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Cosmogenic nuclides such as 14C from tree rings and 10Be and 36Cl from ice cores are excellent proxies for the past extremely large solar energetic particle (SEP) events, which are dozens of times larger than the largest SEP event in the history of observation. So far, several rapid 14C increases have been discovered, which are considered to have originated from extreme SEP events (or set of successive SEP events) from verifications using multiple cosmogenic nuclide analyses in natural archives. Although these events are characterized by a rapid increase in cosmogenic nuclide concentrations, 14C data recorded worldwide do not always show similar variations, especially during the 993 CE event, where a rapid increase was recorded in either 992–993 CE or 993–994 CE in several records. We present new 14C data of the Japanese cedar sample for the 993 CE event. Although the latest data show no significant increase in 1 year, an overall increase pattern is consistent with the previously reported 14C data of the Japanese cedar, which supports that a significant 14C increase occurred from 993 to 994 CE in the Japanese sample. Given the dominant 14C production in high latitudes by SEPs, the difference in timing of increase may be a transport effect in the atmosphere. Moreover, the difference in the timing of the 14C increase can cause a 1-year age-determination error using the 993 CE radiocarbon spike. Compared with the 14C data between tree samples from high latitude and midlatitude, including Japan, high-latitude data can capture 14C changes originating from SEP events more quickly and clearly and may be more suitable for a SEP event exploration in the past.

Silicon-based solid-state detectors (SSDs) are crucial for investigating the properties of superheavy elements (SHEs), since they measure the energy of SHEs and charged particles that are emitted as successive decay events of the SHEs. We have developed a segmented SSD for SHE studies using the new gas-filled recoil ion separators (GARIS-II and GARIS-III) at RIKEN. It is based on a back-illuminated Si PIN photodiode in which the irradiation is through the N+ layer. The detector is introduced as a side one for the GARIS focal plane detection system. To investigate the characteristics of the SSD, 241Am α particles were irradiated by automatically moving and rotating the α source for each segmented portion of the SSD. A Monte Carlo simulation was also performed to estimate the dead layer thickness of the segmented SSD.

Proxy-based observations of solar activity in the past have revealed long-term variations, such as the Gleissberg cycle (~88 yr), de Vries cycle (~200 yr), and the Hallstatt cycle (~2000 yr). Such long-term variations of solar activity sometimes cause the disappearance of sunspots for several decades. Currently, solar activity is becoming weaker, and there is a possibility that another long-term sunspot minimum could occur. However, the detailed mechanism of the weakening in solar activity is unknown, and the prediction of solar activity is ambiguous. In this study, we investigate the transitions of solar cycle length before the onset of the Spoerer Minimum, the longest grand minimum in the past 2000 yr. We measured the 14C content in an asunaro tree (Thujopsis dolabrata) excavated at Shimokita Peninsula from 1368–1420 CE using the compact AMS system at Yamagata University. It is found that the solar cycle lengthened to be 14–16 yr from 2 cycles before the onset of the Spoerer Minimum.

Atmospheric radiocarbon (14C) levels increased from 1955 to 1963 due to atmospheric nuclear weapon tests, and then decreased. As 14C accumulates in human tooth enamel while the enamel is being formed, 14C can be used to estimate the birth year of unidentified bodies. Measurement results of 14C content in tooth enamel using accelerator mass spectrometry vary depending on the enamel's sample site. To address this problem, a method for equalizing samples using a pulverizer was considered in this study. Regarding the tube and cone used as the pulverizer, (1) a polycarbonate tube and stainless steel cone, (2) a stainless steel tube and cone, and (3) a tungsten carbide tube and cone, were compared. In (1), the modern carbon ratio was approximately half that of the normal ratio of 100 pMC, with which accurate dating was impossible, and in (2), a high background value was obtained for IAEA-C1, which was pulverized using a reusable tube and cone. In (3), the 14C content for IAEA-C1 pulverized using reusable tube and cone, which was washed with quartz sand, was 0.31 ± 0.01 pMC. This result did not show any problems regarding background value. Therefore, the use of tungsten carbide products and washing with quartz sand is recommended for 14C measurement of pulverized teeth.

An accelerator mass spectrometry (AMS) system and an automated graphitization line were installed at Yamagata University (YU) in 2009. Approximately 2000 samples are measured per year using the YU-AMS system. The long-term stability of the system was assessed by measuring the standard sample IAEA-C7 graphitized by the automated graphitization line. In March 2014, a second automated graphitization line and an additional ion source for the YU-AMS system were installed to meet the requirement of 14C measurement for pharmacological and medical applications. A phosphoric acid treatment system was also developed for the radiocarbon dating of calcium carbonate (CaCO3) in shell and coral samples. Performance tests on the new YU-AMS system were carried out by measuring the C-series standard samples (C1-C9) and oxalic acid II (HOxII) obtained from IAEA and NIST, respectively. The results of the 14C concentration pMC are in good agreement with the consensus values. Performance tests for medical applications were also carried out by measuring the 14C concentration of 14C-glucose in human plasma.

