North Carolina State University

About: North Carolina State University is a education organization based out in Raleigh, North Carolina, United States. It is known for research contribution in the topics: Population & Thin film. The organization has 44161 authors who have published 101744 publications receiving 3456774 citations. The organization is also known as: NCSU & North Carolina State University at Raleigh.

Abstract functional-differential equations and reaction-diffusion systems

Abstract: FUNCTIONAL DIFFERENTIAL EQUATIONS AND REACTION-DIFFUSION SYSTEMS R. H. MARTIN, JR. AND H. L. SMITH ABSTRACT. Several fundamental results on the existence and behavior of solutions to semilinear functional differential equations are developed in a Banach space setting. The ideas are applied to reaction-diffusion systems that have time delays in the nonlinear reaction terms. The techniques presented here include differential inequalities, invariant sets, and Lyapunov functions, and therefore they provide for a wide range of applicability. The results on inequalities and especially strict inequalities are new even in the context of semilinear equations whose nonlinear terms do not contain delays. Several fundamental results on the existence and behavior of solutions to semilinear functional differential equations are developed in a Banach space setting. The ideas are applied to reaction-diffusion systems that have time delays in the nonlinear reaction terms. The techniques presented here include differential inequalities, invariant sets, and Lyapunov functions, and therefore they provide for a wide range of applicability. The results on inequalities and especially strict inequalities are new even in the context of semilinear equations whose nonlinear terms do not contain delays. Suppose Q is a bounded domain in RN with aQ smooth and A is the Laplacian operator on Q. Also, let m be a positive integer, z a positive number, and f = (fi)m a continuous, bounded function from [0, xc] x Q x C([-z, 0])m into Rm where C([-T, 0]) is the space of continuous functions from [-z, 0] into R. The purpose of this paper is to apply abstract results for semilinear functional differential equations in Banach spaces to reactiondiffusion systems with time delays having the form a tu(x, t) = diAu' (x, t) + ?i(t, x, ut(x, *)), t>a, xeQ, i=1,...,m, (RDD) ai(x)ui(x, t) + au i(x, t) = ,81(x, t), t > a , x EaQ u'(x , a + 0) = X'(x , 0) 5 -T 0, di > 0, and ca:Q * [0,o ) is C' and ,i:Q x [0, oo) R is C2. Here an is the outward normal derivative on aQ and if di = 0 it is assumed that no boundary conditions are specified for this i. Also, tu'(x, t) denotes the partial with respect to t, whereas ut(x, *) denotes the member of C([-z, 0]) defined by 0 -u(x, t + 0) = (u'(x, t + 0))M. Our techniques provide basic existence criteria, but the main point is that they can also be effectively applied to obtain estimates for solutions, especially Received by the editors October 7, 1987 and, in revised form, October 7, 1988. 1980 Mathematics Subject Classification (1985 Revision). Primary 35R10, 34K30.

The deep evolution of metazoan microRNAs

Abstract: microRNAs (miRNAs) are approximately 22-nucleotide noncoding RNA regulatory genes that are key players in cellular differentiation and homeostasis. They might also play important roles in shaping metazoan macroevolution. Previous studies have shown that miRNAs are continuously being added to metazoan genomes through time, and, once integrated into gene regulatory networks, show only rare mutations within the primary sequence of the mature gene product and are only rarely secondarily lost. However, because the conclusions from these studies were largely based on phylogenetic conservation of miRNAs between model systems like Drosophila and the taxon of interest, it was unclear if these trends would describe most miRNAs in most metazoan taxa. Here, we describe the shared complement of miRNAs among 18 animal species using a combination of 454 sequencing of small RNA libraries with genomic searches. We show that the evolutionary trends elucidated from the model systems are generally true for all miRNA families and metazoan taxa explored: the continuous addition of miRNA families with only rare substitutions to the mature sequence, and only rare instances of secondary loss. Despite this conservation, we document evolutionary stable shifts to the determination of position 1 of the mature sequence, a phenomenon we call seed shifting, as well as the ability to post-transcriptionally edit the 5' end of the mature read, changing the identity of the seed sequence and possibly the repertoire of downstream targets. Finally, we describe a novel type of miRNA in demosponges that, although shows a different pre-miRNA structure, still shows remarkable conservation of the mature sequence in the two sponge species analyzed. We propose that miRNAs might be excellent phylogenetic markers, and suggest that the advent of morphological complexity might have its roots in miRNA innovation.

In-Sample or Out-of-Sample Tests of Predictability: Which One Should We Use?

Abstract: It is widely known that significant in-sample evidence of predictability does not guarantee significant out-of-sample predictability. This is often interpreted as an indication that in-sample evidence is likely to be spurious and should be discounted. In this paper, we question this interpretation. Our analysis shows that neither data mining nor dynamic misspecification of the model under the null nor unmodelled structural change under the null are plausible explanations of the observed tendency of in-sample tests to reject the no-predictability null more often than out-of-sample tests. We provide an alternative explanation based on the higher power of in-sample tests of predictability in many situations. We conclude that results of in-sample tests of predictability will typically be more credible than results of out-of-sample tests.

Molecular Memories That Survive Silicon Device Processing and Real-World Operation

Abstract: If molecular components are to be used as functional elements in place of the semiconductor-based devices present in conventional microcircuitry, they must compete with semiconductors under the extreme conditions required for processing and operating a practical device. Herein, we demonstrate that porphyrin-based molecules bound to Si(100), which exhibit redox behavior useful for information storage, can meet this challenge. These molecular media in an inert atmosphere are stable under extremes of temperature (400°C) for extended periods (approaching 1 hour) and do not degrade under large numbers of read-write cycles (10 12 ).

Competitive Priorities in Operations Management

Abstract: Identifying manufacturers' competitive priorities has long been considered a key element in manufacturing strategy research However, relatively little effort has been devoted to measurement of these constructs in published research In this study we develop scales for commonly accepted competitive priorities, cost importance, quality importance, delivery-time importance, and flexibility importance We assess how well the scales capture the constructs that they represent using data collected from 114 manufacturing plants in the United States The findings suggest that the instrument developed can provide reliable data and that the constructs measured are valid In addition, comparisons between pairs of informants representing the same business indicate that the perceptual measures of competitive priorities are as reliable as point estimates of routine, seemingly objective information