Hyperlipidemia associated with obesity is closely related to the development of atherosclerosis. Both n-3 polyunsaturated fatty acids (PUFAs) and long-chain monounsaturated fatty acids (MUFAs; i.e., ...C20:1 and C22:1 isomers) supplementation modulate risk factors for metabolic syndrome via multiple mechanisms, including the restoration of impaired lipid metabolism. We therefore examined the effects of pollock oil, which contains a considerable amount of n-3 PUFAs as well as long-chain MUFAs, on plasma hyperlipidemia and hepatic steatosis in diet-induced obese mice.
Male C57BL/6J mice (24-26 g) were divided into two groups (n = 10/group) and were fed a high-fat diet containing 32% lard (control group) or 17% lard plus 15% pollock oil (experimental group) for 6 weeks. For both groups, fat comprised 60% of the total caloric intake.
Although body and liver masses for the two groups did not differ significantly, hepatic lipids concentrations (triglycerides and total cholesterols) were lower (P < 0.05) after pollock oil ingestion. After 2 weeks on the specified diets, plasma lipid levels (total cholesterol, LDL cholesterol, and triglycerides) significantly decreased (P < 0.05) in the experimental group compared with the control group, although plasma HDL cholesterol levels did not differ. At the end of 6 weeks, plasma adiponectin levels increased (P < 0.05), whereas plasma resistin and leptin levels decreased (P < 0.05) in the experimental mice. Increased levels of long-chain MUFAs and n-3 PUFAs in plasma, liver and adipose tissue by ingesting pollock oil were possibly correlated to these favorable changes. Expression of hepatic genes involved in cholesterol metabolism (SREBP2, HMGCR, and ApoB) and lipogenesis (SREPB1c, SCD-1, FAS, and Acacα) was suppressed in the experimental group, and may have favorably affected hyperlipidemia and hepatic steatosis induced by the high-fat diet.
We demonstrated that pollock oil supplementation effectively improved hyperlipidemia, attenuated hepatic steatosis, and downregulated the express of hepatic genes involved in cholesterol and lipid metabolism in mice with diet-induced obesity.
► We present the starburst model of Snowball Earth events. ► Starburst periods of our galaxy coincide with the Snowball Earth events. ► We evaluate the effects of cosmic rays and dust particles ...during nebula encounters. ► Enhanced nebula encounters during the starburst can cause a Snowball Earth event. ► Direct evidence can be obtained from deep-sea sediments.
The trigger mechanism of the Snowball Earth events at 2.2–2.4Ga and 0.55–0.77Ga in the Proterozoic eon remains unknown despite intensive study over the last decade. We present the starburst model of the Snowball Earth. During a starburst of the Milky Way Galaxy, frequent and prolonged encounters with dark clouds and supernova remnants occur. The increased flux of cosmic dust particles and cosmic rays during the nebula encounters lead to a global super-cool climate, a Snowball Earth event. The individual nebula encounters may correspond to the substructures of super-cool/super-warm cycles in a Snowball Earth event. The starburst periods deduced from the ages of stars and star clusters coincide well with the Snowball Earth events reconstructed from geological records. We comprehensively evaluate the effects of cosmic rays, UV radiation, and cosmic dust particles during nebula encounters for the first time, and found that the starburst model of Snowball Earth events can adequately explain the triggering and occurrence pattern of Snowball Earth events. The direct evidence of nebula encounters can be obtained from deep-sea sediments deposited during the Snowball Earth events.
Great magnetic storms are recorded as aurora sightings in historical documents. The earliest known example of “prolonged” aurora sightings, with aurora persistent for two or more nights within a 7 ...day interval at low latitudes, in Japan was documented on 21–23 February 1204 in Meigetsuki, when a big sunspot was also recorded in China. We have searched for prolonged events over the 600 year interval since 620 in Japan based on the catalogue of Kanda and over the 700 year interval since 581 in China based on the catalogues of Tamazawa et al. (2017) and Hayakawa et al. (2015). Before the Meigetsuki event, a significant fraction of the 200 possible aurora sightings in Sòng dynasty (960–1279) of China was detected at least twice within a 7 day interval and sometimes recurred with approximately the solar rotation period of 27 days. The majority of prolonged aurora activity events occurred around the maximum phase of solar cycles rather than around the minimum, as estimated from the 14C analysis of tree rings. They were not reported during the Oort Minimum (1010–1050). We hypothesize that the prolonged aurora sightings are associated with great magnetic storms resulting from multiple coronal mass ejections from the same active region. The historical documents therefore provide useful information to support estimation of great magnetic storm frequency, which are often associated with power outages and other societal concerns.
