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Nagashima, K.

Publications and source records attributed to Nagashima, K..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Sub-Zero Alteration in an Isotopically Heavy Brine Preserved in a Pristine H Chondrite Xenolith

Introduction: Brecciated H chondrites host a variety of xenoliths, including unshocked, phyllo- silicate-rich carbonaceous chondrites (CCs). The brecciated H chondrite Zag (H3-6) is one of two chondrites to host macroscopic (1 - 5mm), xenolithic crystals of halite (NaCl) with aqueous fluid inclusions and organics. A ~1cm CC xenolith in Zag (Zag clast) has mineralogy similar to CI chondrites, but it has a unique bulk oxygen isotopic composition among all meteorites (Δ(exp 17)O = 1.49 ± 0.04 ‰, δ(exp 18)O = 22.38 ± 0.17 ‰). The Zag clast encloses halite in its matrix, linking the coarse, matrix halite and the xenolith to the same parent object, suggested to be hydrovolcanically active. Its bulk C and N contents are the highest among chondrites and bulk δ(exp 15)N is similar to CR chondrites and Bells. Insoluble organic material (IOM) in the Zag clast has δD and δ(exp 15)N “hotspots”, also similar to CR chondrites and Bells (C2-ung.). We provide further isotopic characterization of the Zag clast to constrain the formation temperature and origin of its primary and secondary components.

Frank, D. R.↗
NASA NTRS2020

Isotopes of H, N, and O in H Chondrite Xenoliths

Brecciated H chrondites host a variety of xenoliths, including unshocked, phyllosilate-rich carbonaceous chondrites (CCs) [1-2]. The brecciated H chondrite Zag (H3-6) is one of two chondrites to host macroscopic (1 - 5mm), xenolithic crystals of halite (NaCl) with aqueous fluid inclusions and organics [3-4]. A ~1cm CC xenolith in Zag (Zag clast) also encloses halite in its matrix, linking the halite and the xenolith to the same parent object. The Zag clast has mineralogy similar to CI chondrites, but it has a unique bulk oxygen isotopic composition among all meteorites (Δ17O = 1.49 ± 0.04 ‰, 𝛿18O = 22.38 ± 0.17 ‰) and is therefore derived from a uniquely sampled parent object [5-6]. Organics have high bulk 𝛿D and 𝛿15N values with isotopic "hotspots" similar to organics in CR chondrites and Bells (C2-ung.) [6-7]. Bulk 𝛿15N is also similar to CRs and Bells [7]. We provide further isotopic characterization of the Zag clast to constrain the formation temperature and origin of its primary and secondary components.

Frank, D.↗
NASA NTRS2017

Oxygen, Magnesium, and Aluminum Isotopes in the Ivuna CAI: Re-Examining High-Temperature Fractionations in CI Chondrites

CI chondrites are thought to approximate the bulk solar system composition since they closely match the composition of the solar photosphere. Thus, chemical differences between a planetary object and the CI composition are interpreted to result from fractionations of a CI starting composition. This interpretation is often made despite the secondary mineralogy of CI chondrites, which resulted from low-T aqueous alteration on the parent asteroid(s). Prevalent alteration and the relatively large uncertainties in the photospheric abundances (approx. +/-5-10%) permit chemical fractionation of CI chondrites from the bulk solar system, if primary chondrules and/or CAIs have been altered beyond recognition. Isolated olivine and pyroxene grains that range from approx. 5 microns to several hundred microns have been reported in CI chondrites, and acid residues of Orgueil were found to contain refractory oxides with oxygen isotopic compositions matching CAIs. However, the only CAI found to be unambiguously preserved in a CI chondrite was identified in Ivuna. The Ivuna CAI's primary mineralogy, small size (approx.170 microns), and fine-grained igneous texture classify it as a compact type A. Aqueous alteration infiltrated large portions of the CAI, but other regions remain pristine. The major primary phases are melilite (Ak 14-36 ), grossmanite (up to 20.8 wt.% TiO 2 ), and spinel. Both melilite and grossmanite have igneous textures and zoning patterns. An accretionary rim consists primarily of olivine (Fa 2-17 ) and low-Ca pyroxene (Fs 2-10 ), which could be either surviving CI2 material or a third lithology.

