Heat balance of the surface layer of the sea at ocean weather station T

Heat balance of the upper 200 m of the sea south of Japan is studied, by the use of marine meteorological and oceanographic data at Ocean Weather Station T (29°N, 135°E), intensively obtained from June 1950 to November 1953. Local time change of the heat content in the surface layer and the net heat flux through the air-sea interface are calculated directly from these data, and the heat convergence in the sea is estimated from their residuals. Regarding the relative importance of one- and three-dimensional processes, it is found that, on a time scale of a few days to one month, the variation of heat content depends on heat convergence in the sea, while on a seasonal time scale, the heat content is determined primarily by the heat flux through the sea surface in December through February, by heat convergence within the sea from March to May, and by both processes from June to November. It is inferred that the heat convergence in the sea is caused by advection of water masses which are bounded by sharp fronts. Spectral analysis of sea surface temperature indicates that they typically take 2 to 3 days to pass the station, and their typical size is estimated as around 20 km by assuming the typical advection velocity of water masses to be 10 cm s^?1.     

Transposable genetic elements inSpirulina and potential applications for genetic engineering

Transposable elements in cyanobacteria are briefly reviewed. Evidence is presented to show that transposable elements inSpirulina platensis is actually reflected on the phenotype change, i e., helical to straight filaments. Transposition intermediates of DNA were isolated from the extrachromosome and the transposition was related to helical variations inSpirulina. Uses of transposable elements for microalgal recombination are discussed based on the transposition mechanism.

     

A practical model to estimate photosynthetically active radiation using general meteorological elements in a temperate humid area and comparison among models

Although accurately evaluating photosynthetically active radiation is important, much effort is required to measure this radiation using a quantum sensor. We develop a new model that makes estimates using only general meteorological data—solar radiation, atmospheric pressure, air temperature, and relative humidity. Root mean square deviations for eight datasets at five sites in Japan were smaller than 5.2 %, similar to error in other studies and to individual differences of quantum sensors. Most root mean square deviations of nine previous models and our eight datasets are larger than that of the new estimation model, which performed well. This suggests that the model is useful for estimating photosynthetically active radiation in a temperate, humid area of Japan.     

Permian Peri‐glacial Deposits from Central Mongolia in Central Asian Orogenic Belt: A Possible Indicator of the Capitanian Cooling Event

A dropstone‐bearing, Middle Permian to Early Triassic peri‐glacial sedimentary unit was first discovered from the Khangai–Khentei Belt in Mongolia, Central Asian Orogenic Belt. The unit, Urmegtei Formation, is assumed to cover the early Carboniferous Khangai–Khentei accretionary complex, and is an upward‐fining sequence, consisting of conglomerates, sandstones, and varved sandstone and mudstone beds with granite dropstones in ascending order. The formation was cut by a felsic dike, and was deformed and metamorphosed together with the felsic dike. An undeformed porphyritic granite batholith finally cut all the deformed and metamorphosed rocks. LA‐ICP‐MS, U–Pb zircon dating has revealed the following ²⁰⁶Pb/²³⁸U weighted mean igneous ages: (i) a granite dropstone in the Urmegtei Formation is 273 ± 5 Ma (Kungurian of Early Permian); (ii) the deformed felsic dike is 247 ± 4 Ma (Olenekian of Early Triassic); and (iii) the undeformed granite batholith is 218 ± 9 Ma (Carnian of Late Triassic). From these data, the age of sedimentation of the Urmegtei Formation is constrained between the Kungurian and the Olenekian (273–247 Ma), and the age of deformation and metamorphism is constrained between the Olenekian and the Carnian (247–218 Ma). In Permian and Triassic times, the global climate was in a warming trend from the Serpukhovian (early Late Carboniferous) to the Kungurian long and severe cool mode (328–271 Ma) to the Roadian to Bajocian (Middle Jurassic) warm mode (271–168 Ma), with an interruption with the Capitanian Kamura cooling event (266–260 Ma). The dropstone‐bearing strata of the Urmegtei Formation, together with the glacier‐related deposits in the Verkhoyansk, Kolyma, and Omolon areas of northeastern Siberia (said to be of Middle to Late Permian age), must be products of the Capitanian cooling event. Although further study is needed, the dropstone‐bearing strata we found can be explained in two ways: (i) the Urmegtei Formation is an autochthonous formation indicating a short‐term expansion of land glacier to the central part of Siberia in Capitanian age; or (ii) the Urmegtei Formation was deposited in or around a limited ice‐covered continent in northeast Siberia in the Capitanian and was displaced to the present position by the Carnian.     

