DGPS and RTK Positioning Using the Internet

The Internet as a basis for Real-Time Kinematic (RTK) and differential Global Positioning System (DGPS) service provides many advantages for worldwide GPS users. Among these advantages are service unification, open architecture, bidirectional communication, and scalability. The current development of this service allows users to use RTK and DGPS through the Internet with conventional accuracy over the short and medium baselines. The perspective for this service lies in the field of wide-area augmentation systems (WASS). At this stage of the Internet-based RTK and DGPS service project, the general concept, system components, draft standards, and software are developed. ? 2000 John Wiley & Sons, Inc.     

Distribution of moon jellyfish Aurelia aurita in relation to summer hypoxia in Hiroshima Bay,Seto Inland Sea

Biological and physical surveys were conducted in order to investigate the relationship between environmental conditions and the distribution of moon jellyfish Aurelia aurita in Hiroshima Bay, western Seto Inland Sea, Japan. Moon jellyfish and ichthyoplankton were collected at 13 stations in Hiroshima Bay during monthly surveys from July to September in 2006 and 2007. Surface temperature in 2006 was significantly lower during the August and September cruises and surface salinity was lower during all cruises than in 2007. Moon jellyfish was the most dominant gelatinous plankton collected, accounting for 89.7% in wet weight. Mean moon jellyfish abundance in 2006 was higher than that in 2007 from July through September, with significant inter-year differences for July and September. Variability in precipitation and nutritional input from the Ohta River, northernmost part of Hiroshima Bay, were suggested as possible factors affecting the inter-annual variability in moon jellyfish abundance in the coastal areas of northern Hiroshima Bay. Moon jellyfish were more abundant in the coastal areas of northern Hiroshima Bay, where the dissolved oxygen (DO) concentration was lower, while low in the central part of the bay. Japanese anchovy Engraulis japonicus eggs were most dominant (58.1% in number) among the ichthyoplankton and were abundant in the central area of Hiroshima Bay. Explanatory analysis was conducted to detect possible effects of environmental conditions on the abundance of moon jellyfish and Japanese anchovy eggs during the summer months in Hiroshima Bay. Of the environmental conditions tested (temperature, salinity and DO of surface and bottom layers at each sampling station), bottom DO had the most significant effect on the moon jellyfish abundance: there was a negative correlation between the bottom DO and the moon jellyfish abundance in Hiroshima Bay during summer.     

Molecular cloning and mRNA expression of cytochrome P4501A1 and 1A2 in the liver of common minke whales (Balaenoptera acutorostrata)

This study presents full-length cDNA sequences of CYP1A1 and 1A2, in common minke whale (Balaenoptera acutorostrata) from the North Pacific. Both CYP1A1 and CYP1A2 cDNAs had an open reading frame of 516 amino acid residues, and predicted molecular masses were 58.3 kDa and 58.1 kDa, respectively. The deduced full-length amino acid sequence of CYP1A1 revealed higher identities with those of sheep (86%) and pig (87%), and that of CYP1A2 was most closely related to human (82%) and monkey CYP1A2 (82%) among species from which CYP1A2 has been isolated so far. Differences in certain conserved and functional amino acid residues of CYP1A1 and 1A2 between common minke whale and other mammalian species indicate the possibility of their specific metabolic function. Concentrations of organochlorine compounds (OCs) including PCBs and DDTs analyzed in common minke whale liver showed no significant correlation with hepatic mRNA expression levels of CYP1A1 and CYP1A2, indicating no induction of these enzymes by such OCs.     

Occurrence of 3-hydroxy acids in microalgae and cyanobacteria and their geochemical significance

3-Hydroxy acids were detected in pure cultured microalgae: Chlorophyta—Chlamydomonas reinhardtii and Chlorella pyrenoidosa and Rhodophyta—Cyanidium caldarium (two strains), and cyanobacteria (Cyanophyta)—Anacystis nidulans, Phormidium foveolarum, Anabaena variabilis and Oscillatoria sp. Normal and branched (iso and anteiso) 3-hydroxy acids in the ranges of C₈-C₂₆ were found in all the samples studied at concentrations ranging from 0.036 to 2.3 and 0.000 to 0.12 mg g^?1 of dry sample, respectively. The major constituents were generally even-carbon numbered normal acids with carbon chain lengths below C₂₀. Microalgae and cyanobacteria may be the important sources of 3-hydroxy acids in natural environments.     

