Signatures of Quantum-Tunneling Diffusion of Hydrogen Atoms on Water Ice at 10 K.

Reported here is the first observation of the tunneling surface diffusion of a hydrogen (H) atom on water ice. Photostimulated desorption and resonance-enhanced multiphoton ionization methods were used to determine the diffusion rates at 10 K on amorphous solid water and polycrystalline ice. H-atom diffusion on polycrystalline ice was 2 orders of magnitude faster than that of deuterium atoms, indicating the occurrence of tunneling diffusion. Whether diffusion is by tunneling or thermal hopping also depends on the diffusion length of the atoms and the morphology of the surface. Our findings contribute to a better understanding of elementary physicochemical processes of hydrogen on cosmic ice dust.

Nanodiamond finding in the hyblean shallow mantle xenoliths.

Most of Earth's diamonds are connected with deep-seated mantle rocks; however, in recent years, µm-sized diamonds have been found in shallower metamorphic rocks, and the process of shallow-seated diamond formation has become a hotly debated topic. Nanodiamonds occur mainly in chondrite meteorites associated with organic matter and water. They can be synthesized in the stability field of graphite from organic compounds under hydrothermal conditions. Similar physicochemical conditions occur in serpentinite-hosted hydrothermal systems. Herein, we report the first finding of nanodiamonds, primarily of 6 and 10 nm, in Hyblean asphaltene-bearing serpentinite xenoliths (Sicily, Italy). The discovery was made by electron microscopy observations coupled with Raman spectroscopy analyses. The finding reveals new aspects of carbon speciation and diamond formation in shallow crustal settings. Nanodiamonds can grow during the hydrothermal alteration of ultramafic rocks, as well as during the lithogenesis of sediments bearing organic matter.

Temperature, composition, and hydrogen isotope effect in the hydrogenation of CO on amorphous ice surface at 10-20 K.

An experiment on the addition reaction of a D atom (deuteration) to CO on a cold ice surface is performed by deuterium atom exposure of three types of samples (pure solid CO, CO-capped H2O ice, and CO-H2O mixed ice) at 10-20 K. The variation of IR absorption spectra for the samples was measured by a Fourier transform infrared spectrometer during exposure to deuterium atoms. Reactions on pure solid CO were observed only at 10 K, while reactions on CO-capped H2O ice and CO-H2O mixed ice were observed to proceed even at 20 K. This indicates that the coexistence of H2O at the surface raises the reactive temperature. In addition, the experiment on H atom exposure was also carried out at 15 K to compare the reaction rate constant between the H and D atoms. The ratio of reaction rate constant kD/kH obtained is about 0.08 at 15 K. The authors provide information on the potential energy for the H+CO reaction at the surface by using the ratio kD/kH and by a model calculation of the potential tunneling with the asymmetric Eckart potential.

Abiotic formation of bioorganic compounds in space--preliminary experiments on ground and future exobiology experiments in space.

Simulation experiments on ground have shown that "amino acid precursors", which give amino acids after acid-hydrolysis, can be formed when an ice mixture simulating ice mantles of interstellar dust particles (lSDs) is irradiated with high energy particles or UV light. It is strongly suggested that such bioorganic compounds were delivered by comets for the first biosphere on the Earth. It is of great interest to confirm this hypothesis in actual space conditions, such as in an exposed facility of JEM. Fundamental designs for such exobiology experiments in earth orbit (EEEO) will be discussed.

A conceptual design for cosmo-biology experiments in Earth's Orbit.

A conceptual design was developed for a cosmo-biology experiment. It is intended to expose simulated interstellar ice materials deposited on dust grains to the space environment. The experimental system consists of a cryogenic system to keep solidified gas sample, and an optical device to select and amplify the ultraviolet part of the solar light for irradiation. By this approach, the long lasting chemical evolution of icy species could be examined in a much shorter time of exposure by amplification of light intensity. The removal of light at longer wavelength, which is ineffective to induce photochemical reactions, reduces the heat load to the cryogenic system that holds solidified reactants including CO as a constituent species of interstellar materials. Other major hardware components were also defined in order to achieve the scientific objectives of this experiment. Those are a cold trap maintained at liquid nitrogen temperature to prevent the contamination of the sample during the exposure, a mechanism to exchange multiple samples, and a system to perform bake-out of the sample exposure chamber. This experiment system is proposed as a candidate payload implemented on the exposed facility of Japanese Experiment Module on International Space Station.

Varioliform mucosal polypoid lesions in intestinal tract in a patient with adult T-cell leukemia.

We describe a case of adult T-cell leukemia (ATL) with intestinal infiltration. In the early clinical stage, the endoscopic findings for the intestine were similar to those of amebic enterocolitis, i.e., varioliform mucosal polypoid lesions, and amebic cyst was detected with stool examination. Although no specific pathological factor could be identified on biopsy, the patient was treated for amebiasis as a diagnostic therapy. The findings of varioliform mucosal polypoid lesions were detected in the duodenum on endoscopic examination, but the lesions eventually disappeared during the treatment for amebiasis. We then suspected lymphoma partially masked by the amebiasis. Immunological staining of a specimen of the colonic mucosa revealed T cell invasion and Southern blotting demonstrated adult T-cell leukemia provirus invasion. Thus, ATL cell infiltration of the intestinal tract was confirmed. It is suggested that systemic disease should also be considered when varioliform mucosal polypoid lesions are found on colonoscopic examination.

[Clinical study of albendazole therapy for strongyloidiasis].

We reported the efficacy of albendazole (ABZ) for the treatment of 27 patients with strongyloidiasis. Twenty-seven patients, 23 males and 4 females, received 200 mg of ABZ one hour before breakfast and supper for 3 days and this treatment was repeated 2 weeks later. The following results were obtained: 1) The eradication rate at 2 weeks after the initial treatment was 70.4% (19 of 27 patients) and 2 weeks after the second course was 66.7% (16 of 24 patients). 2) One patients (3.7%) complained of abdominal pain after the first treatment. Four patients (14.8%) complained of headache (n = 2), nausea (n = 1) and exanthema (n = 1) after the second treatment. But all symptoms were mild and required no treatment and subsided in a few days. 3) Positive rate of HTLV-1 antibody was 45.8% in the patients. As described above, side effects occurred in some cases, although they were mild and transient. From these results, it can be concluded that on increased dose of ABZ could be much more favorable for the treatment of strongyloidiasis.

[Influence of hypercapnia on circulatory response to endotracheal intubation].

Effects of CO2 on circulatory responses to laryngoscopy and endotracheal intubation were investigated in 16 patients under constant depth of enflurane anesthesia (1.2MAC) at different levels of CO2 (normocapnia, PETCO2: 40mmHg or hypercapnia, PETCO2: 60mmHg). Patients were randomly divided into two groups; normocapnia group (n = 8) and hypercapnia group (n = 8). Although there was no significant difference in blood pressure response to laryngoscopy and endotracheal intubation between normocapnic and hypercapnic groups, heart rate response was significantly attenuated in hypercapnic group and the latent period between the start of laryngoscopy and the onset of increase in heart rate was significantly longer in hypercapnic group. Our results suggest that hypercapnia exerts inhibitory influence on heart rate responses to laryngoscopy and endotracheal intubation.