Diversity of Pliocene mysticetes from eastern Japan

Abstract Assemblages of Early Pliocene Mysticeti (Cetacea) from the Sendai-Iwate and Choshi areas in eastern Japan were examined. The early Early Pliocene Tatsunokuchi and Yushima formations of the Sendai-Iwate area have yielded many cetotheres assigned to Herpetocetus (Cetotheriidae) and some extinct rorquals assigned to Burtinopsis (Balaenopteridae) and other genera. The late Early Pliocene strata of the Na-arai Formation of the Choshi area has yielded more than 300 mysticete ear bones which fall into seven morphotypes. Assemblages from the two areas differ greatly in taxonomic composition. Archaic mysticetes are dominant in the Sendai-Iwate area, while modern mysticetes are dominant and diverse in the Choshi area. Based on the results of this study we conclude that the diversity of the Early Pliocene mysticetes in the western North Pacific is comparable to that of the Recent.     

A list of fossil cetaceans in Japan

Abstract Fossil cetacea of Japan are abundant and diverse. Despite several summary articles, all the known taxa have not previously been compiled in one place. Here we present a list of the published fossil cetacean records from the Japanese archipelago. The record extends from Middle or Late Oligocene to the Holocene, and includes representatives of both the suborders Odontoceti and Mysticeti. No Eocene Cetacea or Archaeoceti are recorded from Japan. As is typical of the eastern North Pacific and the South Pacific, the Oligocene and Early Miocene assemblages are comprised of archaic and usually extinct families, and the younger assemblages are represented by modern groups comprised of extant genera and families.     

Shaking table tests of steel frame with superelastic Cu–Al–Mn SMA tension braces

Shaking table tests are performed on a one‐bay one‐story steel frame with superelastic Cu–Al–Mn shape memory alloy (SMA) tension braces. The frame is subjected to a series of scaled ground motions recorded during the 1995 Kobe earthquake, Japan. The test results demonstrate that the SMA braces are effective to prevent residual deformations and pinching. It is also shown that the time history responses observed from the shaking table tests agree well with the numerical predictions using a rate‐independent piecewise‐linear constitutive model calibrated to the quasi‐static component tests of the SMA braces. This suggests that the loading rate dependence of Cu–Al–Mn SMAs as well as the modeling error due to the piecewise linear approximation can be neglected in capturing the global response of the steel frame. Numerical simulations under a suite of near‐fault ground motion records are further performed using the calibrated analytical models to demonstrate the effectiveness of the SMA braces when the variability of near‐fault ground motions is taken into account. A stopper, or a deformation restraining device, is also proposed to prevent premature fracture of SMA bars in unexpectedly large ground motions while keeping the self‐centering capability in moderate to large ground motions. The effectiveness of the stopper is also demonstrated in the quasi‐static component and shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd.     

A heating process of Kuchi-erabu-jima volcano,Japan, as inferred from geomagnetic field variations and electrical structure

Since August 2000, we have recorded the total intensity of the geomagnetic field at the summit area of Kuchi-erabu-jima volcano, where phreatic eruptions have repeatedly occurred. A time series analysis has shown that the variations in the geomagnetic field since 2001 have a strong relationship to an increase in volcanic activity. These variations indicate thermal demagnetization of the subsurface around the presently active crater. The demagnetization source for the early variations, until summer 2002, was estimated at about 200 m below sea level. For the variations since 2003, the source was modeled on the basis of the expansion of a uniformly magnetized ellipsoid. The modeling result showed that the source is located at 300 m above sea level beneath the crater. We carried out an audio-frequency magnetotelluric survey with the aim of obtaining a relation between the demagnetization source and the shallow structure of the volcano. A two-dimensional inversion applied to the data detected two good conductors, a shallow thin one which is restricted to a region around the summit area, while the other extends over the edifice at depths between 200 and 800 m. These conductors are regarded as clay-rich layers with low permeability, which were assumed to be generated through hydrothermal alteration. The demagnetization source for the early variations was possibly located at the lower part of the deep conductor and the source after 2003 lies between the two conductors, where groundwater is considered to be abundant. Based on these results, as well as on seismological, geodetic, and geochemical information, we propose a heating process of the Kuchi-erabu-jima volcano. In the initial stage, high-temperature volcanic gases supplied from the deep-seated magma remained temporarily at the level around the lower part of the less permeable deep conductor since the ascent path had not yet been established. Then, when the pathway developed as a result of repeated earthquakes, it became possible for a massive flux of volcanic gases to ascend through the conductor. The high temperature gases reached the aquifer located above the conductor and the heat was efficiently transported to the surrounding rocks through the groundwater. As a consequence, an abrupt increase of the gas flux and diffusion of the heat through the aquifer occurred and the high-temperature zone expanded. Since the high-temperature zone is located beneath another conductor, which acts as caprock, we assume that the energy of the phreatic explosion is accumulated there.