Review on Morphological Insights of Self-Potential Anomalies on Volcanoes

Energy and thermal transfers in active volcanoes can play an important role incontrolling their dynamics depending on the hydrothermal state. Much geothermalenergy is released through the groundwater circulation, hot gas emission and thermalconduction. Therefore, it is very important to know the hydrological and thermalenvironments associated with volcanoes from the volcano-energetic point of view.However, it is difficult to evaluate these because of the availability of only a fewborehole data on the summit of volcanoes. Recent studies reveal that self-potential(SP) anomalies (up to some hundreds of mV) are observed on volcanoes, activefissure zones and/or fumarolic areas, suggesting that the SP anomalies are closelyrelated to heat-triggered phenomena such as thermoelectric and electrokinetic effectsdue to hydrothermal circulations. Therefore, SP studies can be appropriate for sensingthe thermal and hydrothermal states of volcanoes. In addition, monitoring SP anomaliescan be an efficient method for describing the change of thermal state and the evolutionof the hydrothermal (and volcanic) activities.In this paper, we have reviewed the origin of the SP anomalies associated withvolcanic phenomena theoretically as well as experimentally. Subsequently, wehave presented the results of many case studies and have classified the types ofanomalies in accordance with possible mechanisms. We have also described theresults of time variations of SP anomalies associated with volcanic activities. Timevarying SP fields exhibit the dynamic aspects of volcanic activities correspondingto the evolution of hydrothermal activity, changes in ground water circulation andmagma displacement. These morphological insights should lead to a quantitativeinterpretation of SP anomalies in volcanic regions.     

Determination of silicate in seawater by inductively Coupled Plasma Atomic Emission Spectrometry

Inductively Coupled Plasma Atomic Emission Spectrometry (ICP) was adopted for direct analysis of silicate in seawater, eliminating necessity for pre-treatment. Via this method, the determination of silicate is rapid and easy compared with conventional methods of colorimetry. In seawater analysis, a decrease of sensitivity of about 24% was observed due to interference by coexisting elements, mainly Na. Examination of the analytical conditions revealed a detection limit of 0.3 M Si, and precisions of approximately 3.2, 2.0 and 1.3% for Si levels of 4, 15 and 94 M, respectively. Using this method, silicate determination in the East China Sea was attempted.     

The diet of mesopelagic fish from the Pacific coast of Hokkaido,Japan

The diet of at least 28 species of mesopelagic fish from the Pacific coast of Hokkaido was examined. The dominant family was the Gonostomatidae (42%) which was represented by five species. The most abundant species wasCyclothone atraria which together with the other species of this genus preyed predominantly on copepods. Euphausiids and copepods were dominant in the diet ofGonostoma gracile. The next most abundant family was the Myctophidae (32%) which was represented by seven species. The dominant species,Stenobrachius nannochir, preyed mainly on copepods. Copepods were also the dominant food item of the other myctophids except forLampanyctus jordani which fed mainly on euphausiids. The other important family was the Bathylagidae (21%).Leuroglossus schmidti was the dominant species and its diet was more diverse with ostracods, copepods, molluscs and larvaceans being the most important food items.Bathylagus ochotensis had a similar diet. Copepods were the most important food items for all but a few species and their occurrence in the fish stomachs was related to the known vertical distribution of both predators and prey. Ostracods and euphausiids were also important prey items, the latter especially in large fish species. Molluscs and larvaceans were restricted to the two species of the family Bathylagidae.     

