A hybrid experiment consisting of emulsion chambers, burst detectors and the Tibet-II air-shower array was carried out at Yangbajing (4300 m a.s.l., 606 g/cm2) in Tibet to obtain the energy spectra ...of primary protons and heliums. From three-year operation, these energy spectra are deduced between 1015 and 1016 eV by triggering the air showers associated with a high energy core and using a neural network method in the primary mass separation. The proton spectrum can be expressed by a single power-law function with a differential index of −3.01±0.11 and −3.05±0.12 based on the QGSJET+HD and SIBYLL+HD models, respectively, which are steeper than that extrapolated from the direct observations of −2.74±0.01 in the energy range below 1014 eV. The absolute fluxes of protons and heliums are derived within 30% systematic errors depending on the hadronic interaction models used in Monte Carlo simulation. The result of our experiment suggests that the main component responsible for the change of the power index of the all-particle spectrum around 3×1015 eV, so-called “knee”, is composed of nuclei heavier than helium. This is the first measurement of the differential energy spectra of primary protons and heliums by selecting them event by event at the knee energy region.
We present the large-scale sidereal anisotropy of Galactic cosmic-ray intensity in the multi-TeV region observed with the Tibet-III air shower array during the period from 1999 through 2003. The ...sidereal daily variation of cosmic rays observed in this experiment shows an excess of relative intensity around 4-7 hr local sidereal time as well as a deficit around 12 hr local sidereal time. While the amplitude of the excess is not significant when averaged over all declinations, the excess in individual declination bands becomes larger and clearer as the viewing direction moves toward the south. The maximum phase of the excess intensity changes from similar to 7 hr at the Northern Hemisphere to similar to 4 hr at the equatorial region. We also show that both the amplitude and the phase of the first harmonic vector of the daily variation are remarkably independent of primary energy in the multi-TeV region. This is the first result determining the energy and declination dependences of the full 24 hr profiles of the sidereal daily variation in the multi-TeV region with a single air shower experiment.
Macrophage infiltration in obese adipose tissue provokes local inflammation and insulin resistance. Evidence has accumulated that activation of 11β-HSD1 in adipocytes is critically involved in ...dysfunction of adipose tissue. However, the potential role of 11β-HSD1 in macrophages still remains unclear. We here demonstrate that a murine macrophage cell line, J774.1 cells expressed 11β-HSD1 mRNA and reductase activity, both of which were augmented by lipopolysaccharide (LPS)-induced cell activation. Three kinds of pharmacological inhibition of 11β-HSD1 in LPS-treated macrophages significantly suppressed the expression and secretion of interleukin 1β, tumor necrosis factor α or monocyte chemoattractant protein 1, thereby highlighting a novel role of 11β-HSD1 in pro-inflammatory properties of activated macrophages.
We report the first systematic survey of cosmic ray precursors of geomagnetic storms. Our data set comprises the 14 “major” geomagnetic storms (peak Kp ≥ 8−) identified by Gosling et al. 1990 ...together with 25 large storms (peak Kp ≥ 7−) observed from 1992 through 1998. After eliminating events for which the muon detector network had poor coverage of the sunward interplanetary magnetic field (IMF) direction, we determined that 15 of the remaining 22 events (68%) had identifiable cosmic ray precursors with typical lead times ranging from 6 to 9 hours prior to the storm sudden commencement (SSC). Of the 15 precursors, 10 were of the “loss cone” (LC) type which is characterized by an intensity deficit confined to a narrow pitch angle region around the sunward IMF direction. Cosmic rays in the loss cone presumably originate in the cosmic‐ray‐depleted region downstream of the approaching shock. The remaining five precursors were of the “enhanced variance” (EV) type which is characterized by intensity increases or decreases that do not systematically align with the IMF direction. The incidence of precursors increases with storm size; for instance, 89% of storms with peak Kp greater than or equal to 8.0 had precursors. Our results show that the muon detector network can be a useful tool in space weather forecasting. However, new detector(s) installed to fill major gaps in the present network are urgently required for better understanding the nature of precursors and for reliable space weather forecasting.
Results of a steady TeV g-ray point-source search using data taken from the Tibet HD (1997 February -1999 September) and Tibet III (1999 November-2001 October) arrays are presented. From 0 to 60 in ...declination, significant excesses from the well-known steady source Crab Nebula and the high state of the flare-type source Markarian 421 are observed. Because the levels of significance from other positions are not sufficiently high, 90% confidence level upper limits on the flux are set assuming different power-law spectra. To allow cross-checking, two independently developed analyses are used in this work.
