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The Early Cretaceous Ontong Java Plateau (OJP) in the southwestern Pacific Ocean is the largest oceanic plateau by volume on Earth, and a broad range of observations has been conducted to reveal its formation and evolution. However, because seafloor seismic observations of the OJP and surrounding areas have been insufficient so far, such experiments are capable of generating additional information regarding the crustal and mantle structure of the OJP. To image seismic velocity discontinuities from the crust to the uppermost mantle, we applied receiver function analysis to seismic records acquired by 17 broadband ocean bottom seismometers deployed across the region in and around the OJP and 3 broadband stations located on ocean islands in Micronesia (one: permanent, two: temporary). The results revealed midcrustal discontinuities and the Moho at depths of 10–20 and 30–40 km (from the top of the basement), respectively, in the central OJP. Moreover, a mantle discontinuity was also imaged at the depth of 55–60 km (from the top of the basement) in the central OJP. These boundaries were not imaged outside the OJP, implying that they are characteristic features of the OJP. In addition, receiver function images showed Moho signals at the depth of 20 km in the eastern OJP, where few previous seismic exploration surveys have been conducted. This depth is comparable with that found in the Manihiki and Hikurangi Plateaus that were potentially separated from the OJP. Key Points: We produced receiver function images of crustal and uppermost mantle structure beneath the Ontong Java Plateau (OJP)Multiple seismic discontinuities of the midcrust (10–20‐km depth) and Moho (30–40‐km depth) were imaged in the central OJPA horizontal seismic discontinuity was imaged in the mantle 57–63 km below sea level in the central OJP [ABSTRACT FROM AUTHOR]

Barotropic tidal currents over bottom topography force density surfaces to oscillate vertically and thereby to act as quasi‐stationary internal tide sources. Deploying a seafloor pressure gauge array with an aperture of 30 km for a year (2014–2015), we detected the low‐mode semidiurnal internal tidal waves propagating with a horizontal phase speed of ~1 m/s in the onshore and offshore directions over the array along the eastern slope of Aogashima Island, south of Japan. The amplitudes of the offshore propagating waves were greater than those of the onshore propagating waves, and both were positively correlated with the amplitudes of the local semidiurnal tide, which peaked in September and March. A tide‐resolving ocean circulation model (JCOPE‐T) well reproduced the observed onshore and offshore internal tidal wave propagation. The model indicated a standing wave region on the slope, where offshore propagating waves interact with standing waves locally pinned to the slope. Along the same profile over a distance of 100 km, we conducted seismic‐oceanographic analysis of the legacy multichannel seismic reflection data to retrieve vertical cross sections of the reflecting layers, which indicated sharp temperature changes in the ocean. Many of the slant reflecting layers were subparallel to the contour lines of the semidiurnal internal‐tide‐associated temperature anomalies in the JCOPE‐T model, suggesting a causal link between the fine reflection layering structure and the semidiurnal low‐mode internal tidal field. Plain Language Summary: Internal tidal waves are generated in the ocean by interactions between surface tides and the bottom topography. Their amplitudes are less than a few centimeters at the sea surface but can be more than a few tens of meters within the ocean. These waves play important roles in tidal dissipation, ocean mixing, hydroacoustic transmission, and submersible technology. Thus far, observations of internal tides have mainly been made from above by satellite altimetry and through ocean columns by cable mooring. In this report, we show that a pressure gauge array at the bottom of the ocean is a promising tool for detecting internal tides and constraining their generation mechanisms. We incorporated a tide‐resolving ocean circulation model that could simulate bottom pressure variations at the same locations in the same period as that during which the observations were made so that the same analyses could be performed for both the observed and simulated data. Remarkable agreement was found between the observed and simulated internal tidal signals. Concurrent simulation of ocean circulation with tides is useful for interpreting not only the array records of ocean bottom pressure gauges but also vertical cross‐sectional images of ocean acoustic reflections obtained using a seismic–oceanographic technique. Key Points: We detected partly standing semidiurnal internal tides on the eastern slope of the Izu‐Bonin ridge using a seafloor pressure gauge arrayA tide‐resolving ocean circulation model (JCOPE‐T) well reproduced the observed nature of internal tides, including seasonal variationsThe temperature anomaly contours of the modeled internal tides tended to be subparallel to the acoustically detected reflecting layers [ABSTRACT FROM AUTHOR]

