scholarly journals Statistical analysis of radar observed F region irregularities from three longitudinal sectors

2013 ◽  
Vol 31 (12) ◽  
pp. 2137-2146 ◽  
Author(s):  
R. Y. C. Cueva ◽  
E. R. de Paula ◽  
A. E. Kherani
Keyword(s):  
Onset Time ◽  
Solar Flux ◽  
Christmas Island ◽  
F Region ◽  
Incoherent Scatter Radars ◽  
Declination Angle ◽  
Spread F ◽  
Occurrence Characteristics ◽  
Using Data

Abstract. Equatorial Spread F (ESF) is a manifestation of ionospheric interchange instabilities in the nighttime equatorial F region. These instabilities generate plasma density irregularities with scale sizes ranging from centimetres to thousands of kilometres. The irregularities can be detected from a variety of instruments such as digisonde, coherent and incoherent scatter radars, in situ space probes, and airglow photometers. In the present study, occurrence statistics of the ESF, based on various parameters are presented using data obtained from the VHF radars located at three longitudinally separated equatorial stations: Christmas Island (2° N, 202.6° E, 2.9° N dip latitude), São Luís (2.59° S, 315.8° E, 0.5° S dip latitude) and Jicamarca (12° S, 283.1° E, 0.6° N dip latitude). The ESF parameters presented here are the onset altitude, onset time (onset refers to first appearance of signal in the radar field of view) of the bottom-type and plume, and the peak altitude of the plume. Recent studies have used these parameters to classify the spread F occurrence characteristics. The present study reveals novel features namely, the dependence of ESF parameters on the seasonal, solar flux, declination angle and longitudinal dependence from the three radar sites. In addition, we also present an empirical model to determine the nature of these ESF parameters as a function of the solar flux which may enable us to forecast (with 30 min to 1 h tolerance) the plume occurrence at any longitude located in between São Luís and Christmas Island.

scholarly journals The role of the F-region vertical drift on the onset time of the equatorial spread F over Ilorin, Nigeria

2019 ◽  
Vol 128 (5) ◽  
Author(s):  
O A Oladipo ◽  
J O Adeniyi ◽  
I A Adimula ◽  
A O Olawepo ◽  
A Olowookere ◽  
...  
Keyword(s):  
Onset Time ◽  
Equatorial Spread F ◽  
F Region ◽  
Vertical Drift ◽  
Spread F

Spread F echoes variability along solar flux and seasonality conditions over the 50-MHz radar on Christmas Island

2015 ◽  
Author(s):  
R. Y. C. Cueva ◽  
F. S. Rodrigues ◽  
E. R. de Paula ◽  
R. T. Tsunoda ◽  
K. M Groves ◽  
...  
Keyword(s):  
Solar Flux ◽  
Christmas Island ◽  
Spread F

scholarly journals Timing of Mouse Molar Formation Is Independent of Jaw Length Including Retromolar Space

2021 ◽  
Vol 9 (1) ◽  
pp. 8
Author(s):  
Daisy (Jihyung) Ko ◽  
Tess Kelly ◽  
Lacey Thompson ◽  
Jasmene K. Uppal ◽  
Nasim Rostampour ◽  
...  
Keyword(s):  
Onset Time ◽  
Ct Scanning ◽  
Micro Ct ◽  
Third Molars ◽  
Developmental Duration ◽  
Dental Lamina ◽  
Permanent Molars ◽  
Dental Epithelium ◽  
Space Conditions

For humans and other mammals to eat effectively, teeth must develop properly inside the jaw. Deciphering craniodental integration is central to explaining the timely formation of permanent molars, including third molars which are often impacted in humans, and to clarifying how teeth and jaws fit, function and evolve together. A factor long-posited to influence molar onset time is the jaw space available for each molar organ to form within. Here, we tested whether each successive molar initiates only after a minimum threshold of space is created via jaw growth. We used synchrotron-based micro-CT scanning to assess developing molars in situ within jaws of C57BL/6J mice aged E10 to P32, encompassing molar onset to emergence. We compared total jaw, retromolar and molar lengths, and molar onset times, between upper and lower jaws. Initiation time and developmental duration were comparable between molar upper and lower counterparts despite shorter, slower-growing retromolar space in the upper jaw, and despite size differences between upper and lower molars. Timing of molar formation appears unmoved by jaw length including space. Conditions within the dental lamina likely influence molar onset much more than surrounding jaw tissues. We theorize that molar initiation is contingent on sufficient surface area for the physical reorganization of dental epithelium and its invagination of underlying mesenchyme.

