Experimental evidence showing the existence of signal amplification via perturbation of periodic and chaotic orbits in an electronic circuit is presented.
Overview:Patients with insomnia commonly report that unpleasant intrusive thoughts and images prevent them falling asleep. Previous research has documented the topics people with insomnia think about during the pre‐sleep period, but has not yet distinguished between different types of cognitive activity. Given that research relating to the anxiety disorders suggests that different types of cognitive activity, in particular images and verbal worry, are functionally independent, the present study aimed to provide a detailed phenomenological investigation of imagery and verbal thought in insomnia. Design and method:A semi‐structured interview, designed to assess the content and management of pre‐sleep images and verbal thought, was administered to individuals with sleep‐onset insomnia ( N = 34) and good sleepers ( N = 38) immediately following an afternoon nap. During the nap, heart rate and sleep‐onset latency were measured objectively. Results:The insomnia group was more likely than the good sleeper group to report negative images than positive images. The start, direction and stopping of pre‐sleep images was rated as less controllable than pre‐sleep verbal thoughts. Conclusion:Participants disengaged more from images compared with verbal thoughts, and the insomnia patients reported feeling less calm and relaxed at the end of the salient verbal thought compared with the good sleepers.
We present a study of the factors that influence the adsorption of CO on a Pt(111) surface. Coadsorption of O and OH, as well as alloying of Ru is investigated. We find that coadsorption of CO either with O or OH on Pt weakens the strength of the Pt-CO bond, through a largely strain mediated interaction. Alloying Pt with Ru on the surface only slightly enhances the adsorption energy of CO relative to that of pure Pt. However, once Ru is oxidized by O or OH the adsorption energy of CO on a neighboring Pt is dramatically reduced. These findings as well as some information on the competitive adsorption behavior are discussed in the context of designing CO-tolerant Pt catalysts.
Second and third generation silylalkoxy-terminated carbosilane dendrimers have been used to make high surface area xerogels via an acid-catalyzed sol-gel protocol. These xerogels are micro- and mesoporous and contain a high degree of −OH functionality. An unexpected trend with respect to dendrimer generation and xerogel surface area is described. These xerogels may have applications as (for example) catalyst supports and porous membranes.
We investigate the class of so-called epidemic algorithms that are commonly \nused for the lazy transmission of\nupdates to distributed copies of a database. These algorithms use a simple \nrandomized communication\nmechanism to ensure robustness. Suppose $n$ players communicate in parallel \nrounds in each of which every\nplayer calls a randomly selected communication partner. In every round, players \ncan generate rumors\n(updates) that are to be distributed among all players. Whenever communication \nis established between two\nplayers, each one must decide which of the rumors to transmit. The major \nproblem (arising due to the\nrandomization) is that players might not know which rumors their partners have \nalready received. For\nexample, a standard algorithm forwarding each rumor from the calling to the \ncalled players for $\\Theta(\\ln\nn)$ rounds needs to transmit the rumor $\\Theta(n \\ln n)$ times in order to \nensure that every player finally\nreceives the rumor with high probability. \n\nWe investigate whether such a large communication overhead is inherent to \nepidemic algorithms. On the\npositive side, we show that the communication overhead can be reduced \nsignificantly. We give an algorithm\nusing only $O(n \\ln\\ln n)$ transmissions and $O(\\ln n)$ rounds. In addition, we \nprove the robustness of this\nalgorithm, e.g., against adversarial failures. On the negative side, we show \nthat any address-oblivious algorithm\n(i.e., an algorithm that does not use the addresses of communication partners) \nneeds to send $\\Omega(n \\ln\\ln\nn)$ messages for each rumor regardless of the number of rounds. Furthermore, we \ngive a general lower bound\nshowing that time- and communication-optimality cannot be achieved \nsimultaneously using random phone\ncalls, that is, every algorithm that distributes a rumor in $O(\\ln n)$ rounds \nneeds $\\omega(n)$ transmissions.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
This article addresses pragmatic issues regarding the assessment of puberty in research on adolescent health and development. Because pubertal processes have a major effect on physical, psychological, and social development, we posit that the assessment of pubertal status is at least as important as the specification of age for characterizing adolescent participants in research studies. Yet, a sampling of recent literature shows that the majority of publications addressing health and developmental issues in adolescence lack any measure of puberty. A more comprehensive review of 447 articles reporting to have assessed puberty reveals considerable inconsistencies in methods, definitions, and conceptualizations of puberty and its stages, which highlights the need for better standardization. This article provides an in-depth review of existing methods to assess pubertal status and timing and enumerates the relative merits and shortcomings of several approaches. Conceptual and practical guidelines are provided for selecting specific measures to assess puberty with an emphasis placed on the need for these choices to be driven by the specific goals of the research.
The Cretaceous−Paleogene (K-Pg) extinction caused significant environmental upheaval, including the disappearance of non-avian dinosaurs and widespread disruption of ecosystems. The Hell Creek and Fort Union formations in the upper Great Plains of North America preserve a record of environmental change across the K-Pg boundary (KPB). Sedimentological studies suggest that the Hell Creek Formation represents a well-drained floodplain, with increased standing water leading to the formation of ponds and peat bogs close to the KPB. This shift has been attributed to the disruption of river systems by short-term extinction-driven flooding in the Western Interior. To test this, we analyze ∼2900 paleocurrent measurements from elongate concretions mapped over ∼5000 km2 in the Hell Creek area of eastern Montana, USA. These measurements, combined with previously published chronostratigraphic constraints, allow us to trace river system evolution over time. Paleocurrents shift from a uniform NW-SE direction to a chaotic and later bimodal pattern ∼400 k.y. after the KPB, but no major shifts occur at the KPB itself. Additionally, we develop a method to identify meandering rivers based on paleocurrent distributions and use it to assess river planform changes. Environmental crises have been suggested to cause transitions from meandering to braided rivers, but we find no evidence of such a change. This suggests that the K-Pg extinction did not significantly disrupt regional drainage or river systems in the Hell Creek area. The results demonstrate the potential of remote sensing for reconstructing paleoriver dynamics and suggest that some river systems may be stable across mass extinction events.
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