Kinematics of Cretaceous to tertiary Pacific Plate : discussion from Ar-Ar age and geochemistry of within-plate basalts

太平洋プレート北西部には，大西洋やインド洋，太平洋東部，南部などの他の海域に比べて，異常とも言える数の海山列や海台が存在しており，これらの海山列では，東南東―西北西，南東―北西，および北東―南西方向の各海山列が複雑に考査しているように見える。ホットスポット説に基づくと，海山列の方向，形成年代は，過去の海洋プレートの移動方向，移動速度を示すことが知られている。中でもホットスポットにより形成された海山列の代表であり，太平洋プレートの運動を知る上で最も重要なハフイー天皇海山列は，後期白亜紀後半以降の海山列であるが，この時代以前の太平洋プレート運動は，解明されていなかった。このため，本研究地域である北西太平洋の海山群の研究が必要であった。　本論では，海山から得られた岩石試料のAr-Ar年代を測定し，全岩化学組成，含有鉱物の化学組成の分析を行い，白亜紀後期以前の太平洋プレートの運動を解明した。その結果，以下のことが判明した。　日本海溝海側斜面：日本海溝海側斜面のアルカリ玄武岩の年代結果は，白亜紀という予想に反して5.95±0.31Maの年代結果が得られた。この岩石中にかんらん石の捕獲結晶が存在すること，および単斜輝石化学組成は，ハワイやサモア火山において，地殻内の割れ目に起因して小規模に噴出する回春期火山活動期の噴出物の特徴と似ている。その結果，この岩石の起源は「海洋地殻の割れ目」から小規模に噴出するマグマであろうというモデルを提唱した。この研究によって，現在まで知られていなかった種類の玄武岩を発見した。年代結果から太平洋プレートの移動速度に基づいて位置を戻すと，現在のアウタースウェル（北海道海膨）突入直前の位置（南東方およそ600km）となる。「海洋地殻の割れ目」は，そのアウタースウェルヘ突入する際の海洋地殻の屈曲が原因となった可能性が高いと推論した。　マゼラン海山列：マゼラン海山列上の福永海山では，プレート内火山の火山層所の中で盾状火山形成期の最後期に噴出する岩石である流紋岩から127.0±5.2Maの前期白亜紀の年代結果が得られた。この結果は，盾状火山形成期主期の活動期と考えられる，アルカリ玄武岩を含む凝灰質泥岩の化石年代（140Ma以前）に比べて10百万年程度若いことが判明した。これは，現在のハワイホットスポットの盾状火山形成期間が数百万年間であるのに対して異常に長い。この事実は，当時の太平洋プレートの移動速度が低速であるために，海山がホットスポットの熱源をなかなか通過できず，噴火活動期間が長期に及んでいたことを示唆する。また，この活動期間の見積もりを既に年代結果が得られているヘムラー海山にも応用し，マゼラン海山列中のマリアナ海溝側の北東―南西方向海山列を，前期白亜紀のホットスポットトラックと同定した。　このマゼラン海山列の結果をもとに，前期白亜紀太平洋プレートのオイラー極を見積もった。オイラー極は，あるプレートの移動方向，移動速度を地球回転体に反映し，回転極，回転角速度として表示するものであり，球面上の正弦定理，余弦定理を用いて見積もることが出来る。この結果，120－140Maの太平洋プレートのオイラー極は，北緯40.3度，東経103.7度付近，角速度は0.33度／百万年であることを導いた。従来報告されていた前期白亜紀の太平洋プレートオイラー極は，一つの海山列（中央太平洋海山群またはシャツキー海台）だけから見積もられているのみであった。また，その形成年代は堆積岩の化石年代または古地磁気年代推定しているにとどまっていた。しかし，本研究では初めて2つの海山列（マゼラン海山列，シャツキー海台）から前期白亜紀太平洋プレートのオイラー極を見積もる事が出来た。さらに，Ar-Ar年代によって形成年代を与えたことも，本研究が初めてであり，オイラー極の信頼度がいっそう高いものとなった。 Most seamounts, inlands and atolls on the present Pacific Plate were formed by submarine intra-plate volcanism mainly during the Cretaceous. Such seamounts in the West Pacific Seamount Province (WPSP) indicated that some Cretaceous seamount chains are significant for hotspot trails. ...Thesis (Ph. D. in Science)--University of Tsukuba, (A), no. 2587, 2001.3.23Includes bibliographical referencesTitlepage,Abstract,Contents -- Chapter 1. Introduction -- Chapter 2. Study Areas -- Chapter 3. Methods -- Chapter 4. Joban Seamount Chain & Uyeda Ridge -- Chapter 5. Young Alkali-basalt from Japan Trench -- Chapter 6. Early Cretaceous Seamouont in Magellan Seamount Chain -- Chapter 7. Absolute Motion of Early Cretaceous Pacific Plate -- Chapter 8. Summary -- Acknowledgements -- References -- Appendix A－

Accuracy of Acetabular Cup Implantation, as a Function of Body Mass Index and Soft-tissue Thickness, with a Mechanical Intraoperative Support Device: A Retrospective Observational Study