Abstract: An array of 10 absolute pressure gauges (APGs) deployed in deep water 50 km east of Aogashima, an island in southern Japan, observed several isolated signals in the infragravity wave (IGW) frequency band (0.002–0.03 Hz) during boreal summer, whereas relatively high IGW energy persisted during boreal winter. The isolated IGW shows dispersion with a delay time of 4–5 days as a function of frequency. Here we estimate the excitation locations of IGWs for the two seasons with estimated incoming direction of IGW, calculation of transoceanic IGW trajectories and propagation times, and spatiotemporal variations of significant wave heights from WAVEWATCH III. In boreal summer, the isolated IGWs are primarily caused by IGW energies excited at the shoreline of South America, based on the following three observations: IGWs observed at the array originated from the east: the easterly ray path from the array reaches South America: and an event‐like IGWs were observed at the array when a storm approaches eastward to the shoreline of South America, in which the observed delay time of 4–5 days was also supported by the frequency‐dependent calculation of IGW propagation times. In boreal winter, the incessant IGWs consist of transoceanic IGW energies leaked from the shoreline, primarily from North America, and secondly from South America and the western Aleutian Islands. [ABSTRACT FROM AUTHOR]

Shear wave splitting measurements provide significant information about subduction zone mantle flow, which is closely tied to plate motions, lithospheric deformation, arc volcanism, and backarc spreading processes. We analyse the shear wave splitting of local S waves recorded by a large 2003–2004 deployment consisting of 58 ocean-bottom seismographs (OBSs) and 20 land stations and by nine OBSs from a smaller 2001–2002 deployment. We employ several methods and data processing schemes, including spatial averaging methods, to obtain stable and consistent shear wave splitting patterns throughout the arc–backarc system. Observed fast orientation solutions are dependent on event location and depth, suggesting that anisotropic fabric in the mantle wedge is highly heterogeneous. Shear waves sampling beneath the northern island arc (latitudes 17.5°–19°N) and between the arc and backarc spreading centre show arc-parallel fast orientations for events shallower than 250 km depth; whereas, fast orientations at the same stations are somewhat different for deeper events. Waves sampling beneath the central island arc stations (latitudes 15.5°–17.5°) show fast orientations subparallel to both the arc and absolute plate motion (APM) for events <250 km depth and APM-parallel for deeper events. Ray paths sampling west of the spreading centre show fast orientations ranging from arc-perpendicular to APM-parallel. Arc-parallel fast orientations characterize the southern part of the arc with variable orientations surrounding Guam. These results suggest that the typical interpretation of mantle wedge flow strongly coupled to the downgoing slab is valid only at depths greater than ∼250 km and at large distances from the trench. We conclude that the arc-parallel fast orientations are likely the result of physical arc-parallel mantle flow and are not due to recently proposed alternative lattice preferred orientation mechanisms and fabrics. This flow pattern may result from along-strike pressure gradients in the mantle wedge, possibly due to changes in slab dip and/or convergence angles. [ABSTRACT FROM AUTHOR]

Abstract: We analyzed seismic waveforms recorded by the broadband ocean bottom seismographs deployed in the South Pacific superswell to determine the depths of the mantle discontinuities using a receiver function method. We estimated the thickness of the mantle transition zone (MTZ) to be 245km on average beneath the superswell region, which is close to the global average. The MTZ is found to be thinned locally beneath the Society hot spot by 30km. Temperature anomalies computed from the thinned transition zone and the Clapeyron slope of the olivine phase transformations are 150–200K beneath the Society hot spot. Previous studies, using land-based data, suggested the presence of a hot MTZ beneath the Pitcairn hot spot. The locally hot transition zone beneath the hot spots is attributed to narrow mantle plumes probably rising from the lower mantle. The normal average thickness obtained from the present study indicates that there is no broad upwelling across the transition zone beneath the entire superswell region at present. [Copyright &y& Elsevier]

We obtained phase velocities of fundamental Rayleigh waves in the northwestern Pacific ocean and the northern Philippine sea from seismograms retrieved from a long-term broad-band ocean bottom seismometer (LT-OBS) array deployed in 1999–2000 and from those recorded in Japan, Guam and Ponape islands. This array observation was one of the first attempts to record continuous seismograms on the seafloor using broad-band seismographs on a long-term basis. The geographical distribution of the LT-OBS stations and the surrounding land stations enabled us to determine pure-path phase velocities in a frequency range from 0.01 to 0.05 Hz across the Mariana trough, the Parece Vela basin, the Shikoku basin and the Minami Daito basin, which were found to be systematically lower than those of the Pacific seafloor at comparable ages. This result, along with other geophysical and geological observations in the Philippine sea, may be explained by an uppermost mantle that is relatively Fe rich. [ABSTRACT FROM AUTHOR]