Frank, D. R.↗
NASA NTRS2001

Increased renal tubular sodium reabsorption during exercise-induced hypervolemia in humans

We tested the hypothesis that renal tubular Na(+) reabsorption increased during the first 24 h of exercise-induced plasma volume expansion. Renal function was assessed 1 day after no-exercise control (C) or intermittent cycle ergometer exercise (Ex, 85% of peak O(2) uptake) for 2 h before and 3 h after saline loading (12.5 ml/kg over 30 min) in seven subjects. Ex reduced renal blood flow (p-aminohippurate clearance) compared with C (0.83 +/- 0.12 vs. 1.49 +/- 0.24 l/min, P < 0.05) but did not influence glomerular filtration rates (97 +/- 10 ml/min, inulin clearance). Fractional tubular reabsorption of Na(+) in the proximal tubules was higher in Ex than in C (P < 0.05). Saline loading decreased fractional tubular reabsorption of Na(+) from 99.1 +/- 0.1 to 98.7 +/- 0.1% (P < 0.05) in C but not in Ex (99.3 +/- 0.1 to 99.4 +/- 0.1%). Saline loading reduced plasma renin activity and plasma arginine vasopressin levels in C and Ex, although the magnitude of decrease was greater in C (P < 0.05). These results indicate that, during the acute phase of exercise-induced plasma volume expansion, increased tubular Na(+) reabsorption is directed primarily to the proximal tubules and is associated with a decrease in renal blood flow. In addition, saline infusion caused a smaller reduction in fluid-regulating hormones in Ex. The attenuated volume-regulatory response acts to preserve distal tubular Na(+) reabsorption during saline infusion 24 h after exercise.

NASA Discipline Cardiopulmonary↗
NASA NTRS1985

Cosmic ray sidereal diurnal variation of galactic origin observed by neutron monitors

Cosmic ray sidereal diurnal variations observed by neutron monitors are analyzed for the period 1961 to 1978, by adding 134 station years data to the previous paper (Nagashima, et al., 1983). Also the dependence of the sidereal variations on Sun's polar magnetic field polarity is examined for two periods; the period of negative polarity in the northern region, 1961 to 1969 and the period of positive polarity, 1970 to 1978. It is obtained that for the former period, the amplitude A=0.0203 + or 0.0020% and the phase phi=6.1 + or - 0.4 h LST and for the latter period, 0.0020% and phi=8.6 + or - 4 h LST, respectively.

Ishida, Y.↗
NASA NTRS1985

Sidereal anisotropies in the median rigidity range 60-600GV in 1978-1983

Observed sidereal variations are corrected for the influence of spurious variation by a method using the antisidereal diurnal variations produced from the same 2nd order anisotropy (Nagashima, et al., 1983). It is demonstrated that the corrected variations are a resultant product of two constituents of galactic origin: one is north-south (N-S) symmetric and the other is N-S asymmetric.

Ueno, H.↗
NASA NTRS1985

Corrected sidereal anisotropy for underground moons

Data from underground muon telescopes in New Mexico and Bolivia are analyzed in sidereal time and anti-sidereal time in the rigidity range 20 GV to a few 100's of GV. Using both vertical and north- and south- pointing telescopes in both hemispheres, a latitude range of 70 N to 50 S is covered. It is shown that there is an anti-sidereal variation of the P 1 over 2 type, having opposite phase in the Northern and Southern Hemispheres, and maximum amplitude at mid latitudes. The anti-sidereal data are used to correct the sidereal data, using the Nagashima method (Nagashima, 1984); the resulting corrected sidereal vectors for northern hemisphere telescopes have their sidereal maxima close to 3h sidereal time, in reasonable agreement with sidereal data at higher energies from small air showers. The Nagashima correction also eliminates effects due to the reversal of the Sun's polar magnetic field which show up in the uncorrected sidereal data.