U–Pb zircon geochronology of the North Pole Dome adamellite in the eastern Pilbara Craton

Supracrustal rocks around the North Pole Dome area, Western Australia, provide valuable information regarding early records of the evolution of crustal processes, surface environments, and biosphere. Owing to the occurrence of the oldest known microfossils, the successions at the North Pole Dome area have attracted interest from many researchers. The Paleoarchean successions (Warrawoona Group) mainly comprise mafic‐ultramafic greenstones with intercalated cherts and felsic lavas. Age constraints on the sediments have been mainly based on zircon U–Pb geochronology. However, many zircon grains have suffered from metamictization and contain anomalously high contents of common Pb, which makes interpretation of the U–Pb data complicated. In order to provide more convincing chronological constraints, an U–Pb Concordia age is widely accepted as the best estimate. Most zircons separated from two adamellites also suffered from severe metamictization. In our analyses, less metamictized domains were selected using a pre‐ablation technique in conjunction with elemental mapping, and then their U–Pb isotopic compositions were determined with a laser ablation inductively coupled plasma mass spectrometry. Most analyzed domains contained certain amounts of common Pb (²⁰⁴Pb/²⁰⁶Pb > 0.000 1), whereas three and five U–Pb data points with less common Pb (²⁰⁴Pb/²⁰⁶Pb < 0.000 1) were obtained. These U–Pb datasets yielded U–Pb Concordia ages of ca 3 445 Ma and 3 454 Ma, respectively. These ages represent the timing of the adamellite intrusion, and constrain the minimum depositional age of the Warrawoona Group. In addition, a single xenocrystic zircon grain showed a ²⁰⁷Pb/²⁰⁶Pb age of ca 3 545 Ma, supporting the idea that the sialic basement of the Pilbara Craton existed prior to 3 500 Ma. The in situ U–Pb zircon dating combined with the pre‐ablation technique has the potentials to identify non‐metamictized parts and to yield precise and accurate geochronological data even from partially metamictized zircons.     

A dataset of continental river discharge based on JRA-55 for use in a global ocean circulation model

A dataset of historical river discharge into oceans was created using the CaMa-Flood global river routing model and adjusted runoff from the land component of JRA-55. The major rivers were well resolved with a 0.25° horizontal resolution. The total runoff on each drainage basin exhibits a distinctive bias on decadal time scales. The input runoff data were modified using 5-year low-pass-filtered multiplicative factors to fit the annual mean climatology and decadal variations in the reference dataset. The model incorporated data from 1958 to 2016. The yearly and seasonal variations of the major rivers are well represented by the model.     

Modeling of the branches of the Tsushima Warm Current in the Eastern Japan Sea

The branches of the Tsushima Warm Current (TWC) are realistically reproduced using a three-dimensional ocean general circulation model (OGCM). Simulated structures of the First Branch and the Second Branch of the TWC (FBTWC and SBTWC) in the eastern Japan Sea are mainly addressed in this study, being compared with measurement in the period September–October 2000. This is the first numerical experiment so far in which the OGCM is laterally exerted by real volume transports measured by acoustic Doppler current profiler (ADCP) through the Tsushima Straits and the Tsugaru Strait. In addition, sea level variation measured by tide-stations along the Japanese coast as well as satellite altimeters is assimilated into the OGCM through a sequential data assimilation method. It is demonstrated that the assimilation of sea level variation at the coastal tide-stations is useful in reproducing oceanic conditions in the nearshore region. We also examine the seasonal variation of the branches of the TWC in the eastern Japan Sea in 2000. It is suggested as a consequence that the FBTWC is continuous along northwestern Honshu Island in summertime, while it degenerates along the coast between the Sado Strait and the Oga Peninsula in other seasons. On the other hand, a mainstream of the SBTWC exists with meanders and eddies in the offshore region deeper than 1000 m to the north of the Sado Island throughout the year.     

HI Column Density Oscillation in Interstellar Space

The author proposes the possibility to observe the HI column density oscillation in small scales (∼ AU-scale). If such variance of the column density were to be observed, he would suggest that the observational results show the existence of some type of waves in two-phase gas mixture. Such wave is known to be a void wave in the context of multi-phase fluid dynamics. If the variation of HI column density is representation of the void wave, we can also expect the HII density variations have anti-correlation to the HI density fluctuations, in the context of classical two phase model of interstellar medium. This revised version was published online in July 2006 with corrections to the Cover Date.     

Merged binary white dwarf evolution: rapidly accreting carbon–oxygen white dwarfs and the progeny of extreme helium stars

We have examined the evolution of merged low-mass double white dwarfs that become luminous helium stars. We have approximated the merging process by the rapid accretion of matter, consisting mostly of helium, on to a carbon–oxygen (CO) white dwarf. After a certain mass is accumulated, a helium shell flash occurs, the radius and luminosity increase and the star becomes a yellow giant. Mass accretion is stopped artificially when the total mass reaches a pre-determined value. When the mass above the helium-burning shell becomes small enough, the star evolves blueward almost horizontally in the Hertzsprung–Russell diagram. The theoretical models for the merger of a 0.6-M_⊙ CO white dwarf with a 0.3-M_⊙ He white dwarf agree very well with the observed locations of extreme helium stars in the  log  T _eff–log  g   diagram, with their observed rates of blueward evolution, and with luminosities and masses obtained from their pulsations. Together with predicted merger rates for  CO+He  white dwarf pairs, the evolutionary time-scales are roughly consistent with the observed numbers of extreme helium stars. Predicted surface carbon and oxygen abundances can be consistent with the observed values if carbon and oxygen produced in the helium shell during a previous asymptotic giant branch phase are assumed to exist in the helium zone of the initial CO white dwarfs. These results establish the  CO+He  white dwarf merger as the best, if not only, viable model for the creation of extreme helium stars and, by association, the majority of R Coronae Borealis stars.