Adjacency matrix formulation of energy flow in dendrimeric polymers

Dendrimers are synthetic, highly branched polymers with an unusually high density of chromophores. As a result of their extremely high absorption cross-sections for visible light, they represent some of the most promising new materials for energy harvesting. Although the signature of the bonding structure in dendrimers is an essentially fractal geometry, the three-dimensional molecular folding of most higher generation materials results in a chromophore layout that is more obviously akin to concentric spherical shells. The number of chromophores in each shell is a simple function of the distance from the central core. The energy of throughput optical radiation, on capture by any of the chromophores, passes by a multi-step but highly efficient process to the photoactive core. Modeling this crucial migration process presents a number of challenges. It is far from a simple diffusive random walk; each step is subject to an intricate interplay of geometric and spectroscopic features. In this report, the first results of a new approach to the theory is described, developed and adapted from an adjacency matrix formulation. It is shown how this method offers not only kinetic information but also insights into the typical number of steps and the patterns of internal energy flow

Electric-field-induced stress relaxation in alpha-phase poly(vinylidene fluoride) films

The relationship between elastic fatigue and electrical cyclic loading in alpha-phase poly(vinylidene fluoride) films has been investigated. Our experimental studies have shown that the electric-field-induced fatigue behavior can be described by a stress relaxation, which belongs to the Kohlrausch function group, and the corresponding exponent is a modified two-parameter Weibull distribution function.Comment: 3 pages, 3 figure

Spatial and spatiotemporal variation in metapopulation structure affects population dynamics in a passively dispersing arthropod

The spatial and temporal variation in the availability of suitable habitat within metapopulations determines colonization-extinction events, regulates local population sizes and eventually affects local population and metapopulation stability. Insights into the impact of such a spatiotemporal variation on the local population and metapopulation dynamics are principally derived from classical metapopulation theory and have not been experimentally validated. By manipulating spatial structure in artificial metapopulations of the spider mite Tetranychus urticae, we test to which degree spatial (mainland-island metapopulations) and spatiotemporal variation (classical metapopulations) in habitat availability affects the dynamics of the metapopulations relative to systems where habitat is constantly available in time and space (patchy metapopulations). Our experiment demonstrates that (i) spatial variation in habitat availability decreases variance in metapopulation size and decreases density-dependent dispersal at the metapopulation level, while (ii) spatiotemporal variation in habitat availability increases patch extinction rates, decreases local population and metapopulation sizes and decreases density dependence in population growth rates. We found dispersal to be negatively density dependent and overall low in the spatial variable mainland-island metapopulation. This demographic variation subsequently impacts local and regional population dynamics and determines patterns of metapopulation stability. Both local and metapopulation-level variabilities are minimized in mainland-island metapopulations relative to classical and patchy ones

Quantitative Robustness Analysis of Quantum Programs (Extended Version)

Quantum computation is a topic of significant recent interest, with practical advances coming from both research and industry. A major challenge in quantum programming is dealing with errors (quantum noise) during execution. Because quantum resources (e.g., qubits) are scarce, classical error correction techniques applied at the level of the architecture are currently cost-prohibitive. But while this reality means that quantum programs are almost certain to have errors, there as yet exists no principled means to reason about erroneous behavior. This paper attempts to fill this gap by developing a semantics for erroneous quantum while-programs, as well as a logic for reasoning about them. This logic permits proving a property we have identified, called $\epsilon$-robustness, which characterizes possible "distance" between an ideal program and an erroneous one. We have proved the logic sound, and showed its utility on several case studies, notably: (1) analyzing the robustness of noisy versions of the quantum Bernoulli factory (QBF) and quantum walk (QW); (2) demonstrating the (in)effectiveness of different error correction schemes on single-qubit errors; and (3) analyzing the robustness of a fault-tolerant version of QBF.Comment: 34 pages, LaTeX; v2: fixed typo

Breakpoint lead-lag analysis of the last deglacial climate change and atmospheric CO2 concentration on global and hemispheric scales

Antarctic ice core records show that climate change and atmospheric CO2 concentration (aCO(2)) are closely related over the past 800 thousand years. However, the interpretation of their sequential, and hence the causal relationship has long been controversial. In this study, we revisit this long-standing scientific issue based on 88 well-dated high-resolution climate proxy records derived from ice cores, marine deposits, and stalagmites. We composite global and hemispheric stacks of the last deglacial climate index (DCI) using a normalization scheme instead of a more conventional area-weighting and mixing scheme to enable a better detection of temporal variations. Rampfit and Breakfit techniques are employed to detect the trend transitions in each composited DCI series and in the recently constructed centennial-scale aCO(2) over the period from 22 to 9 thousand years before present. We detect a clear lead of DCI change over aCO(2) variation on both global and hemispheric scales at the early stage of the deglaciation, suggesting that the variation of aCO(2) is an internal feedback in Earth's climate system rather than an initial trigger of the last deglacial warming. During the periods of the Bolling-Allerod and the Younger Dryas, the climate system appeared to have been constrained by a fast coupling mechanism between climate change and aCO(2) with no obvious asynchrony. The northern and southern hemispheric DCI stacks exhibit a seesawing pattern that can be linked to the influences of Atlantic meridional overturning circulation (AMOC) strength, revealing an important role of AMOC in regulating the global climate in the course of the last deglaciation

The R&D boundaries of the firm : a problem solving perspective

This paper considers, theoretically and empirically, how different organization modes are aligned to govern the efficient solving of technological problems. The data set is from the Chinese consumer electronics industry. Following the problem solving perspective (PSP) within the knowledge-based view (KBV), we develop and test several PSP and KBV hypotheses, whilst controlling for some relevant transaction cost economics (TCE) and other variables, in an examination of the determinants of the firms’ R&D organization choice. The results show that a firm’s existing knowledge base is the most important explanatory factor. Problem complexity and decomposability are also found to be important, but it is suggested, contrary to the view of PSP, that they are better treated as separate variables, and that equity-based alliances tend to be reserved for the most complex problems

Breakpoint lead-lag analysis of the last deglacial climate change andatmospheric CO2 concentration on global and hemispheric scales

Antarctic ice core records show that climate change and atmospheric CO2 concentration (aCO2) are closely related over the past 800 thousand years. However, the interpretation of their sequential, and hence the causal relationship has long been controversial. In this study, we revisit this long-standing scientific issue based on 88 well-dated high-resolution climate proxy records derived from ice cores, marine deposits, and stalagmites. We composite global and hemispheric stacks of the last deglacial climate index (DCI) using a normalization scheme instead of a more conventional area-weighting and mixing scheme to enable a better detection of temporal variations. Rampfit and Breakfit techniques are employed to detect the trend transitions in each composited DCI series and in the recently constructed centennial-scale aCO2 over the period from 22 to 9 thousand years before present. We detect a clear lead of DCI change over aCO2 variation on both global and hemispheric scales at the early stage of the deglaciation, suggesting that the variation of aCO2 is an internal feedback in Earth&#39;s climate system rather than an initial trigger of the last deglacial warming. During the periods of the B&oslash;lling-Aller&oslash;d and the Younger Dryas, the climate system appeared to have been constrained by a fast coupling mechanism between climate change and aCO2 with no obvious asynchrony. The northern and southern hemispheric DCI stacks exhibit a seesawing pattern that can be linked to the influences of Atlantic meridional overturning circulation (AMOC) strength, revealing an important role of AMOC in regulating the global climate in the course of the last deglaciation.<br /