Swinson, D. B.↗
NASA NTRS1985

The first three harmonics of solar daily variation caused by the diffusive propagation of galactic cosmic rays through the heliosphere

Some results for the first three harmonics derived from the simulation of diffusion convection of galactic cosmic rays is presented. Also, some dependences of the results to the modulation parameters are presented. The results are discussed in comparison with observations and with the former studies of higher order anisotropy. In addition to this, the existence is suggested of the IMF-sense-dependent anisotropy of higher order.

Munakata, K.↗
NASA NTRS1985

Formulation of cosmic-ray solar daily variation and its seasonal variation, produced from generalized stationary anisotropy of solar origin

In previous papers, a formulation was presented of cosmic ray daily variations produced from solar anisotropies stationary through a year, and also of their annual (or seasonal) modulation caused by the annual variation of the rotation axis of the Earth relative to that of the Sun. These anisotropies are symmetric for an arbitrary rotation around an axis. From observations of the tri-diurnal variation, it has been suggested that solar anisotropies also contain some axis-asymmetric term of the third order with respect to the IMF-axis. This suggestion has recently found support in a theoretical study by Munakata and Nagashima. According to their results, the terms of axis-asymmetry with respect to IMF-axis appear also in the 2nd order anisotropy, together with some different kinds of axis-symmetric terms. The contribution of these anisotropies to the daily variation is different from that of those discussed previously. The above mentioned formulation is extended to a case of a generalized anisotropy.

Tatsuoka, R.↗
NASA NTRS1985

Solar tri-diurnal variation of cosmic rays in a wide range of rigidity

Solar tri-diurnal variations of cosmic rays have been analyzed in a wide range of rigidity, using data from neutron monitors, and the surface and underground muon telescopes for the period 1978-1983. The rigidity spectrum of the anisotropy in space is assumed to be of power-exponential type as (P/gamma P sub o) to the gamma exp (gamma-P/P sub o). By means of the best-fit method between the observed and the expected variations, it is obtained that the spectrum has a peak at P (=gamma P sub o) approx = 90 GV, where gamma=approx 3.0 and P sub o approx. 30 GV. The phase in space of the tri-diurnal variation is also obtained as 7.0 hr (15 hr and 23 hr LT), which is quite different from that of approx. 1 hr. arising from the axisymmetric distribution of cosmic rays with respect to the IMF.

Mori, S.↗
NASA NTRS1985

Anomalous increase of solar anisotropy above 150GV in 1981-1983

An analysis was carried out of the observed data with Nagoya (surface). Misato (34mwe) and Sakashita (80mwe) multidirectional muon telescope, for the solar activity maximum period of 1978-1983. These data respond to primaries extending over the median rigidity range 60GV to 600GV. The observed amplitude at Sakashita station in 1981-1983 increased, especially in 1982; the amplitude is twice as large as that in 1978-1980, when those at Nagoya and Misato stations are nearly the same as those in 1978-1980. Uni-directional anisotropy is derived by the best fit method by assuming the flat rigidity spectrum with the upper cutoff rigidity Pu. The value of Pu obtained is 270GV in 1981-1983 and 150GV in 1978-1980.

Ueno, H.↗
NASA NTRS1985

Rigidity spectrum of Forbush decrease

Using data from neutron monitors and muon telescopes at surface and underground stations, the average rigidity spectrum of Forbush decreases (Fds) during the period of 1978-1982 were obtained. Thirty eight Ed-events are classified into two groups Hard Fd and Soft Fd according to size of Fd at Sakashita station. It is found that a spectral form of fractional-power type (P to the-gamma sub 1 (P+P sub c) to the -gamma sub2) is more suitable for the present purpose than that of power-exponential type or of power type with an upper limiting rigidity. The best fitted spectrum of fractional-power type is expressed by gamma sub1 = 0.37, gamma sub2 = 0.89 and P subc = 10 GV for Hard Fd and gamma sub1 = 0.77, gamma sub2 = 1.02 and P sub c - 14GV for Soft Fd.

Sakakibara, S.↗