetraploids are induced by applying colchicine to the growing apex of seedlings or soaking the seeds with colchicine solution. This method often produces low frequency of tetraploids and high frequency of chimeras. Breeding tetraploids takes much longer time than breeding diploids because of the low female fertility. We developed a tissue culture approach that allows breeders to develop desirable tetraploids with commercially acceptable volume of seed in 2 years. This tissue culture approach includes: 1) regenerate plants via shoot organogenesis from cotyledon tissue; 2) screen tetraploids based on leaf morphology (more serrated leaf margin and wider leaf shape) before transplanting, and confirm tetraploids based on pollen morphology (larger pollen with four copi) and/or seed characteristics; 3) self-pollinate tetraploids or cross the tetraploids with diploids to accurately estimate the female fertility; 4) micropropagate the best tetraploid(s) using axillary buds during the off-season; and 5) produce tetraploid seed from the cloned tetraploids in an isolation plot and evaluate the triploids derived from the tetraploid(s) in the following season. This approach has been practiced on more than 20 genotypes over the past 4 years.

Fundamental properties of surface waves in lossless stratified structures

2010 ◽  
Vol 466 (2120) ◽  
pp. 2447-2469 ◽  
Author(s):  
Guido Valerio ◽  
David R. Jackson ◽  
Alessandro Galli
Keyword(s):  
Surface Waves ◽  
Dispersion Equation ◽  
High Frequency ◽  
Low Frequency ◽  
Layered Structures ◽  
Graphical Solution ◽  
Fundamental Properties ◽  
The Past ◽  
Permittivity And Permeability ◽  
Constitutive Parameters

This paper is focused on dispersive properties of lossless planar layered structures with media having positive constitutive parameters (permittivity and permeability), possibly uniaxially anisotropic. Some of these properties have been derived in the past with reference to specific simple layered structures, and are here established with more general proofs, valid for arbitrary layered structures with positive parameters. As a first step, a simple application of the Smith chart to the relevant dispersion equation is used to prove that evanescent (or plasmonic-type) waves cannot be supported by layers with positive parameters. The main part of the paper is then focused on a generalization of a common graphical solution of the dispersion equation, in order to derive some general properties about the behaviour of the wavenumbers of surface waves as a function of frequency. The wavenumbers normalized with respect to frequency are shown to be always increasing with frequency, and at high frequency they tend to the highest refractive index in the layers. Moreover, two surface waves with the same polarization cannot have the same wavenumber at a given frequency. The low-frequency behaviours are also briefly addressed. The results are derived by means of a suitable application of Foster’s theorem.

The spatio-temporal characteristics of forest fires in China: observations from hybrid remote sensing data

2020 ◽  
Author(s):  
Lei Fang ◽  
Zeyu Qiao ◽  
Jian Yang
Keyword(s):  
Forest Fire ◽  
Forest Fires ◽  
High Frequency ◽  
Fire Management ◽  
Hot Spot ◽  
Landsat Imagery ◽  
Low Frequency ◽  
Burned Area ◽  
Prevention Policy ◽  
The Past

<p>Forest fire is a natural disaster threatening global human well-beings as well as a crucial disturbance agent driving forest landscape changes. The remotely sensed burned area (BA) products can provide spatially and temporally continuous monitoring of global fires, but the accuracies remain to be improved. We firstly developed a hybrid burned area mapping approach, which integrated the advantages of a 250 m global BA product (CCI_Fire) and a 30 m global forest change (GFC) product, to generate an improved 250 m BA product (so-called CCI_GFC product). Based on 248 fire patches derived from Landsat imagery, the results showed that the CCI_GFC product improved the CCI_Fire product substantially, which are significantly better than MCD64A1 product. According to the CCI_GFC, we found the total BA in the past 17 years was about 12.1 million ha in China, which approximately covered 6.1% of the total forested areas with a significantly decreased trend through Mann-Kendall test (Tau= -0.47, P<0.05) . We conducted a grid analysis (0.05°×0.05°) to determine the hot spots of forest fire from 2001 to 2017. We also quantified fire characteristics on frequency, spatial distribution, and seasonality in terms of Burned Forest Rate (BFR), hot spot areas, and fire seasons, respectively. We found that low frequency burns with a 0<BFR≤20% in 17 years covered 64% of total grids; the medium-low frequency burns (20%<BFR≤40%), the medium frequency burns (40%<BFR≤60%), the medium-high frequency burns (60%< BFR≤80%) accounted for 15%, 7%, 4% respectively; the high frequency burns (80%<BFR≤100%) and extremely high burns (100%<BFR≤120%) together occupy 10% of total grids which mainly distributed in Xiao Hinggan mountains, south China, and southwest China. The seasonality of forest fires differed substantially among eco-regions. The fire seasons of two temperate forest eco-regions are spring and autumn. The two peak fire months are May and October, in which about 22% and 37% of the total burned area were founded respectively. As a comparison, fire seasons in tropical and subtropical eco-regions are spring and winter (i.e., November to March of the next year), which accounted 88% of the total burned area. Our study clearly illustrated the characteristics of forest fire patterns in the past 17 years, which highlighted the remarkable achievements due to a nationwide implementation of fire prevention policy. At the same time, we emphasized that it is critically important to regard the long-term forest fire dynamics to design scientific and reasonable strategies or methods for fire management and controlling, which will be of sound significance to optimize the allocation of financial resources on fire management, and to achieve sustainable management of forests.</p>

scholarly journals The Influence of Word Retrieval and Planning on Phonetic Variation: Implications for Exemplar Models