The precise energy measurement of charged particles using a silicon semiconductor detector (SSD) is very important in studies of the characteristics of superheavy elements (SHEs). It is necessary to evaluate the dead layer thickness of the SSD to measure the recoil energy of charged particles, such as SHEs, and $\alpha$ particles or fission fragments that are emitted upon the successive decay from the SHEs. Since the energy resolution of the SSD depends on the thickness of the dead layer, a back-illuminated SSD with a thin dead layer has been introduced for SHE research. To evaluate the dead layer thickness of the SSD, energy spectra were first investigated by irradiating $^{241}$Am $\alpha$ particles at incident angles of 0$^\circ$ and 45$^\circ$ for two types of SSD. The dead layer thicknesses of the SSDs were deduced by a computer simulation using the particle and heavy ion transport code system (PHITS).

Rapid in situ formation of metal carbonyl complexes with short-lived nuclides has been demonstrated to be feasible with recoiling ions formed in nuclear fusion and fission reactions. These carbonyl complexes are highly volatile and can be transported rapidly in a gas-stream to counting or chemistry devices. This method was already successfully applied in the chemical investigation of the superheavy element seaborgium (Z = 106) and appears promising for various fields of nuclear research. In this article, we give an overview on the current status of metal carbonyl complex studies with short-lived d-element isotopes.

The exotic decay process of $\ensuremath{\beta}$-delayed fission ($\ensuremath{\beta}\mathrm{DF}$) has been studied in the neutron-deficient isotope $^{230}\mathrm{Am}$. The $^{230}\mathrm{Am}$ nuclei were produced in the complete fusion reaction $^{207}\mathrm{Pb}(^{27}\mathrm{Al},4n)^{230}\mathrm{Am}$ and separated by using the GARIS gas-filled recoil ion separator. A lower limit for the $\ensuremath{\beta}\mathrm{DF}$ probability ${P}_{\ensuremath{\beta}\text{DF}}(^{230}\mathrm{Am})g0.30$ was deduced, which so far is the highest value among all known $\ensuremath{\beta}\mathrm{DF}$ nuclei. The systematics of $\ensuremath{\beta}\mathrm{DF}$ in the region of $^{230}\mathrm{Am}$ will be discussed.

A new micromesh gas (Micromegas) detector has been developed for a gaseous photomultiplier tube (PMT) with a bialkali photocathode. A basic performance test of the Micromegas detector was carried out for a Ne (90%) + CF4 (10%) gas mixture using an X-ray beam. We constructed gaseous PMTs with a bialkali photocathode and Micromegas detectors. The photoelectron collection efficiencies in several gases and the suppression of ion feedback were investigated.

A new glass plate (GP) has been developed for a hole-type micropattern gas detector (MPGD). The material of the GP is a crystallized photosensitive etching glass (PEG3C) made by Hoya Corporation. A basic performance test of the hole-type MPGD was carried out using an X-ray beam with Ne-based gas mixtures at 1 atm. Gains of up to 5×10 3 and 6×10 4 were obtained using a single and a double GP, respectively. An energy resolution of 17% was obtained for 6 keV X-rays with a single GP. It was also shown that there is little charging-up effect in the GP. In this paper, we report the characteristics of the new hole-type MPGD with a GP made of PEG3C.

Objective The regulatory mechanisms responsible for acute exercise-induced expression of monocarboxylate transporters MCT1 and MCT4 mRNA in skeletal muscle remain unclear. 5′-adenosine-activated protein kinase (AMPK) is a key signaling molecule that regulates gene expression at the mRNA level. We examined whether AMPK activation is involved in acute exercise-induced expression of MCT1 and MCT4 mRNA in fast-twitch muscle. Materials/Methods Male Sprague–Dawley rats were subjected to an acute bout of either 5 min high-intensity intermittent swimming (HIS) or 6-h low-intensity prolonged swimming (LIS). The effects of acute exercise on the phosphorylation of AMPK (p-AMPK), calcium/calmodulin pendent kinase II (p-CaMKII), p38 mitogen-activated protein kinase (p-p38MAPK), and MCTs mRNA were analyzed in vivo. To observe the direct effects of AMPK activation on MCTs mRNA, the effects of 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), caffeine, and dantrolene were analyzed in vitro using an isolated muscle incubation model. Results The p-AMPK increased in response to both HIS and LIS, although the p-CaMKII and p-p38MAPK were increased only following HIS. Irrespective of exercise intensity, MCT1 and MCT4 mRNA was also transiently upregulated by both HIS and LIS. Direct exposure of the epitrochlearis muscle to 0.5 mmol/L AICAR or 1 mmol/L caffeine, which activated p-AMPK increased both MCT1 and MCT4 mRNA levels. When pAMPK was inhibited by dantrolene, neither MCT1 nor MCT4 mRNA was increased. Conclusion These results suggest that acute exercise-induced increases in MCT1 and MCT4 mRNA expression may be possibly mediated by AMPK activation, at least in part in fast-twitch muscle.