Abstract: The crustal and lithospheric mantle structure at the south segment of the west Iberian margin was investigated along a 370 km long seismic transect. The transect goes from unthinned continental crust onshore to oceanic crust, crossing the ocean–continent transition (OCT) zone. The wide-angle data set includes recordings from 6 OBSs and 2 inland seismic stations. Kinematic and dynamic modeling provided a 2D velocity model that proved to be consistent with the modeled free-air anomaly data. The interpretation of coincident multi-channel near-vertical and wide-angle reflection data sets allowed the identification of four main crustal domains: (i) continental (east of 9.4°W); (ii) continental thinning (9.4°W–9.7°W); (iii) transitional (9.7°W–∼10.5°W); and (iv) oceanic (west of ∼10.5°W). In the continental domain the complete crustal section of slightly thinned continental crust is present. The upper (UCC, 5.1–6.0 km/s) and the lower continental crust (LCC, 6.9–7.2 km/s) are seismically reflective and have intermediate to low P-wave velocity gradients. The middle continental crust (MCC, 6.35–6.45 km/s) is generally unreflective with low velocity gradient. The main thinning of the continental crust occurs in the thinning domain by attenuation of the UCC and the LCC. Major thinning of the MCC starts to the west of the LCC pinchout point, where it rests directly upon the mantle. In the thinning domain the Moho slope is at least 13° and the continental crust thickness decreases seaward from 22 to 11 km over a ∼35 km distance, stretched by a factor of 1.5 to 3. In the oceanic domain a two-layer high-gradient igneous crust (5.3–6.0 km/s; 6.5–7.4 km/s) was modeled. The intra-crustal interface correlates with prominent mid-basement, 10–15 km long reflections in the multi-channel seismic profile. Strong secondary reflected PmP phases require a first order discontinuity at the Moho. The sedimentary cover can be as thick as 5 km and the igneous crustal thickness varies from 4 to 11 km in the west, where the profile reaches the Madeira-Tore Rise. In the transitional domain the crust has a complex structure that varies both horizontally and vertically. Beneath the continental slope it includes exhumed continental crust (6.15–6.45 km/s). Strong diffractions were modeled to originate at the lower interface of this layer. The western segment of this transitional domain is highly reflective at all levels, probably due to dykes and sills, according to the high apparent susceptibility and density modeled at this location. Sub-Moho mantle velocity is found to be 8.0 km/s, but velocities smaller than 8.0 km/s confined to short segments are not excluded by the data. Strong P-wave wide-angle reflections are modeled to originate at depth of 20 km within the lithospheric mantle, under the eastern segment of the oceanic domain, or even deeper at the transitional domain, suggesting a layered structure for the lithospheric mantle. Both interface depths and velocities of the continental section are in good agreement to the conjugate Newfoundland margin. A ∼40 km wide OCT having a geophysical signature distinct from the OCT to the north favors a two pulse continental breakup. [Copyright &y& Elsevier]

Abstract: Three-dimensional P-wave velocity structure of the mantle beneath the South Pacific Superswell is determined through passive broadband seismic experiments on the ocean floor and islands between 2003 and 2005. We collected approximately 1500 relative times of long-period teleseismic P-waves by using a waveform cross-correlation. We analyzed this data set with relative time tomography to depths of 2000km. The resultant structure shows lateral heterogeneity of approximately ±2%, in which a distinct low velocity region is found beneath the center of the Superswell at a depth of 1600km. At 1200km depth, an elongated low velocity region is found beneath the Society to Pitcairn hotspots. At 800km depth, two linear low velocity regions are located beneath Tuamotu and Austral islands. Isolated low velocity regions are identified beneath the Society, Marquesas, and Macdonald hotspots at 400km depth. Our new tomographic images reveal that the large low velocity region rooted in the deep lower mantle is split into two sheets at 1200km depth and these terminate at approximately 800km depth. This feature appears to be consistent with the characteristics of a thermo-chemical pile or dome. [Copyright &y& Elsevier]

