scholarly journals Radioactive equilibria and disequilibria of U-series nuclides in the products from Izu arc volcanoes, Japan

2011 ◽  
Vol 1 (1) ◽  
pp. 335-338
Author(s):  
Y. Kurihara ◽  
M. Takahashi ◽  
J. Sato
Keyword(s):  
Activity Ratio ◽  
Basaltic Magma ◽  
Radioactive Equilibrium ◽  
Rhyolitic Magma ◽  
Arc Volcanism ◽  
Magma Genesis ◽  
The Earth ◽  
Short Period ◽  
Activity Ratios ◽  
Subducting Slab

Abstract Activity ratios among 238U-230Th-226Ra in the products from Izu arc volcanoes, Japan, were observed in order to estimate the time scale of magmatic processes and the magma generation for Izu arc volcanism. Activity ratios of 238U/230Th and 226Ra/230Th in the basaltic and andesitic products from Izu arc volcanoes were greater than unity, being enriched in 238U and 226Ra relative to 230Th. The 226Ra/230Th activity ratio versus 238U/230Th activity ratio diagram for these products showed positive correlation, suggesting that the 238U-230Th-226Ra disequilibria occurred during the magma genesis by the additions of U- and Ra-rich fluids derived from the subducting slab by dehydration to the mantle wedge. The 230Th-226Ra radioactive disequilibria observed in the basaltic and andesitic products imply a short period of time (<8000 years) between the magma genesis and the eruption. The majority of rhyolitic products was considered to be almost in equilibrium of 238U=230Th=226Ra. The observation that 238U-230Th-226Ra for the rhyolite are in radioactive equilibrium suggested that the rhyolitic magma from Izu arc was generated in the partial melting of the earth crust heated by the basaltic magma of high temperature.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

BASALTIC MAGMA GENESIS AND MANTLE SOURCES BENEATH TWO CENOZOIC VOLCANOES, MT. EARLY AND SHERIDAN BLUFF, EAST ANTARCTICA

2020 ◽  
Author(s):  
Yuyu Li ◽  
◽  
K.S. Panter ◽  
John L. Smellie ◽  
Jerzy S. Blusztajn ◽  
...  
Keyword(s):  
Basaltic Magma ◽  
East Antarctica ◽  
Magma Genesis ◽  
Mantle Sources

scholarly journals New Tools for the Optimized Follow-Up of Imminent Impactors

Universe ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 10
Author(s):  
Maddalena Mochi ◽  
Giacomo Tommei
Keyword(s):  
Orbit Determination ◽  
Main Belt ◽  
Impact Monitoring ◽  
The Earth ◽  
Current Observation ◽  
Short Period ◽  
Fly Eye ◽  
Near Earth Asteroids ◽  
Near Earth Objects

The solar system is populated with, other than planets, a wide variety of minor bodies, the majority of which are represented by asteroids. Most of their orbits are comprised of those between Mars and Jupiter, thus forming a population named Main Belt. However, some asteroids can run on trajectories that come close to, or even intersect, the orbit of the Earth. These objects are known as Near Earth Asteroids (NEAs) or Near Earth Objects (NEOs) and may entail a risk of collision with our planet. Predicting the occurrence of such collisions as early as possible is the task of Impact Monitoring (IM). Dedicated algorithms are in charge of orbit determination and risk assessment for any detected NEO, but their efficiency is limited in cases in which the object has been observed for a short period of time, as is the case with newly discovered asteroids and, more worryingly, imminent impactors: objects due to hit the Earth, detected only a few days or hours in advance of impacts. This timespan might be too short to take any effective safety countermeasure. For this reason, a necessary improvement of current observation capabilities is underway through the construction of dedicated telescopes, e.g., the NEO Survey Telescope (NEOSTEL), also known as “Fly-Eye”. Thanks to these developments, the number of discovered NEOs and, consequently, imminent impactors detected per year, is expected to increase, thus requiring an improvement of the methods and algorithms used to handle such cases. In this paper we present two new tools, based on the Admissible Region (AR) concept, dedicated to the observers, aiming to facilitate the planning of follow-up observations of NEOs by rapidly assessing the possibility of them being imminent impactors and the remaining visibility time from any given station.

scholarly journals Temporal Evolution of Cooling by Natural Convection in an Enclosed Magma Chamber

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 108
Author(s):  
Carlos Enrique Zambra ◽  
Luciano Gonzalez-Olivares ◽  
Johan González ◽  
Benjamin Clausen
Keyword(s):  
Natural Convection ◽  
Magma Chamber ◽  
Temporal Evolution ◽  
Basaltic Magma ◽  
Boussinesq Equations ◽  
Rhyolitic Magma ◽  
The Times ◽  
Volume Method ◽  
The Mathematical Model ◽  
Liquid Magma