The wavelet transform technique has been applied to investigate the periodicities longer than a year in cosmic ray intensity variations observed at the Voyager spacecraft and at the Earth. We found ...significant similar to 1.7- and similar to 1.3- year periodic components in the cosmic ray intensity variation in the outer heliosphere during the 1980s (solar cycle 21) and the 1990s (solar cycle 22), respectively. This property is consistent with the result of the wavelet analysis of the cosmic ray intensity variations observed at several Neutron Monitors (NMs) and also with previous reports about these periodicities using several plasma parameters, such as the solar wind speed and geomagnetic indices, for example. As comparing with the interplanetary magnetic field (IMF) and solar flare indices, causal relation between energy release from the Sun and the similar to 1.7- year quasi-periodicity is suggested.
Leptin augments glucose and lipid metabolism independent of its effect on satiety. Administration of leptin in rodents increases skeletal muscle beta-oxidation by activating AMP-activated protein ...kinase (AMPK). We previously reported that, as hyperleptinemic as obese human subjects, transgenic skinny mice overexpressing leptin in liver (LepTg) exhibit enhanced insulin sensitivity and lipid clearance. To assess skeletal muscle AMPK activity in leptin-sensitive and -insensitive states, we examined phosphorylation of AMPK and its target, acetyl CoA carboxylase (ACC), in muscles from LepTg under dietary modification. Here we show that phosphorylation of AMPK and ACC are chronically augmented in LepTg soleus muscle, with a concomitant increase in the AMP-to-ATP ratio and a significant decrease in tissue triglyceride content. Despite preexisting hyperleptinemia, high-fat diet (HFD)-fed LepTg develop obesity, insulin-resistance, and hyperlipidemia. In parallel, elevated soleus AMPK and ACC phosphorylation in regular diet-fed LepTg is attenuated, and tissue triglyceride content is increased in those given HFD. Of note, substitution of HFD with regular diet causes a robust recovery of soleus AMPK and ACC phosphorylation in LepTg, with a higher rate of body weight reduction and a regain of insulin sensitivity. In conclusion, soleus AMPK and ACC phosphorylation in LepTg changes in parallel with its insulin sensitivity under dietary modification, suggesting a close association between skeletal muscle AMPK activity and sensitivity to leptin.
Solar cycle variations of modulation parameters are derived from cosmic-ray anisotropy observed by a network of multidirectional muon telescopes. The network covers wide ranges of median rigidity of ...primary cosmic-rays and effective latitude of viewing. It was found that the radial density gradient varies with a good correlation with the solar activity, while the parallel mean-free-path of the cosmic-ray diffusion varies with an anti-correlation with the solar activity. These features are both in accord with the conventional modulation theory incorporating convection and diffusion processes. The correlation coefficients of yearly mean values of radial density gradient and parallel mean-free-path with the sunspot number were respectively 0.7 and 0.6. The bi-directional latitudinal gradient showed a clear 22-year solar magnetic cycle as predicted by the drift model for the cosmic-ray transport in the heliosphere. The unidirectional latitudinal gradient, on the other hand, showed no clear variation related to the 11-year solar activity or 22-year solar magnetic-cycles, but it remains positive after the late 80's implying a higher density of cosmic-rays in the southern hemisphere below the heliospheric current sheet. We also analyze temporal variations of modulation parameters derived from neutron monitor observations at ∼10 GV. By comparing with those obtained from muon observations at 60 GV, we discuss the rigidity dependence of temporal variations of modulation parameters.
ABSTRACT A 100 m2 muon detector (MD) was successfully constructed under the existing Tibet air shower (AS) array in the late fall of 2007. The sensitivity of the Tibet AS array to cosmic gamma rays ...can be improved by selecting muon-poor events with the MD. Our MC simulation of the MD response reasonably agrees with the experimental data in terms of the charge distribution for one-muon events and the background rejection power. Using the data collected by the Tibet AS array and the 100 m2 MD taken from 2008 March to 2010 February, we search for continuous gamma-ray emission from the Crab Nebula above ∼100 TeV. No significant excess is found, and the most stringent upper limit is obtained above 140 TeV.
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