A new gas-filled recoil ion separator GARIS-II was on-line tested by using two 40Ar-induced fusion reactions of 169Tm(40Ar,4n)205Fr and 208Pb(40Ar,3n)245Fm, respectively. The products were collected to a focal plane with high efficiency of 47 ± 1 and 63 ± 9 % for 205Fr and 245Fm under low background condition.

A carbonyl compound that tips the scales Life is short for the heaviest elements. They emerge from high-energy nuclear collisions with scant time for detection before they break up into lighter atoms. Even et al. report that even a few seconds is long enough for carbon to bond to the 106th element, seaborgium (see the Perspective by Loveland). The authors used a custom apparatus to direct the freshly made atoms out of the hot collision environment and through a stream of carbon monoxide and helium. They compared the detected products with theoretical modeling results and conclude that hexacarbonyl Sg(CO) 6 was the most likely structural formula. Science , this issue p. 1491 ; see also p. 1451

The production of 283Cn in the hot fusion reaction of 238U(48Ca,3n) was confirmed using a new gas-filled recoil ion separator GARIS-II. At the excitation energies of the compound nucleus E* = 34.5 MeV, two decay events from 283Cn were observed, resulting in the cross section of \(\sigma _{3n} = 2.0_{ - 1.3}^{ + 2.7}\) pb. One is the spontaneous fission with decay time τ = 14.4 s. The other is the 9.45 MeV α-decay with τ = 5.4 s, followed by the spontaneous fission of 279Ds (154 ms).

RIKEN Nishina Center for Accelerator Based Science, Saitama 350-0198, Japan 1 Faculty of Science, Niigata University, Niigata 950-2181, Japan 2 Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan 3 Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan 4 Graduate School of Science and Engineering, Yamagata University, Yamagata 990-8560, Japan 5 Department of Physics, Saitama University, Saitama 338-8570, Japan E-mail: daiya@riken.jp

The fusion reaction 48Ca + 248Cm → 296Lv* was investigated using the gas-filled recoil ion separator GARIS at RIKEN. The reaction was studied at excitation energies of 41.3 and 38.2 MeV. A total of seven decay chains were observed. Three of the chains were assigned to the decay of 292Lv and three to the decay of 293Lv. A possible observation of an α-decay branch of 284Cn populating the new spontaneously fissioning nucleus 280Ds is discussed. The assignment of one of the decay chains to the 3n evaporation channel, resulting in a spontaneous fission branch of 285Cn, or to the 2n channel, resulting in the population of the new fissioning nucleus 286Cn, is ambiguous. Measured cross sections are in agreement with previously published values.

In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the investigation of fragile single molecular species by gas-phase chromatography. The latest success with the heaviest group 6 transactinide seaborgium is highlighted. The formation of a very volatile hexacarbonyl compound Sg(CO)6 was observed similarly to its lighter homologues molybdenum and tungsten. The interactions of these gaseous carbonyl complex compounds with quartz surfaces were investigated by thermochromatography. Second-generation experiments are under way to investigate the intramolecular bond between the central metal atom of the complexes and the ligands addressing the influence of relativistic effects in the heaviest compounds. Our contribution comprises some aspects of the ongoing challenging experiments as well as an outlook towards other interesting compounds related to volatile complex compounds in the gas phase.

The production and decay properties of an isotope of the 112th element, 277Cn, were investigated using a gas-filled recoil ion separator by irradiation of 208Pb targets with 70Zn beams at 347.5, 351.5, and 355.5 MeV. The excitation function for this reaction was measured for the first time. We observed one decay event assigned to the decay of 277Cn at the beam energy of 351.5 MeV. The measured production cross section was 0.078+0.179 pb. The present result gives improved half-lives of 0.61+0.46 and 0.19+0.14 ms for 277Cn and 273Ds, respectively. At the other energies, no event was observed. The measured upper cross section limits were 0.25 and 0.15 pb at the beam energies of 347.5 and 355.5 MeV, respectively.

An isotope of the 113th element, i.e., 278[113], was produced in a nuclear reaction with a 70Zn beam on a 209Bi target. We observed six consecutive {\alpha}-decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector under an extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of 262Db and 258Lr in both decay energies and decay times. This indicates that the present decay chain consisted of 278[113], 274Rg (Z=111), 270Mt (Z=109), 266Bh (Z=107), 262Db (Z=105), and 258Lr (Z=103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads to the unambiguous production and identification of the isotope 278[113] of the 113th element., Comment: http://jpsj.ipap.jp/link?JPSJ/81/103201/