Evaluation of a spacecraft nitrogen generator

An experiment was completed to demonstrate that low ammonia concentrations in the product nitrogen stream are possible using the staging concept. Mixtures of nitrogen, hydrogen and ammonia were fed into a temperature controlled packed bed ammonia dissociator. An ammonia concentration of 1.03% in the feed stream was reduced to less than 50 ppm at temperatures greater than or equal to 777K. The actual inlet ammonia concentration to the final nitrogen generation module ammonia dissociation stage was only 0.09%

Antiferromagnetism and Superconductivity in CeRhIn5_5

We discuss recent results on the heavy fermion superconductor CeRhIn$_5$ which presents ideal conditions to study the strong coupling between the suppression of antiferromagnetic order and the appearance of unconventional superconductivity. The appearance of superconductivity as function of pressure is strongly connected to the suppression of the magnetic order. Under magnetic field, the re-entrance of magnetic order inside the superconducting state shows that antiferromagnetism nucleates in the vortex cores. The suppression of antiferromagnetism in CeRhIn$_5$ by Sn doping is compared to that under hydrostatic pressure.Comment: 6 pages, 8 figures, to be published in Proc. Int. Conf. Heavy Electrons (ICHE2010) J. Phys. Soc. Jpn. 80 (2011

Representation of Sound Objects within Early-Stage Auditory Areas: A Repetition Effect Study Using 7T fMRI.

Environmental sounds are highly complex stimuli whose recognition depends on the interaction of top-down and bottom-up processes in the brain. Their semantic representations were shown to yield repetition suppression effects, i. e. a decrease in activity during exposure to a sound that is perceived as belonging to the same source as a preceding sound. Making use of the high spatial resolution of 7T fMRI we have investigated the representations of sound objects within early-stage auditory areas on the supratemporal plane. The primary auditory cortex was identified by means of tonotopic mapping and the non-primary areas by comparison with previous histological studies. Repeated presentations of different exemplars of the same sound source, as compared to the presentation of different sound sources, yielded significant repetition suppression effects within a subset of early-stage areas. This effect was found within the right hemisphere in primary areas A1 and R as well as two non-primary areas on the antero-medial part of the planum temporale, and within the left hemisphere in A1 and a non-primary area on the medial part of Heschl's gyrus. Thus, several, but not all early-stage auditory areas encode the meaning of environmental sounds

Origin of Drastic Change of Fermi Surface and Transport Anomalies in CeRhIn5 under Pressure

The mechanism of drastic change of Fermi surfaces as well as transport anomalies near P=Pc=2.35 GPa in CeRhIn5 is explained theoretically. The key mechanism is pointed out to be the interplay of magnetic order and Ce-valence fluctuations. We show that the antiferromagnetic state with "small" Fermi surfaces changes to the paramagnetic state with "large" Fermi surfaces with huge enhancement of effective mass of electrons with keeping finite c-f hybridization. This explains the drastic change of the de Haas-van Alphen signals. Furthermore, it is also consistent with the emergence of T-linear resistivity simultaneous with the residual resistivity peak at P=Pc in CeRhIn5.Comment: 5 pages, 3 figures, submitted to Journal of Physical Society of Japa

Perplexity – a new predictor of cognitive changes in spoken language? – results of the Interdisciplinary Longitudinal Study on Adult Development and Aging (ILSE)

Abstract: In addition to memory loss, progressive deterioration of speech and language skills is among the main symptoms at the onset of Alzheimer’s disease (AD) as well as in mild cognitive impairment (MCI). Detailed interview analyses demonstrated early symptoms years before the onset of AD/MCI. Automatic speech processing could be a promising approach to identifying underlying mechanisms in larger studies or even support diagnostics. Perplexity as a measure of predictability of text could be a sensitive indicator of cognitive deterioration. Therefore, voice recordings from the Interdisciplinary Longitudinal Study on Adult Development and Aging were analyzed with regard to neuropsychological parameters in participants that develop MCI/AD or remain cognitively healthy. Preliminary results indicate that perplexity predicts severity of cognitive deficits and information processing speed obtained 10–12 years later in participants who developed MCI/AD in contrast to those who stayed healthy. Findings support the heuristic value of research on the diagnostic potential of automatic speech processing

High pressure investigation of the heavy-fermion antiferromagnet U_3Ni_5Al_19

Measurements of magnetic susceptibility, specific heat, and electrical resistivity at applied pressures up to 55 kbar have been carried out on single crystals of the heavy-fermion antiferromagnet U_3Ni_5Al_19, which crystallizes in the Gd_3Ni_5Al_19 orthorhombic structure with two inequivalent U sites. At ambient pressure, a logarithmic T-dependence of the specific heat and T-linear electrical resistivity below 5 K indicates non-Fermi liquid (NFL) behavior in the presence of bulk antiferromagnetic order at T_N=23 K. Electrical resistivity measurements reveal a crossover from non-Fermi liquid to Fermi liquid behavior at intermediate pressures between 46 kbar and 51 kbar, followed by a return to NFL T^{3/2} behavior at higher pressures. These results provide evidence for an ambient pressure quantum critical point and an additional antiferromagnetic instability at P_c=60 kbar.Comment: 12 pages, 5 figure

High pressure phase diagrams of CeRhIn5_5 and CeCoIn5_5 studied by ac calorimetry

The pressure-temperature phase diagrams of the heavy fermion antiferromagnet CeRhIn$_5$ and the heavy fermion superconductor CeCoIn$_5$ have been studied under hydrostatic pressure by ac calorimetry and ac susceptibility measurements using diamond anvil cells with argon as pressure medium. In CeRhIn$_5$, the use of a highly hydrostatic pressure transmitting medium allows for a clean simultaneous determination by a bulk probe of the antiferromagnetic and superconducting transitions. We compare our new phase diagram with the previous ones, discuss the nature (first or second order) of the various lines, and the coexistence of antiferromagnetic order and superconductivity. The link between the collaps of the superconducting heat anomaly and the broadening of the antiferromagnetic transition points to an inhomogeneous appearence of superconductivity below $P_c \approx 1.95$ GPa. Homogeneous bulk superconductivity is only observed above this critical pressure. We present a detailed analysis of the influence of pressure inomogeneities on the specific heat anomalies which emphasizes that the observed broadening of the transitions near $P_c$ is connected with the first order transition. For CeCoIn$_5$ we show that the large specific heat anomaly observed at $T_c$ at ambient pressure is suppressed linearly at least up to 3 GPa