Early trace of life from 3.95 Ga sedimentary rocks in Labrador, Canada.

The vestiges of life in Eoarchean rocks have the potential to elucidate the origin of life. However, gathering evidence from many terrains is not always possible, and biogenic graphite has thus far been found only in the 3.7-3.8 Ga (gigayears ago) Isua supracrustal belt. Here we present the total organic carbon contents and carbon isotope values of graphite (δ13Corg) and carbonate (δ13Ccarb) in the oldest metasedimentary rocks from northern Labrador. Some pelitic rocks have low δ13Corg values of -28.2, comparable to the lowest value in younger rocks. The consistency between crystallization temperatures of the graphite and metamorphic temperature of the host rocks establishes that the graphite does not originate from later contamination. A clear correlation between the δ13Corg values and metamorphic grade indicates that variations in the δ13Corg values are due to metamorphism, and that the pre-metamorphic value was lower than the minimum value. We concluded that the large fractionation between the δ13Ccarb and δ13Corg values, up to 25‰, indicates the oldest evidence of organisms greater than 3.95 Ga. The discovery of the biogenic graphite enables geochemical study of the biogenic materials themselves, and will provide insight into early life not only on Earth but also on other planets.

Development of a removable head fixation device for longitudinal behavioral and imaging studies in rats.

BACKGROUND: In some behavioral neuroscience studies, an attachment is surgically fixed onto the head of an awake animal to allow the animal to perform learning tasks repeatedly in the same position in a task-training system. A recently developed task-training system enables operant conditioning of head-fixed rats within only a few days, and this system has been rigorously applied to record learning-associated neural activity using electrophysiological techniques. However, the head attachment of this device is made of metal and thus is not suitable for simultaneous brain imaging studies with X-ray computed tomography (CT), magnetic resonance imaging (MRI) or positron emission tomography (PET). NEW METHOD: We developed a novel head fixation device with a removable attachment to position the rat head precisely in both imaging and training devices across different sessions. The device consisted of a removable attachment, a clamp and a stage, all of which were made of PET/MRI compatible acrylic resin. We tested the usefulness of the device with (18)F-fluorodeoxyglucose (FDG) PET and CT. RESULTS: The new device did not substantially affect (18)F-FDG PET images. Repositioning of the rat's head across sessions and experimenters was at a level of submillimeter accuracy. COMPARISON WITH EXISTING METHOD: The errors of radioactivity concentration of (18)F-FDG in the PET image were lower with the present attachment than with the conventional metal attachment. Repositioning accuracy was considerably improved compared with a visual inspection method. CONCLUSIONS: The developed fixation device is useful for longitudinal behavioral and brain imaging studies in rats.

Fe-Ni composition dependence of magnetic anisotropy in artificially fabricated L1 0-ordered FeNi films.

We prepared L10-ordered FeNi alloy films by alternate deposition of Fe and Ni monatomic layers, and investigated their magnetic anisotropy. We employed a non-ferromagnetic Au-Cu-Ni buffer layer with a flat surface and good lattice matching to L10-FeNi. An L10-FeNi film grown on Au6Cu51Ni43 showed a large uniaxial magnetic anisotropy energy (Ku = 7.0 × 10(6) erg cm(-)3). Ku monotonically increased with the long-range order parameter (S) of the L10 phase. We investigated the Fe-Ni composition dependence by alternating the deposition of Fe 1 − x and Ni 1 + x monatomic layers (− 0.4 < x < 0.4). Saturation magnetization (Ms) and Ku showed maxima (Ms = 1470 emu cm(-3), Ku = 9.3 × 10(6) erg cm(-3)) for Fe60Ni40 (x = -0.2) while S showed a maximum at the stoichiometric composition (x = 0). The change in the ratio of lattice parameters (c/a) was small for all compositions. We found that enrichment of Fe is very effective to enhance Ku. The large Ms and Ku of Fe60Ni40 indicate that Fe-rich L10-FeNi is promising as a rare-earth-free permanent magnet.

A novel type of implantable and programmable infusion pump for small laboratory animals.

INTRODUCTION: The iPRECIO (Primetech Corporation, Tokyo, Japan) is a new form of pump for infusing small laboratory animals. The key features of the iPRECIO are that it can be implanted within the animal, it is refillable, and it is programmable. The infusion start-points and end-points are adjustable, infusion rate can be altered, and the infusion solution can be changed after the pump is implanted. In order to confirm the precision of the iPRECIO, in vivo and in vitro experiments were employed. METHODS: In the in vitro experiment, at the excretion rate of 1 microl/h for 336 h, 15 microl/h for 96 h, and 30 microl/h for 120 h, the decrease in each pump weight was used to estimate the actual excretion volume. In the in vivo experiments, the iPRECIO was chronically implanted in rats, angiotensin II was infused, and arterial pressure (AP) was monitored. RESULTS: In the in vitro experiment, the volume of solution excreted from the pump increased with time, and the volume excreted matched the programmed volume. The infusion rate also changed at the scheduled time. In the in vivo experiment, AP increased and decreased on schedule, and a dose-dependent pressor response to angiotensin II occurred. Furthermore, after exchanging saline with angiotensin II, AP increased and decreased on schedule. DISCUSSION: Present data of the in vitro and in vivo experiments indicates that the iPRECIO worked precisely, making it suitable for a variety of experiments involving small laboratory animals.