Five lineaments on the volcanic Vøring Margin, NE Atlantic, have been identified in crustal scale models derived from Ocean Bottom Seismograph (OBS) data. It is suggested that the Vøring Basin can be divided in four compartments bounded by the Jan Mayen Fracture Zone/Lineament, a new lineament defined from this study, the Gleipne Lineament, the Surt Lineament and the Bivrost Lineament. The NW–SE trending Jan Mayen-, Gleipne- and Bivrost lineaments probably represent old zones of weakness controlling the onset of the early Eocene seafloor spreading, whereas the Surt- and New lineaments, rotated ca. 30° symmetrically from the azimuth of the Gleipne Lineament, may represent adjustment features related to the early Cretaceous/early Tertiary rifting. The longest landward extent of a lower crustal high-velocity body, assumed to represent intrusions related to the last phase of rifting, is found between the New Lineament and the Gleipne Lineament, where the body extends across the Helland Hansen Arch. Northeastwards in the Vøring Basin, the landward limit of the body steps gradually seawards, closely related to the interpreted lineaments. Northeast of the Gleipne Lineament, the body terminates close to the Fles Fault Complex, north of the Surt Lineament, it extends across the Nyk High, and northeast of the Bivrost Lineament the intrusions terminate around the Vøring Escarpment. Evidence for an interplay between active and passive rifting components is found on regional and local scales on the margin. The active component is evident through the decrease in magmatism with increased distance from the Icelandic plume, and the passive component is documented through the fact that all found crustal lineaments to a certain degree acted as barriers to magma emplacement. The increased thickness of the continental crust on the seaward side of the Vøring Escarpment, the upwarping of Moho and thinning of the lower crustal high-velocity layer in the western part of the Vøring Basin, as well as a strong shallowing of the Moho observed in parts of the area between the Jan Mayen Fracture Zone/Lineament and the New Lineament, can be explained by lithospheric delamination models. [Copyright &y& Elsevier]

A total of 13 regional Ocean Bottom Seismograph (OBS) profiles with an accumulated length of 2207 km acquired on the Vøring Margin, NE Atlantic have been travel time modelled with regards to S-waves. The Vp/Vs ratios are found to decrease with depth through the Tertiary layers, which is attributed to increased compaction and consolidation of the rocks. The Vp/Vs ratio in the intra-Campanian to mid-Campanian layer (1.75–1.8) in the central Vøring Basin is significantly lower than for the layers above and beneath, suggesting higher sand/shale ratio. This layer was confirmed by drilling to represent a layer of sandstone. This mid-Cretaceous ‘anomaly’ is also present in the northern Vøring Basin, as well as on the southern Lofoten Margin further north. The Vp/Vs ratio in the extrusive rocks on the Vøring Plateau is estimated to be 1.85, conformable with mafic (basaltic) rocks. Landward of the continent/ocean transition (COT), the Vp/Vs ratio in the layer beneath the volcanics is estimated to be 1.67–1.75. These low values suggest that this layer represents sedimentary rocks, and that the sand/shale ratio might be relatively high here. The Vp/Vs ratio in the crystalline basement is estimated to be 1.67–1.75 in the basin and on the landward part of the Vøring Plateau, indicating the presence of granitic/granodioritic continental crust. In the lower crust, the Vp/Vs ratio in the basin decreases uniformly from southwest to northeast, from 1.85–1.9 to 1.68–1.73, suggesting a gradual change from mafic (gabbroic) to felsic (granodioritic) lower crust. Significant (3–5%) azimuthal S-wave anisotropy is observed for several sedimentary layers, as well as in the lower crust. All these observations can be explained by invoking the presence of liquid-filled microcracks aligned vertically along the direction of the present day maximum compressive stress (NW–SE). [Copyright &y& Elsevier]

Background: Treatment for regional lymph node recurrence after initial treatment for esophageal squamous cell carcinoma (ESCC) differs among institutions. Though some retrospective cohort studies have shown that lymphadenectomy for cervical lymph node recurrence is safe and leads to long-term survival, the efficacy remains unclear. In this study, we investigated the long-term outcomes of patients who underwent lymphadenectomy for regional recurrence after treatment for ESCC., Patients and Methods: We retrieved 20 cases in which lymphadenectomy was performed for lymph node recurrence after initial treatment for ESCC in our hospital from January 2003 to December 2016. Initial treatments included esophagectomy, endoscopic resection (ER) and chemoradiotherapy/chemotherapy (CRT/CT). Overall survival (OS) and recurrence-free survival (RFS) after lymphadenectomy were calculated by the Kaplan-Meier method. We also used a univariate analysis with a Cox proportional hazards model to determine factors influencing the long-term outcomes., Results: The five-year OS and RFS of patients who underwent secondary lymphadenectomy for recurrence after initial treatment were 50.0% and 26.7%, respectively. The five-year overall survival rates of patients who received esophagectomy, ER and CRT/CT as initial treatments, were 40.0%, 75.0% and 50.0%, respectively. The five-year OS rates of patients with Stage I and Stage II-IVB at initial treatments were 83.3% and 33.3%, respectively., Conclusions: Lymphadenectomy for regional recurrence after initial treatment for ESCC is effective to some degree. Patients with regional recurrence after initial treatment for Stage I ESCC have a good prognosis; thus, lymphadenectomy should be considered for these cases., (© 2022. The Author(s).)