This research numerically studies the transient cooling of partially liquid magma by natural convection in an enclosed magma chamber. The mathematical model is based on the conservation laws for momentum, energy and mass for a non-Newtonian and incompressible fluid that may be modeled by the power law and the Oberbeck–Boussinesq equations (for basaltic magma) and solved with the finite volume method (FVM). The results of the programmed algorithm are compared with those in the literature for a non-Newtonian fluid with high apparent viscosity (10–200 Pa s) and Prandtl (Pr = 4 × 104) and Rayleigh (Ra = 1 × 106) numbers yielding a low relative error of 0.11. The times for cooling the center of the chamber from 1498 to 1448 K are 40 ky (kilo years), 37 and 28 ky for rectangular, hybrid and quasi-elliptical shapes, respectively. Results show that for the cases studied, natural convection moved the magma but had no influence on the isotherms; therefore the main mechanism of cooling is conduction. When a basaltic magma intrudes a chamber with rhyolitic magma in our model, natural convection is not sufficient to effectively mix the two magmas to produce an intermediate SiO2 composition.

scholarly journals Effectiveness Analysis of Working Capital on MSME Handycraft

2019 ◽  
Vol 1 (1) ◽  
pp. 127-133
Author(s):  
Laras Nada Wahyu Atika ◽  
Agus Sukoco
Keyword(s):  
Research Method ◽  
Qualitative Data ◽  
Activity Ratio ◽  
Business Development ◽  
Working Capital ◽  
Current Ratio ◽  
Working Capital Management ◽  
Business Operations ◽  
Effectiveness Analysis ◽  
Activity Ratios

This study aims to determine the effectiveness of working capital management in MSME Rozatajaya Souvenir in Sidoarjo through the analysis of liquidity and activity ratios. The research method is using descriptive qualitative. Data obtained from financial transaction records for two semesters of 2018. The results of this study found that the average Liquidity Ratio was very good which included Current Ratio of 3.02, Quick Ratio of 2.93 and Cash Ratio of 2.25. The effectiveness of working capital using the Activity Ratio was considered less effective including the average Working Capital Turnover of 1.23, Receivable Turnover of 4.22 and Turnover Inventory of 14.95 times. The findings of this study, working capital is very necessary for business operations, however, management of working capital is still not effective so it requires a strategy to increase the effectiveness of working capital in business development.

scholarly journals Radar Observations of Comet Nuclei and Comae

2005 ◽  
Vol 13 ◽  
pp. 763-763
Author(s):  
Donald B. Campbell ◽  
John K. Harmon ◽  
Micael C. Nolan ◽  
Steven J. Ostro
Keyword(s):  
Cross Sections ◽  
Cometary Nucleus ◽  
Size Distributions ◽  
Radar Systems ◽  
The Earth ◽  
Radar Cross Sections ◽  
Short Period ◽  
Grain Size Distributions ◽  
Resolution Imaging

Nine comets have been detected with either the Arecibo (12.6 cm wavelength) or Goldstone (3.5 cm) radar systems. Included are six nucleus detections and five detections of echoes from coma grains. The radar backscatter cross sections measured for the nuclei correlate well with independent estimates of their sizes and are indicative of surface densities in the range of 0.5 to 1.0 g cm-3. Like most asteroids, comets appear to have surfaces that are very rough at scales much larger than the radar wavelength. Coma echo models can explain the radar cross sections using grain size distributions that include a substantial population of cm-sized grains. A long term goal of the cometary radar program has been the high resolution imaging of a cometary nucleus. Eleven short period comets are potentially detectable over the next two decades a few of which may be suitable for imaging. We are always waiting for the arrival of a new comet with an orbit that brings it within 0.1 AU of the earth.

Modulation by adrenalectomy and fasting of insulin effects in perfused hindlimb muscle

1982 ◽  
Vol 242 (5) ◽  
pp. E323-E329
Author(s):  
H. Shikama ◽  
D. T. Chu ◽  
J. H. Exton
Keyword(s):  
Glycogen Content ◽  
Activity Ratio ◽  
Glycogen Synthase ◽  
Hexose Transport ◽  
Fasted State ◽  
Hindlimb Muscle ◽  
Maximal Activation ◽  
Activity Ratios ◽  
Adrenalectomized Rats