HipCOMPASS, a mechanical intraoperative support device used in total hip arthroplasty (THA), improves the cup-alignment accuracy. However, the alignment accuracy achieved by HipCOMPASS has not been specifically examined in obese patients. In this study, we retrospectively evaluated the relation between alignment accuracy and several obesity-related parameters in 448 consecutive patients who underwent primary THA using HipCOMPASS. We used computed tomography (CT) to measure the preoperative soft-tissue thickness of the anterior-superior iliac spine (ASIS) and pubic symphysis and the differences between preoperative and postoperative cup angle based on the cup-alignment error. We found significant correlations between the absolute value of radiographic anteversion difference and body mass index (r = 0.205), ASIS thickness (r = 0.419), and pubic symphysis thickness (r = 0.434). The absolute value of radiographic inclination difference was significantly correlated with ASIS (r = 0.257) and pubic symphysis thickness (r = 0.202). The receiver operating characteristic curve showed a pubic symphysis thickness of 37.2 mm for a ≥ 5° implantation error in both radiographic inclination and anteversion simultaneously. The cup-alignment error for HipCOMPASS was large in patients whose pubic symphysis thickness was ≥ 37.2 mm on preoperative CT. Our results indicate that methods other than HipCOMPASS, including computed tomography-based navigation systems, might be preferable in obese patients

Minimally Invasive Spinal Stabilization with Denosumab before Total Spondylectomy for a Collapsing Lower Lumbar Spinal Giant Cell Tumor

A 21-year-old man consulted our hospital for treatment of a spinal giant cell tumor (GCT) of Enneking stage III. Lower lumbar-spine tumors and severe spinal canal stenosis are associated with high risk for surgical mor-bidity. Stability was temporarily secured with a percutaneous pedicle screw fixation in combination with deno-sumab, which shrank the tumor. Total en bloc spondylectomy was then performed 6 months after initiation of denosumab, and the patient was followed for 3 years. There was no local recurrence, and bony fusion was obtained. Minimally invasive surgery and denosumab allowed safer and easier treatment of a collapsing lower lumbar extra-compartmental GCT

Secondary outflow driven by the protostar Ser-emb 15 in Serpens

We present the detection of a secondary outflow associated with a Class I source, Ser-emb 15, in the Serpens Molecular Cloud. We reveal two pairs of molecular outflows consisting of three lobes, namely primary and secondary outflows, using ALMA 12CO and SiO line observations at a resolution of 318 au. The secondary outflow is elongated approximately perpendicular to the axis of the primary outflow in the plane of the sky. We also identify two compact structures, Sources A and B, within an extended structure associated with Ser-emb 15 in the 1.3 mm continuum emission at a resolution of 40 au. The projected sizes of Sources A and B are 137 au and 60 au, respectively. Assuming a dust temperature of 20 K, we estimate the dust mass to be 0.0024 Msun for Source A and 0.00033 Msun for Source B. C18O line data imply the existence of rotational motion around the extended structure, however, cannot resolve rotational motion in Source A and/or B, due to insufficient angular and frequency resolutions. Therefore, we cannot conclude whether Ser-emb 15 is a single or binary system. Thus, either Source A or B could drive the secondary outflow. We discuss two scenarios to explain the driving mechanism of the primary and secondary outflows: the Ser-emb 15 system is (1) a binary system composed of Source A and B or (2) a single star system composed of only Source A. In either case, the system could be a suitable target for investigating the disk and/or binary formation processes in complicated environments. Detecting these outflows should contribute to understanding complex star-forming environments, which may be common in the star-formation processes.Comment: 21 pages, 10 figures, Accepted for publication in the Astrophysical Journa

Crescent-Shaped Molecular Outflow from the Intermediate-mass Protostar DK Cha Revealed by ALMA

We report on an Atacama Large Millimeter/submillimeter Array (ALMA) study of the Class I or II intermediate-mass protostar DK Cha in the Chamaeleon II region. The 12CO (J=2-1) images have an angular resolution of ~1'' (~250 au) and show high-velocity blueshifted (>70 km s-1) and redshifted (>50 km s-1) emissions which have 3000 au scale crescent-shaped structures around the protostellar disk traced in the 1.3mm continuum. Because the high-velocity components of the CO emission are associated with the protostar, we concluded that the emission traces the pole-on outflow. The blueshifted outflow lobe has a clear layered velocity gradient with a higher velocity component located on the inner side of the crescent shape, which can be explained by a model of an outflow with a higher velocity in the inner radii. Based on the directly driven outflow scenario, we estimated the driving radii from the observed outflow velocities and found that the driving region extends over two orders of magnitude. The 13CO emission traces a complex envelope structure with arc-like substructures with lengths of ~1000au. We identified the arc-like structures as streamers because they appear to be connected to a rotating infalling envelope. DK Cha is useful for understanding characteristics that are visible by looking at nearly face-on configurations of young protostellar systems, providing an alternative perspective for studying the star-formation process.Comment: Accepted for publication in ApJ. 12 pages, 5 figure

Validation of CyTOF Against Flow Cytometry for Immunological Studies and Monitoring of Human Cancer Clinical Trials

Flow cytometry is a widely applied approach for exploratory immune profiling and biomarker discovery in cancer and other diseases. However, flow cytometry is limited by the number of parameters that can be simultaneously analyzed, severely restricting its utility. Recently, the advent of mass cytometry (CyTOF) has enabled high dimensional and unbiased examination of the immune system, allowing simultaneous interrogation of a large number of parameters. This is important for deep interrogation of immune responses and particularly when sample sizes are limited (such as in tumors). Our goal was to compare the accuracy and reproducibility of CyTOF against flow cytometry as a reliable analytic tool for human PBMC and tumor tissues for cancer clinical trials. We developed a 40+ parameter CyTOF panel and demonstrate that compared to flow cytometry, CyTOF yields analogous quantification of cell lineages in conjunction with markers of cell differentiation, function, activation, and exhaustion for use with fresh and viably frozen PBMC or tumor tissues. Further, we provide a protocol that enables reliable quantification by CyTOF down to low numbers of input human cells, an approach that is particularly important when cell numbers are limiting. Thus, we validate CyTOF as an accurate approach to perform high dimensional analysis in human tumor tissue and to utilize low cell numbers for subsequent immunologic studies and cancer clinical trials