We investigated the seismological structure beneath the equatorial Melanesian region, where is tectonically unique because an immense oceanic plateau, a volcanic chain and subduction zones meet. We conducted a multi-frequency P-wave tomography using data collected from an approximately 2-year-long seismic experiment around the Ontong Java Plateau (OJP). High-velocity anomalies were revealed beneath the center of the OJP at a depth of ~ 150 km, the middle-eastern edge of the OJP at depths of 200-300 km, and in the mantle transition zone beneath and around the OJP; low-velocity anomalies were observed along the Caroline volcanic island chain above 450 km depth. These anomalies are considered to be associated with the thick lithosphere of the OJP, remnant dipping Pacific slab, stagnant Pacific slab, and a sheet-like upwelling. The broad stagnant slab was formed due to rapid trench retreat from 48 to 25 Ma until when the OJP with thick lithosphere collided with a subduction boundary of the Pacific and Australian plates. This collision triggered slab breakoff beneath the arc where the dipping slab remained. The stagnant Pacific slab in the mantle transition zone restricted the plume upwelling from the lower mantle causing sheet-like deformed upwelling in the upper mantle., (© 2021. The Author(s).)

Tsunami earthquakes are a group of enigmatic earthquakes generating disproportionally large tsunamis relative to seismic magnitude. These events occur most typically near deep-sea trenches. Tsunami earthquakes occurring approximately every 10 years near Torishima on the Izu-Bonin arc are another example. Seismic and tsunami waves from the 2015 event [ M w (moment magnitude) = 5.7] were recorded by an offshore seafloor array of 10 pressure gauges, ~100 km away from the epicenter. We made an array analysis of dispersive tsunamis to locate the tsunami source within the submarine Smith Caldera. The tsunami simulation from a large caldera-floor uplift of ~1.5 m with a small peripheral depression yielded waveforms remarkably similar to the observations. The estimated central uplift, 1.5 m, is ~20 times larger than that inferred from the seismologically determined non-double-couple source. Thus, the tsunami observation is not compatible with the published seismic source model taken at face value. However, given the indeterminacy of M zx , M zy , and M {tensile} of a shallow moment tensor source, it may be possible to find a source mechanism with efficient tsunami but inefficient seismic radiation that can satisfactorily explain both the tsunami and seismic observations, but this question remains unresolved.

We recorded P and S waves traveling through the oceanic lithosphere-asthenosphere system (LAS) using broadband ocean-bottom seismometers in the northwest Pacific, and we quantitatively separated the intrinsic (anelastic) and extrinsic (scattering) attenuation effects on seismic wave propagation to directly infer the thermomechanical properties of the oceanic LAS. The strong intrinsic attenuation in the asthenosphere obtained at higher frequency (~3 hertz) is comparable to that constrained at lower frequency (~100 seconds) by surface waves and suggests frequency-independent anelasticity, whereas the intrinsic attenuation in the lithosphere is frequency dependent. This difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and provides new insight into what distinguishes the asthenosphere from the lithosphere., (Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

The free radical scavenger edaravone is able to stimulate prostacyclin release and inhibit the lipoxygenase pathway in the arachidonic acid cascade. The effect of edaravone administration on myocardial damage in rabbit hearts subjected to ischaemia-reperfusion was examined at different times relative to reperfusion. All rabbits underwent sustained coronary artery occlusion for 30 min followed by 3 h of reperfusion. Rabbits were divided into the following groups: control; early (3 mg/kg edaravone IV 10 min before reperfusion); immediate (3 mg/kg edaravone IV immediately after the start of reperfusion); and late (3, 6 or 10 mg/kg edaravone IV 5 min after the start of reperfusion). Single bolus administration of edaravone 10 min before reperfusion or immediately upon initiation of reperfusion appears to be associated with reductions in infarction size and the percentage of apoptotic cells, but treatment with edaravone 5 min after initiation of reperfusion does not appear to have this protective effect.

Morphological changes of blood vessel walls including various kinds of capillaries have been induced by administration of soluble immune complexes. After repeated administrations, those experimental animals who survived the phase of initial anaphylactic shock developed osteomyelitis. In this paper, the formative processes of osteomyelitis will be discussed in relation to Aschoff's definition of inflammation. We will emphasize the importance of the capillarization of the sinusoidal endothelia for the formation of osteomyelitis.

The rheological characteristics of a model matrix, consisting of Bacto-agar, were correlated with the ability of the matrix to permit cellular penetration, using a rheolometer and the agar bullet method. The most important rheologic characteristic that affected cellular mobility was found to be the viscosity rate. A viscosity rate under 1,000 X 10(4) dyne sec/cm2 was needed to permit cellular mobility.