Perfused hindlimb muscle from fed adrenalectomized rats accumulated more 2-deoxyglucose at submaximal concentrations of insulin in comparison to muscle from fed normal rats. However, in the fasted state, insulin-stimulated 2-deoxyglucose uptake was largely inhibited by adrenalectomy. Basal 2-deoxyglucose uptake did not differ between fed and fasted normal or adrenalectomized rats. The changes in insulin effects caused by adrenalectomy were due to altered hexose transport as shown by measurements of 3-O-methylglucose uptake and of intracellular free and phosphorylated 2-deoxyglucose. Muscles of fasted normal and fed or fasted adrenalectomized rats showed higher basal glycogen synthase --glucose-6-P/+glucose-6-P activity ratios than those of fed normal rats probably because of decreased glycogen content. However, muscles from fed or fasted adrenalectomized rats did not show any alterations in insulin effects on the activity ratio and half-maximal activation constant (A0.5) for glucose-6-P of glycogen synthase. Because of the dissociation of the effects of insulin on hexose transport and glycogen synthase in muscle of fasted adrenalectomized rats, it is concluded that the impairment in insulin-stimulated hexose transport in these animals is due to a defect lying beyond the interaction of insulin with its receptor.

scholarly journals Investigation of the Orbital Stability of Minor Planets with Cometary Eccentricities

1972 ◽  
Vol 45 ◽  
pp. 431-436 ◽  
Author(s):  
G. A. Chebotarev ◽  
N. A. Belyaev ◽  
R. P. Eremenko
Keyword(s):  
Orbital Stability ◽  
Minor Planets ◽  
The Earth ◽  
Short Period ◽  
Account Information

The evolution of the orbits of 19 asteroids of particular interest has been studied over the interval 1660–2060, perturbations by Venus to Pluto being taken into account. Information was obtained about the encounters with Venus, the Earth, and Mars. A few approaches of Hidalgo to Jupiter were noted. In distinction to the orbits of short-period comets, the orbits of the 19 asteroids are stable throughout the 400-yr interval.

A cometary mechanism for the formation of tektites

1963 ◽  
Vol 272 (1351) ◽  
pp. 467-480 ◽  
Keyword(s):  
Small Eccentricity ◽  
The Earth ◽  
Short Period ◽  
Cometary Material ◽  
General Order ◽  
Order Of Magnitude

Passage of the Earth through a comet must occur on average every million years approximately and last for a time of a few hours. A proportion of short-period comets will have had sufficiently small eccentricity (less than about 0.6) for accretion of cometary material to occur during such passages and produce a narrow jet of material falling vertically down-wards through the atmosphere. The orbits of these comets are such that the jet would be most likely to fall within lower latitudes, as is found for tektite fields. The temperature within the accretion-stream would be sufficiently great to vaporize most materials, and the tektites are regarded as forming from the most refractory substances within the stream, so that they are not characteristic of cometary compositions. The speeds of entry into the atmosphere are high enough for ablation to occur, and the dimensions of the resulting fields and their total masses agree in general order of magnitude with those estimated for actual fields.

scholarly journals Further measurements on wireless waves received from the upper atmosphere

1927 ◽  
Vol 116 (775) ◽  
pp. 682-693 ◽  
Keyword(s):  
Closed Loop ◽  
Wave Length ◽  
Direct Proof ◽  
Relative Magnitude ◽  
Upper Atmosphere ◽  
Circle Plane ◽  
The Earth ◽  
Direction Finder ◽  
Short Period ◽  
Attention To Detail

In previous papers the authors have described the development of experimental methods of measuring the directions and relative intensities of both the electric and magnetic forces in wireless waves received at the earth’s surface from a distant transmitting station. In this work it was seen that the detection of the arrival of waves deflected from the upper atmosphere, and polarised with their electric force in a horizontal plane, was rendered difficult owing to the relatively great reflecting powTer of the earth resulting from its high conductivity. By a suitable choice of wave-length and careful attention to detail in the design and construction of the apparatus, however, the methods employed enabled measurements to be made on both vertically and horizontally polarised waves. The results of such measurements enabled a direct proof to be given of the fact that the fading of wireless signals on a vertical aerial and the variations of bearings experienced on the closed-loop type of wireless direction-finder are due to the reception respectively of vertically and horizontally polarised waves deflected from the upper atmosphere in their passage from the transmitter to the receiver. On arrival at the receiver, these indirect or atmospheric waves interfere with the direct or ground waves, in a manner determined by their relative magnitude and phase, and produce the intensity and apparent direc­tional variations mentioned above. The results of such interference phenomena have been investigated experimentally by Appleton and Barnett and by Holling-worth. In a more recent publication the present authors have provided experimental evidence showing that the path of the indirect waves is confined to the great circle plane between the transmitter and receiver. The measurements of the quantities in the received waves as previously described by the authors were confined to observations on the transmissions from the Bournemouth broadcasting station over a short period. The object of the present paper is to describe the continuation of these measurements and their extension to the transmissions from other stations.

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