Reduced task deactivation within regions of the default mode network (DMN) has been frequently reported in Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI). As task deactivation reductions become increasingly used in the study of early AD states, it is important to understand their relationship to atrophy. To address this issue, the present study compared task deactivation...

• Calcium increases Pt-Ge alloy extent by enhancing Ge reducibility. significantly enhances catalyst stability and propylene selectivity. selectively suppresses strong acid sites. Calcium-promoted is less active for coke deactivation, (? d ). Steady state activity increased since Ca decreases ? more than r . The promoting effect of on the catalytic performance Pt 0.5 -Ge 1.5 /Al 2 O 3 during pr...

The fundamentals of catalyst deactivation are presented in this review. The chemico-physical aspects concerning the various deactivation causes (i.e. poisoning, sintering, coking, solid-state transformation, masking, etc.) have been analyzed and discussed, along with the mathematical description of the deactivation phenomena. # 1999 Elsevier Science B.V. All rights

Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key...

hydrogen can be produced for fuel cell applications by using methanol steam reforming reaction. in this article, a method was developed for regeneration of accelerated deactivated methanol-steam-reforming catalyst. successive deactivation–regeneration cycles were studied in a 250 hours test for the first time including 6 regeneration cycles. it is shown that regeneration of the catalyst in dilu...

fischer-tropsch synthesis is a promising route for production of light olefins via co hydrogenation over transition metals. co is one of the most active metals for fischer-tropsch synthesis. some different variables such as preparation parameters and operational factors can strongly affect the selectivity of fischer-tropsch synthesis toward the special products. in the case of preparation varia...

Activation and deactivation of media items plays a fundamental role in the playing of multimedia and time-based hypermedia presentations. Activation and deactivation information thus has to be captured in an underlying document format. In this paper we show that a number of aspects of activation and deactivation information can be captured using both link structures and events in time-based hyp...