Key Points
The earliest known example of prolonged aurora sightings in Japan was documented on 21–23 February 1204
Majority of the prolonged aurora activity events in China (900–1200) occurred around solar maxima rather than solar minima
The prolonged aurora activity events did not occur during the Oort Minimum (1010–1050)
Volcanoes with silica-rich and highly viscous magma tend to produce violent explosive eruptions that result in disasters in local communities and that strongly affect the global environment. We ...examined the timing of 11 eruptive events that produced silica-rich magma from four volcanoes in Japan (Mt. Fuji, Mt. Usu, Myojin-sho, and Satsuma-Iwo-jima) over the past 306
years (from AD 1700 to AD 2005). Nine of the 11 events occurred during inactive phases of solar magnetic activity (solar minimum), which is well indexed by the group sunspot number. This strong association between eruption timing and the solar minimum is statistically significant to a confidence level of 96.7%. This relationship is not observed for eruptions from volcanoes with relatively silica-poor magma, such as Izu-Ohshima. It is well known that the cosmic-ray flux is negatively correlated with solar magnetic activity, as the strong magnetic field in the solar wind repels charged particles such as galactic cosmic rays that originate from outside of the solar system. The strong negative correlation observed between the timing of silica-rich eruptions and solar activity can be explained by variations in cosmic-ray flux arising from solar modulation. Because silica-rich magma has relatively high surface tension (~
0.1
Nm
−1), the homogeneous nucleation rate is so low that such magma exists in a highly supersaturated state without considerable exsolution, even when located relatively close to the surface, within the penetration range of cosmic-ray muons (1–10
GeV). These muons can contribute to nucleation in supersaturated magma, as documented by many authors studying a bubble chamber, via ionization loss. This radiation-induced nucleation can lead to the pre-eruptive exsolution of H
2O in the silica-rich magma. We note the possibility that the 1991 Mt. Pinatubo eruption was triggered by the same mechanism: an increase in cosmic-ray flux triggered by Typhoon Yunya, as a decrease in atmospheric pressure results in an increase in cosmic-ray flux. We also speculate that the snowball Earth event was triggered by successive large-scale volcanic eruptions triggered by increased cosmic-ray flux due to nearby supernova explosions.
An anti-correlation of silica-rich magma eruptions and solar magnetic activity is found: Eight out of eleven eruptions took place in the period when the sun is not active. This anti-correlation suggests that silica-rich magma eruptions are triggered by bubble nucleation in magma, induced by cosmic-ray muons. Violent destruction of magma dome in a conduit is triggered when production rate,
J
rad, of the possible nucleation site exceeds the quenching rate,
Q
max.
Display omitted
► An anti-correlation of silica-rich magma eruptions solar magnetic activity is found. ►Nucleation of bubbles in supersaturated magma, induced by cosmic-ray muons, may lead to an explosive eruption. ► 1991 Mt. Pinatubo eruption may be triggered by an increase in cosmic-ray flux by Typhoon.
We investigate the 11‐year solar cycle during the Spoerer Minimum (1415–1534 A.D.) by measuring the carbon 14 content in the annual tree rings for the period 1413–1554 A.D. The period of the Spoerer ...Minimum is assumed to be a prolonged sunspot minimum like the Maunder Minimum (1645–1715 A.D.). However, the 11‐year solar cycle, which appears in recent solar variations, was also prominently detected in the carbon 14 record during this period. The amplitude of the 11‐year cycle seems to have been modulated only around 1455–1510 A.D.
This paper presents the features of the 'eleven-year' cycle of radiocarbon content during the period of prolonged sunspot minimum called the Maunder Minimum (1645-1715 AD). Whether or not the Sun had ...maintained the cyclic polarity reversal even during the Maunder Minimum has been a controversial topic for a long time. Although persistency of the cyclicity has been investigated by using cosmogenic isotopes or by calculations, a consistent description has not been obtained so far. Hence, we have obtained a new record of carbon-14 content in tree rings from 1631-1739 AD, and made a comparison with the record previously obtained. Periods of 13-15 and 24-29 years detected in the variation of carbon-14 content seem to be suggesting that the Sun had retained periodic polarity reversal during this prolonged minimum with slightly longer periodicity than that of recent intense solar activity. Our results seem to support the inverse correlation between the intensity and the cycle length of solar activity.