Measurements of the Turbulent Energy Dissipation Rate around the Shelf Break in the East China Sea

Using the micro-structure profiler, TurboMAP, large values for the turbulent energy dissipation rate ε were found just above the bottom of the shelf and around the thermocline near the continental shelf break in the East China Sea. The values found above the bottom are produced by the bottom stress due to tidal currents, resulting in a distinct bottom mixed layer where the vertical eddy diffusivity Kz is also large. Distinct maxima in the values of ε detected around the thermocline are located at the depth of the fine-scale shear maxima detected with the moored ADCP. The vertical profiles of ε were compared with those of the current velocity, and it was found that the maxima in ε appear to correspond to those of the shear with fine scale. The magnitude of the observed ε coincided approximately with the ε calculated from the fine-scale shear and the buoyancy frequency according to the parameterization proposed by Gregg (1989), if the large-scale mean shear caused by the Kuroshio is subtracted. However, it is not clear whether the parameterization for the internal wave fields in the open ocean is applicable to the estimation of ε in the shelf break. Whereas the most predominant value of ε was found just above the bottom and around the thermocline, the maxima of ε could be found in the internal area. They could have been caused by the propagation of the vertically high wave number internal tides along the characteristic ray.     

基于地震“哼鸣”的全球面波层析成像

基于地震的全球面波层析成像技术的发展对于探测地球深部动力学状态起着至关紧要的作用。人们很自然地认为只有大地震才会产生类似探测所需要的穿入地球深部的长周期地震波。然而,由海洋和/或大气扰动随机产生的地震＂哼鸣＂的发现,即地球背景自由振荡,提供了一种可供选择的方法。我们在此呈现的是利用地震＂哼鸣＂而非天然地震进行上地幔地震层析成像的结果。在100～400s周期,Rayleigh波的相速度异常可通过下述方式测得,即对观测得到的54个遍布全球的地震台站中每两个台站间的互相关函数进行模拟,然后对这些异常进行反演,以获取上地幔三维S波速度结构。此方法为探测具有大气和/或海洋的类地行星——特别是火星的三维内部结构提供了一种新的途径。     

Does heavy oil pollution induce bacterial diseases in Japanese flounder Paralichthys olivaceus?

As basic research for the effect of heavy oil on the fish immune system, in this study, the number of leukocyte was counted in Japanese flounder Paralichthys olivaceus, after exposure to heavy oil at a concentration of 30 g/8 L for 3 days. To compare the numbers of bacteria in the skin mucus between oil-exposed and control fish, viable bacteria were enumerated by counting colony forming unit (CFU). Compared with 5.79 ± 1.88 × 10⁷ leukocytes/mL in the controls, the exposed fish demonstrated higher counts, averaging 1.45 ± 0.45 × 10⁸ cells/mL. The bacterial numbers of control fish were 4.27 ± 3.68 × 10⁴ CFU/g, whereas they were 4.58 ± 1.63 × 10⁵ CFU/g in the exposed fish. The results suggest that immune suppression of the fish occurred due to heavy oil stressor, and bacteria could invade in the mucus, resulting in the increasing leukocyte number to prevent infectious disease.     

Toxicogenomic analysis of immune system-related genes in Japanese flounder (Paralichthys olivaceus) exposed to heavy oil

Heavy oil contamination is one of the most important environmental issues. Toxicities of polycyclic aromatic hydrocarbons (PAHs), including immune toxicities, are well characterized, however, the immune toxic effects of heavy oil, as a complex mixture of PAHs, have not been investigated. In the present study, we selected Japanese flounder (Paralichthys olivaceus) as a model organism, and observed alteration of immune function by the exposure to heavy oil. To analyze the expression profiles of immune system-related genes, we selected 309 cDNAs from our flounder EST library, and spotted them on a glass slide. Using this cDNA array, alteration of gene expression profiles was analyzed in the kidneys of flounders exposed to heavy oil. Six Japanese flounders (mean body weight: 197 g) were acclimated to laboratory conditions at 19–20 °C. Three fish were exposed to heavy oil C (bunker C) at a concentration of 3.8 g/L for 3 days, and the others were kept in seawater without heavy oil and used as the control. After the exposure period, the fish were transferred into control seawater and maintained for 4 days, and then they were dissected and their kidneys were removed. Total RNA was extracted from the kidney samples to use in gene expression analyses. The microarray detected alteration of immune system-related genes in the kidneys of heavy oil-exposed flounders, including down-regulation of immunoglobulin light chain, CD45, major histocompatibility complex class II antigens and macrophage colony-stimulating factor precursor, and up-regulation of interleukin-8 and lysozyme. These results suggest that pathogen resistance may be weakened in heavy oil-exposed fish, causing a subsequent bacterial infection, and then proinflammatory genes may be induced as a defensive response against the infection. Additionally, we found candidate genes for use as biomarkers of heavy oil exposure, such as N-myc downstream regulated gene 1 and heat shock cognate 71 kDa proteins.     

