The relationship between Doppler indices from inferior vena cava and hepatic veins in normal human fetuses.

This study was conducted to determine the gestational age-related reference range of the preload index [peak velocity during atrial contraction (A)/peak velocity during ventricular systole (S)] for the inferior vena cava (IVC), the right hepatic vein, the middle hepatic vein and the left hepatic vein. The slope and the intercept of the regression line for each preload index were compared among the 4 veins using analysis of covariance. Doppler measurements were obtained for the 4 veins of 316 normal fetuses at 22-40 weeks of gestation. A and S values were measured from the recorded flow velocity waveform of each vein and the A/S ratio was calculated as the preload index. The regression lines for the preload index of the 4 veins decreased gradually throughout gestation. Analysis of covariance revealed no significant differences in the slopes of the regression lines for the 4 veins. However, the intercepts of the regression lines for all hepatic veins were significantly higher than that of the regression line for the IVC (P&#60;0.0001), with the difference ranging from 0.024 to 0.033. There were no significant differences among the intercepts of the regression lines for different hepatic veins. We concluded that the relationship between the preload index and the duration of gestation was statistically similar for all hepatic veins, and strongly resembled that for the IVC.</p

Ultrafine-scale magnetostratigraphy of marine ferromanganese crust

http://geology.geoscienceworld.org/content/39/3/227.full.pdf+htmlHydrogenetic ferromanganese crusts are iron-manganese oxide chemical precipitates on the seafloor that grow over periods of tens of millions of years. Their secular records of chemical, mineralogical, and textural variations are archives of deep-sea environmental changes. However, environmental reconstruction requires reliable high-resolution age dating. Earlier chronological methods using radiochemical and stable isotopes provided age models for ferromanganese crusts, but have limitations on the millimeter scale. For example, the reliability of 10Be/9Be chronometry, commonly considered the most reliable technique, depends on the assumption that the production and preservation of 10Be are constant, and requires accurate knowledge of the 10Be half-life. To overcome these limitations, we applied an alternative chronometric technique, magnetostratigraphy, to a 50-mm-thick hydrogenetic ferromanganese crust (D96-m4) from the northwest Pacific. Submillimeter-scale magnetic stripes originating from approximately oppositely magnetized regions oriented parallel to bedding were clearly recognized on thin sections of the crust using a high-resolution magnetometry technique called scanning SQUID (superconducting quantum interference device) microscopy. By correlating the boundaries of the magnetic stripes with known geomagnetic reversals, we determined an average growth rate of 5.1 ± 0.2 mm/m.y., which is within 16% of that deduced from the 10Be/9Be method (6.0 ± 0.2 mm/m.y.). This is the finest-scale magnetostratigraphic study of a geologic sample to date. Ultrafine-scale magnetostratigraphy using SQUID microscopy is a powerful new chronological tool for estimating ages and growth rates for hydrogenetic ferromanganese crusts. It provides chronological constraints with the accuracy promised by the astronomically calibrated magnetostratigraphic time scale (1–40 k.y.).Japan Society for the Promotion of Science (Grant-in-Aid for Scientific Research (21654071))National Science Foundation (U.S.) (Collaboration in Mathematical Geosciences Program

Scanning SQUID microscope system for geological samples: system integration and initial evaluation

We have developed a high-resolution scanning superconducting quantum interference device (SQUID) microscope for imaging the magnetic field of geological samples at room temperature. In this paper, we provide details about the scanning SQUID microscope system, including the magnetically shielded box (MSB), the XYZ stage, data acquisition by the system, and initial evaluation of the system. The background noise in a two-layered PC permalloy MSB is approximately 40–50 pT. The long-term drift of the system is approximately ≥1 nT, which can be reduced by drift correction for each measurement line. The stroke of the XYZ stage is 100 mm × 100 mm with an accuracy of ~10 µm, which was confirmed by laser interferometry. A SQUID chip has a pick-up area of 200 µm × 200 µm with an inner hole of 30 µm × 30 µm. The sensitivity is 722.6 nT/V. The flux-locked loop has four gains, i.e., ×1, ×10, ×100, and ×500. An analog-to-digital converter allows analog voltage input in the range of about ±7.5 V in 0.6-mV steps. The maximum dynamic range is approximately ±5400 nT, and the minimum digitizable magnetic field is ~0.9 pT. The sensor-to-sample distance is measured with a precision line current, which gives the minimum of ~200 µm. Considering the size of pick-up coil, sensor-to-sample distance, and the accuracy of XYZ stage, spacial resolution of the system is ~200 µm. We developed the software used to measure the sensor-to-sample distance with line scan data, and the software to acquire data and control the XYZ stage for scanning. We also demonstrate the registration of the magnetic image relative to the optical image by using a pair of point sources placed on the corners of a sample holder outside of a thin section placed in the middle of the sample holder. Considering the minimum noise estimate of the current system, the theoretical detection limit of a single magnetic dipole is ~1 × 10-14 Am2. The new instrument is a powerful tool that could be used in various applications in paleomagnetism such as ultrafine-scale magnetostratigraphy and single-crystal paleomagnetism

Possibility of Non-destructive magnetic detection of thin ash layers in ice cores

第3回極域科学シンポジウム/第35回極域気水圏シンポジウム 11月29日（木） 国立国語研究所 ２階ロビ