The North Pacific Gyre Oscillation (NPGO) significantly imprints on hydrological fluctuations of the East Asian summer monsoon (EASM) region, but this has not yet been observed in proxy-based ...hydroclimate reconstructions. This study reports a tree-ring cellulose oxygen isotope (δ
18
O) record from northeastern Japan spanning A.D. 1927–2010, overlapping with instrumental data, which we analyzed to determine if tree-ring δ
18
O in northeastern Japan records a signal consistent with the NPGO. Our results indicate that the tree-ring δ
18
O has a significant negative correlation with May–June (MJ) precipitation, as well as with short-term MJ relative humidity variation. Time-lagged temporal-domain comparisons indicate that the tree-ring δ
18
O is significantly correlated with the following year March–April (MA) and MJ NPGO index before the North Pacific climate transition in the late 1980s, particularly on decadal timescales. These relationships between our tree-ring δ
18
O and the climate patterns in the North Pacific are consistent with the actual early-summer precipitation. Spatial spring and early-summer sea-surface temperature anomalies exhibit a NPGO-like pattern in the following year. Spatial early-summer sea-level pressure anomalies also indicate North Pacific Oscillation (NPO) like patterns in the western North Pacific. These results suggest a lagged response of the NPGO to the EASM climate changes, and tree-ring δ
18
O in northeast Japan has a potential linkage with NPGO index from winter to early summer of the following year.
We examined the effect of the 11-year solar cycle and quasi-biennial oscillation (QBO) on the ∼27-day solar rotational period detected in tropical convective cloud activity. We analyzed the data of ...outgoing longwave radiation (OLR) for AD1979–2004, dividing into four different cases by the combination of high and low solar activities in terms of the 11-year variation, and easterly and westerly stratospheric winds associated with QBO. As a result, ∼27-day variation has been most significantly detected in high solar activity period around the Indo-Pacific Warm Pool. Based on correlation analysis, we find that solar rotation signal can explain 10–20% of OLR variability around the tropical warm pool region during the high solar activity period. The spatial distribution has been, however, apparently different according to the phases of QBO. It is suggested that the 11-year solar cycle and stratospheric QBO have a possibility to cause large-scale oceanic dipole phenomena.
► We analyze ∼27-day solar rotational signal in cloud activity. ► ∼27-day signal is found near the tropical region in high solar activity period. ► The spatial distribution of solar signal is different from the QBO phases. ► The extent of QBO influence on cloud activity is different from the solar activity level. ► Solar activity and QBO may influence interannual oceanic dipole phenomena.
Saturation of StellarWinds from Young Suns Suzuki, Takeru K; Imada, Shinsuke; Kataoka, Ryuho ...
Publications of the Astronomical Society of Japan,
10/2013, Letnik:
65, Številka:
5
Journal Article
Recenzirano
Odprti dostop
We investigated mass losses via stellar winds from Sun-like main-sequence stars with a wide range of activity levels. We performed forward-type magnetohydrodynamical numerical experiments for Alfvén ...wave-driven stellar winds with a wide range of input Poynting flux from the photosphere. Increasing the magnetic field strength and the turbulent velocity at the stellar photosphere from the current solar level, the mass-loss rate rapidly at first increases, owing to suppression of the reflection of the Alfvén waves. The surface materials are lifted up by the magnetic pressure associated with the Alfvén waves, and the cool dense chromosphere is intermittently extended to 10%–20% of the stellar radius. The dense atmospheres enhance the radiative losses, and eventually most of the input Poynting energy from the stellar surface escapes by radiation. As a result, there is no more sufficient energy remaining for the kinetic energy of the wind; the stellar wind saturates in very active stars, as observed in Wood et al. (2002, ApJ, 574, 412; 2005, ApJ, 628, L143). The saturation level is positively correlated with Br,0f0
, where Br,0
and f0
are the magnetic field strength and the filling factor of open flux tubes at the photosphere. If Br,0f0
is relatively large ≳5G, the mass-loss rate could be as high as 1000 times. If such a strong mass loss lasts for ∼1 billion years, the stellar mass itself would be affected, which could be a solution to the faint young Sun paradox. We derived a Reimerstype scaling relation that estimates the mass-loss rate from an energetics consideration of our simulations. Finally, we derived the evolution of the mass-loss rates, Ṁ∝t
-1.23, of our simulations, combining with an observed time evolution of X-ray flux from Sun-like stars, which are shallower than Ṁ∝t
-2.33±0.55 in Wood et al. (2005).
PDF