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Angela Fink ◽  
Matthew Goldrick
Keyword(s):  
High Frequency ◽  
Empirical Studies ◽  
Low Frequency ◽  
Word Retrieval ◽  
Phonetic Variation ◽  
Exemplar Models ◽  
The Past ◽  
Single Mechanism ◽  
High Frequency Words

AbstractOver the past several decades, an increasing number of empirical studies have documented the interaction of information across the traditional linguistic modules of phonetics, phonology, and lexicon. For example, the frequency with which a word occurs influences its phonetic properties of its sounds; high frequency words tend to be reduced relative to low frequency words. Lexicalist Exemplar Models have been successful in accounting for this body of results through a single mechanism,

scholarly journals The UTR-2 Very Low Frequency Sky Survey and Its Main Results

1998 ◽  
Vol 179 ◽  
pp. 100-102
Author(s):  
K.P. Sokolov
Keyword(s):  
High Frequency ◽  
Surface Brightness ◽  
Low Frequency ◽  
Source Population ◽  
Low Frequencies ◽  
Physical Conditions ◽  
The Past ◽  
Sky Survey ◽  
Low Surface Brightness ◽  
Compact Sources

During the past decade there has been a dramatic increase in the amount of high-frequency (v > 1000 MHz) data currently underlying the studies of bright compact sources (Tb ∼ 1011–12K, l ≤ 1 kpc) with flat spectra. But in order to determine physical conditions inside extragalactic radio sources at different stages of their evolution the studies of old extended (l ∼ 100 kpc) sources with low surface brightness and steep spectra which constitute the dominant radio source population at very low frequencies (v ≪ 100 MHz) are also needed. These sources are known to represent the final stage in the evolution of extragalactic objects.

scholarly journals The Generation of ULF/ELF/VLF Waves in the Ionosphere by Modulated Heating

Universe ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 29
Author(s):  
Zhe Guo ◽  
Hanxian Fang ◽  
Farideh Honary
Keyword(s):  
High Frequency ◽  
Modulation Frequency ◽  
Source Region ◽  
Low Frequency ◽  
Future Research ◽  
Very Low Frequency ◽  
The Past ◽  
Ionospheric Modification ◽  
Vlf Waves ◽  
Scientific Achievements

One of the most important effects of ionospheric modification by high power, high frequency (HF) waves is the generation of ultra low frequency/extremely low frequency/very low frequency (ULF/ELF/VLF) waves by modulated heating. This paper reviews the scientific achievements of the past five decades regarding the main mechanisms of excitation of ULF/ELF/VLF waves and discusses their characteristics, such as their electrojet dependency, the location of the source region, continuous and discontinuous waves, the number of HF arrays, and the suitable range of the modulation frequency for different proposed mechanisms. Finally, the outlook for future research in this area is presented.

scholarly journals Effect of flavour manipulation on low and high-frequency waterpipe users’ puff topography, toxicant exposures and subjective experiences

2019 ◽  
Vol 29 (Suppl 2) ◽  
pp. s95-s101 ◽  
Author(s):  
Wasim Maziak ◽  
Ziyad Ben Taleb ◽  
Mohammad Ebrahimi Kalan ◽  
Melissa Ward-Peterson ◽  
Zoran Bursac ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Subjective Experiences ◽  
Toxicant Exposure ◽  
The Past ◽  
Plasma Nicotine ◽  
The Usa ◽  
Ad Libitum ◽  
Major Factors ◽  
The Impact

BackgroundFlavoured tobacco is one of the major factors behind the popularity of waterpipe (WP) smoking in the USA and internationally. The current study examined the impact of flavour manipulation on satisfaction, puff topography and toxicant exposure among high-frequency and low-frequency WP users.MethodThis cross-over study was conducted among 144 current (past month) WP smokers reporting WP smoking less than once a week (low-frequency users; n=69) or at least once a week (high-frequency users; n=75) in the past 6 months. Participants attended two counterbalanced 45 min ad libitum smoking sessions that differed by flavour (preferred flavoured vs unflavoured tobacco), preceded by ≥12 hours of tobacco use abstinence. Outcome measures included puff topography, expired carbon monoxide (eCO), plasma nicotine and subjective measures.ResultsBoth high-frequency and low-frequency WP users reported an enhanced smoking experience and greater interest in future use after smoking the flavoured compared with unflavoured tobacco (p<0.05 for all). High-frequency users, however, were more keen on smoking the flavoured tobacco in the future, had higher puffing parameters in general compared with low-frequency users (p<0.05 for all) and had no differences in eCO and plasma nicotine concentrations between the flavoured and unflavoured tobacco conditions (p>0.05 for all). On the other hand, low-frequency users had significantly greater eCO and plasma nicotine concentrations following smoking the unflavoured compared with flavoured tobacco condition (p<0.05 for all).ConclusionsOur results indicate that removing flavours will likely negatively affect WP satisfaction and future use and that such an effect will be more pronounced among high-frequency compared with low-frequency WP smokers.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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