Pyrene induces a reduction in midbrain size and abnormal swimming behavior in early-hatched pufferfish larvae

Spills of heavy oil (HO) have an adverse effect on marine life. We have demonstrated previously that exposure to HO by fertilized eggs of the pufferfish (Takifugu rubripes) induces neural disruption and behavioral abnormality in early-hatched larvae. Here, two kinds of polycyclic aromatic hydrocarbons, pyrene and phenanthrene, were selected to examine their toxic effects on larval behavior of another pufferfish species (T. niphobles). Larvae exposed to pyrene or phenanthrene exhibited no abnormalities in morphology. However, those exposed to pyrene but not phenanthrene swam in an uncoordinated manner, although their swimming distance and speed were normal. The optic tectum, a part of the midbrain, of pyrene-exposed larvae did not grow to full size. Thus, these findings are indicated that pyrene might be a contributor to the behavioral and neuro-developmental toxicity, although there is no indication that it is the only compound participating in the toxicity of the heavy oil mixture.     

Vertical and horizontal distribution of fluorescent dissolved organic matter in the Southern Ocean

The vertical and horizontal distribution of fluorescent dissolved organic matter (FDOM), determined by fluorescence intensity at 320 nm excitation and 420 nm emission, were clarified in nine stations on two transects at the Southern Ocean, including a subtropical, subantarctic, polar frontal and Antarctic zone. All vertical profiles of fluorescence intensity showed that levels were lowest in the surface waters, increased with increasing the depth in mid-depth waters ( 2000 m), and then stayed within a relatively narrow range from there to the bottom. Such vertical profiles of FDOM were similar to those of nutrients, but were adverse to dissolved oxygen. In water columns below the temperature-minimum subsurface water (dichothermal waters) in the Antarctic zone and below the winter mixed layer in the other zones, we determined the relationships of fluorescence intensity to concentrations of nutrients and apparent oxygen utilization (AOU) over the entire area of the present study, and found significant linear correlations between the levels of fluorescence intensity and nutrient concentrations (r =  0.70 and 0.71 for phosphate and nitrate + nitrite, respectively) and AOU (r = 0.91). From the strong correlation coefficient between fluorescence intensity and AOU, we concluded that FDOM in the Southern Ocean is formed in situ via the biological oxidation of organic matter. The regeneration of the nutrients/consumption of the oxygen/formation of FDOM was active in mid-depth waters. However, the correlations between fluorescence intensities and nutrients and AOU were different in the mid-depth water masses, Subantarctic Mode Water (SAMW), and Antarctic Intermediate Water (AAIW), indicating that the sources of organic matter responsible for FDOM formation were different. A considerable amount of FDOM in the SAMW is thought to be produced by the remineralization of DOM in addition to sinking particulate organic matter, while DOM is less responsible for FDOM formation in the AAIW.     

Prediction of earthquake energy input from smoothed fourier amplitude spectrum

This paper attempts to show analytically that the energy-input spectra of damped SDOF systems and undamped MDOF systems excited by an earthquake motion can be predicted by smoothing the Fourier amplitude spectrum of the base acceleration. The spectral window for smoothing in the frequency domain for a damped SDOF system is identical with the probability density function of the time-variant or instantaneous vibration frequency resulting from non-linear hysteresis. The spectral window for an undamped MDOF system is identical with the set of squared participation factors associated with vibration modes. It was found that the increase in damping factor and the increase in participation of higher modes provide wider spectral windows, resulting in more flattened or unaltered energy-input spectra due to enhanced smoothing effects.