scholarly journals Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

2008 ◽  
Vol 26 (7) ◽  
pp. 1751-1757 ◽  
Author(s):  
S. V. Thampi ◽  
S. Ravindran ◽  
T. K. Pant ◽  
C. V. Devasia ◽  
R. Sridharan
Keyword(s):  
Seasonal Variability ◽  
Seasonal Pattern ◽  
Onset Time ◽  
Critical Value ◽  
Latitudinal Gradients ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Spread F ◽  
Spread F ◽  
Definite Role

Abstract. In an earlier study, Thampi et al. (2006) have shown that the strength and asymmetry of Equatorial Ionization Anomaly (EIA), obtained well ahead of the onset time of Equatorial Spread F (ESF) have a definite role on the subsequent ESF activity, and a new "forecast parameter" has been identified for the prediction of ESF. This paper presents the observations of EIA strength and asymmetry from the Indian longitudes during the period from August 2005–March 2007. These observations are made using the line of sight Total Electron Content (TEC) measured by a ground-based beacon receiver located at Trivandrum (8.5° N, 77° E, 0.5° N dip lat) in India. It is seen that the seasonal variability of EIA strength and asymmetry are manifested in the latitudinal gradients obtained using the relative TEC measurements. As a consequence, the "forecast parameter" also displays a definite seasonal pattern. The seasonal variability of the EIA strength and asymmetry, and the "forecast parameter" are discussed in the present paper and a critical value for has been identified for each month/season. The likely "skill factor" of the new parameter is assessed using the data for a total of 122 days, and it is seen that when the estimated value of the "forecast parameter" exceeds the critical value, the ESF is seen to occur on more than 95% of cases.

Gamma-ray spectrometer calibration for field analysis of thorium, uranium and potassium

1970 ◽  
Vol 7 (4) ◽  
pp. 1093-1098 ◽  
Author(s):  
P. G. Killeen ◽  
C. M. Carmichael
Keyword(s):  
Regression Analysis ◽  
Gamma Ray ◽  
Laboratory Analysis ◽  
In Situ Analysis ◽  
Field Analysis ◽  
Gamma Ray Spectrometer ◽  
Nonlinear Relation ◽  
Using Data ◽  
Spectrometer Calibration

The calibration of a portable three-channel gamma-ray spectrometer for in situ analysis of thorium, uranium, and potassium is discussed. A method of regression analysis is suggested as the best means of including all of the data available from the calibration stations. Calibration indicates a nonlinear relation between count rates obtained in the field and concentrations in parts per million obtained from laboratory analysis. The range of radioelement content must be taken into consideration and appropriate sets of calibration constants applied. As an example of the method, calibration constants are calculated for a portable gamma-ray spectrometer using data for the Blind River uranium region of Ontario.

Hedonic experiences at heritage attractions: the visitor’s perspective

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ana Carolina Bender ◽  
Manuela Guerreiro ◽  
Bernardete Dias Sequeira ◽  
Júlio Mendes
Keyword(s):  
Design Methodology ◽  
Theory And Practice ◽  
Structured Interviews ◽  
Content Type ◽  
Heritage Sites ◽  
Exploratory Approach ◽  
Hedonic Experience ◽  
Using Data

Purpose The purpose of this study is to explore the hedonic experience and its formation at heritage attractions. Design/methodology/approach A qualitative and exploratory approach was applied, using data from 21 semi-structured interviews and three in-situ focus groups. Findings Findings highlight that senses, imagery and emotions are stimulated by the physical landscape and by triggers of memorable experiences. Research limitations/implications To further explore this topic, a broader range of heritage attractions and perspectives from the diverse stakeholders involved in the management and consumption of these sites is needed. Originality/value Given the scarcity of research dedicated to the hedonic experience at heritage sites, this study provides a contribution by exploring the visitor’s perspective and points out relevant insights. As the hedonic feelings of pleasure, comfort and related affective responses impact the quality of memorable experiences, relevant implications for theory and practice are discussed.

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