Pressure-induced polyamorphic transition in the CaAl2O4 glass

In situ high-pressure ultrasonic velocity measurements of CaAl2O4 glass reveal abrupt irreversible discontinuities in the elastic wave velocities at ∼8–10 GPa. Total structure factor and pair distribution functions measured by synchrotron x-ray diffraction show a rapid change in the intermediate range structure attributed to a rearrangement of calcium ions over this narrow pressure region. Atomistic models obtained from molecular dynamics simulations reveal that this intermediate range structure is explained by a transition of Ca–O void radius distribution from a bimodal distribution with peaks at ∼2.1 and ∼2.4 Å to a single distribution centered at ∼2.1 Å. These abrupt structural changes involving the rapid increase in elastic wave velocity are markedly different to the continuous transformations observed in conventional network-forming glasses, such as SiO

Delayed neuronal cell death in brainstem after transient brainstem ischemia in gerbils

<p>Abstract</p> <p>Background</p> <p>Because of the lack of reproducible brainstem ischemia models in rodents, the temporal profile of ischemic lesions in the brainstem after transient brainstem ischemia has not been evaluated intensively. Previously, we produced a reproducible brainstem ischemia model of Mongolian gerbils. Here, we showed the temporal profile of ischemic lesions after transient brainstem ischemia.</p> <p>Results</p> <p>Brainstem ischemia was produced by occlusion of the bilateral vertebral arteries just before their entry into the transverse foramina of the cervical vertebrae of Mongolian gerbils. Animals were subjected to brainstem ischemia for 15 min, and then reperfused for 0 d (just after ischemia), 1 d, 3 d and 7 d (n = 4 in each group). Sham-operated animals (n = 4) were used as control. After deep anesthesia, the gerbils were perfused with fixative for immunohistochemical investigation. Ischemic lesions were detected by immunostaining for microtubule-associated protein 2 (MAP2). Just after 15-min brainstem ischemia, ischemic lesions were detected in the lateral vestibular nucleus and the ventral part of the spinal trigeminal nucleus, and these ischemic lesions disappeared one day after reperfusion in all animals examined. However, 3 days and 7 days after reperfusion, ischemic lesions appeared again and clusters of ionized calcium-binding adapter molecule-1(IBA-1)-positive cells were detected in the same areas in all animals.</p> <p>Conclusion</p> <p>These results suggest that delayed neuronal cell death took place in the brainstem after transient brainstem ischemia in gerbils.</p

Isolation of microorganisms involved in reduction of crystalline iron(III) oxides in natural environments

Reduction of crystalline Fe(III) oxides is one of the most important electron sinks for organic compound oxidation in natural environments. Yet a limited number of isolates makes it difficult to understand physiology and ecological impact of the microorganisms involved. Here, two-staged cultivation was implemented to selectively enrich and isolate crystalline iron(III) reducers in soils and sediments. Firstly, iron reducers were enriched and other untargeted eutrophs were depleted by two-year successive culture on a crystalline ferric iron oxide (i.e., goethite, lepidocrocite, hematite, or magnetite) as electron acceptor. Fifty-eight out of 136 incubation conditions allowed the continued existence of microorganisms as confirmed by PCR amplification. High-throughput Illumina sequencing based on 16S rRNA genes revealed that the enrichment cultures on each of the ferric iron oxides contained bacteria belonging to the Deltaproteobacteria (mainly Geobacteraceae), followed by Firmicutes and Chloroflexi, which also comprised most of the operational taxonomic units (OTUs) identified. The Venn diagrams indicated that the core OTUs enriched with all of the iron oxides were dominant in the Geobacteraceae. Secondly, 38 enrichment cultures including novel microorganisms were transferred to soluble-iron(III) media in order to stimulate proliferation of the enriched iron reducers. Through extinction dilution-culture and single colony isolation, six strains within the Deltaproteobacteria were finally obtained; five strains belonged to the genus Geobacter and one strain to Pelobacter. These isolates had 94.8–98.1% sequence similarities of 16S rRNA genes to cultured relatives. All the isolates were able to grow on acetate and ferric iron but their physiological characteristics differed considerably in terms of growth rate. The results demonstrate the successful enrichment and isolation of novel iron(III) reducers that were able to thrive by reducing highly crystallized ferric irons