Failure to Recover from Proactive Semantic Interference Differentiates Amnestic Mild Cognitive Impairment and PreMCI from Normal Aging after Adjusting for Initial Learning Ability

Background: There is increasing evidence that the failure to recover from proactive semantic interference (frPSI) may be an early cognitive marker of preclinical Alzheimer’s disease (AD). However, it is unclear whether frPSI effects reflect deficiencies in an individual’s initial learning capacity versus the actual inability to learn new semantically related targets. Objective: The current study was designed to adjust for learning capacity and then to examine the extent to which frPSI, proactive semantic interference (PSI) and retroactive semantic interference (RSI) effects could differentiate between older adults who were cognitively normal (CN), and those diagnosed with either Pre-Mild Cognitive Impairment (PreMCI) or amnestic MCI (aMCI). Methods: We employed the LASSI-L cognitive stress test to examine frPSI, PSI and RSI effects while simultaneously controlling for the participant’s initial learning capacity among 50 CN, 35 aMCI, and 16 PreMCI participants who received an extensive diagnostic work-up. Results: aMCI and PreMCI participants showed greater frPSI deficits (50% and 43.8% respectively) compared to only 14% of CNparticipants. PSI effects were observed for aMCI but not PreMCI participants relative to their CN counterparts. RSI failed to differentiate between any of the study groups. Conclusion: By using participants as their own controls and adjusting for overall learning and memory, it is clear that frPSI deficits occur with much greater frequency in individuals at higher risk for Alzheimer’s disease (AD), and likely reflect a failure of brain compensatory mechanisms.Fil: Curiel, Rosie E.. University of Miami; Estados UnidosFil: Crocco, Elizabeth A.. University of Miami; Estados UnidosFil: Raffo, Arlene. University of Miami; Estados UnidosFil: Guinjoan, Salvador Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Nemeroff, Charles B.. University of Miami; Estados UnidosFil: Penate, Ailyn. Mount Sinai Medical Center; Estados Unidos. University of Miami; Estados UnidosFil: Piña, Daema. University of Miami; Estados UnidosFil: Loewenstein, David A.. Mount Sinai Medical Center; Estados Unidos. University of Miami; Estados Unido

A disk census for the nearest group of young stars: Mid-infrared observations of the TW Hydrae Association

A group of young, active stars in the vicinity of TW Hydrae has recently been identified as a possible physical association with a common origin. Given its proximity ($\sim$50 pc), age ($\sim$10 Myr) and abundance of binary systems, the TW Hya Association is ideally suited to studies of diversity and evolution of circumstellar disks. Here we present mid-infrared observations of 15 candidate members of the group, 11 of which have no previous flux measurements at wavelengths longer than 2$\mu$m. We report the discovery of a possible 10$\mu$m excess in CD -33$^{\circ}$7795, which may be due to a circumstellar disk or a faint, as yet undetected binary companion. Of the other stars, only TW Hya, HD 98800, Hen 3-600A, and HR 4796A -- all of which were detected by IRAS -- show excess thermal emission. Our 10$\mu$m flux measurements for the remaining members of the Association are consistent with photospheric emission, allowing us to rule out dusty inner disks. In light of these findings, we discuss the origin and age of the TW Hya Association as well as implications for disk evolution timescales.Comment: 10 pages and 1 PostScript figure, accepted for publication in The Astrophysical Journal Letter

Water retention properties of two deep Tertiary clay formations within the context of radioactive waste disposal.

Belgium investigates the design for disposal of its ‘High-Level Radioactive Waste’ in two deep clay formations; the Boom clay at Mol, considered the reference host formation, and Ypresian clay at Kallo as the alternative one. The water retention properties of these deep low-porosity formations have been investigated for two main reasons. High suctions develop as a consequence of sample retrieval (at depths between 223 and 350 m), which affect the hydro-mechanical response of these materials, especially at low stress levels. In addition, water retention properties have also been studied to better assess possible desaturation effects due to venting of the disposal facility galleries. After a description of their main properties at intact state and their microstructural features (pore size distributions), the water retention properties of both clays covering a wide suction range and using different complementary techniques are presented and discussed.Peer ReviewedPostprint (published version

Thermo-Hydro-Mechanical Behaviour of Ypresian Clay

Deep geological disposal solution of high-level and long-lived radioactive waste has been internationally recognised as the preferred option. On this regard, Belgium investigates two deep clay formations; the Boom clay at Mol located at around 220 m deep, considered the reference host formation, and recently the Ypresian clay located at around 500 m deep, considered as the alternative one. The main objective of this research is to perform a thermo-hydro-mechanical characterisation of Ypresian clay by a comprehensive experimental program, carried out on undisturbed samples taken from Kallo borehole (370 m deep). The characterisation program comprised laboratory classification tests, initial total suction and water retention curves (with chilled-mirror dew-point psychrometer), X-ray diffraction, small-strain shear stiffness properties at different orientations (parallel and perpendicular to bedding planes), and mercury intrusion porosimetry (pore size distribution curve of the intact material). Oedometer tests under saturated conditions using step loading and continuous loading approaches were used to characterise the volume change properties of the intact material (yield stress, pre and post-yield compressibility) at different orientations (loading parallel and perpendicular to bedding planes) and at different temperatures (22 and 80 ºC). The material was put in contact with synthetic water at a vertical total stress of 4 MPa (to restore the in situ stress), and then subjected to drained heating (the material underwent some small contraction on this process). The water permeability properties were determined on constant volume and oedometer cells at different orientations (flow parallel and perpendicular to bedding planes) and temperatures (22, 40, 60 and 80 ºC). Temperature cycling effects on water permeability were also examined at constant vertical stress in oedometer cells. Microstructural changes undergone by the material along the different stress paths followed were analysed by mercury intrusion porosimetry. The microstructural study focused on the double porosity features of the intact material, and how this pore network evolves on loading and heating. A heating pulse and constant volume equipment was calibrated and upgraded, which included the development of new acquisition software, the adaptation of new pore water pressure transducers, and a new controlled-power cartridge heater. Preliminary results of a heating/cooling pulse test were presented and discussed