The Portevin-Le Chatelier Effect in Nickel-Base Superalloys: Origins, Consequences and Comparison to Strain Ageing in Other Alloy Systems

Dynamic Strain Ageing (DSA) has reached widespread acceptance since its proposal in the 1940’s as the mechanism behind the Portevin-Le Chatelier effect in ferritic steels. However, it remains an open question as to whether the classical mechanism can be extended to Face-Centred Cubic (FCC) alloys, including nickel-based superalloys, as often implicitly assumed. Given the historical link between serrated flow and loss of ductility in steels, understanding such consequences in superalloys used in key components of a jet engine demands attention. This review compares plastic instabilities in superalloys to those in ferritic steels, including the effects of temperature, strain rate, compositional, microstructural and extrinsic testing parameters on the extent of serrated flow and consequences on mechanical properties. Outstanding issues are discussed in detail, relating both to the lack of a complete experimental argument depicting the origins of serrated flow and different serration ‘Types’, as well as the inability of current predictive models to fully account for multiscale experimental observations. Proposed explanations for plastic instabilities in FCC alloys are discussed, including but not limited to classical DSA, with the aim to guide future experiments to elucidate the origins of serrated flow across length scales and improve key properties such as fatigue life

Matrix Optimization of ZnO for Mass Spectrometry Imaging of Small Neurochemicals in Rat and Mouse Brain Tissue

Testing experimental parameters in order to optimize ZnO nanoparticles as a matrix for low molecular weight neurochemicals in rat and mouse brain tissue

Exact solution of the Schrodinger equation with the spin-boson Hamiltonian

We address the problem of obtaining the exact reduced dynamics of the spin-half (qubit) immersed within the bosonic bath (enviroment). An exact solution of the Schrodinger equation with the paradigmatic spin-boson Hamiltonian is obtained. We believe that this result is a major step ahead and may ultimately contribute to the complete resolution of the problem in question. We also construct the constant of motion for the spin-boson system. In contrast to the standard techniques available within the framework of the open quantum systems theory, our analysis is based on the theory of block operator matrices.Comment: 9 pages, LaTeX, to appear in Journal of Physics A: Mathematical and Theoretica

p-adic Cellular Neural Networks

In this article we introduce the p-adic cellular neural networks which are mathematical generalizations of the classical cellular neural networks (CNNs) introduced by Chua and Yang. The new networks have infinitely many cells which are organized hierarchically in rooted trees, and also they have infinitely many hidden layers. Intuitively, the p-adic CNNs occur as limits of large hierarchical discrete CNNs. More precisely, the new networks can be very well approximated by hierarchical discrete CNNs. Mathematically speaking, each of the new networks is modeled by one integro-differential equation depending on several p-adic spatial variables and the time. We study the Cauchy problem associated to these integro-differential equations and also provide numerical methods for solving them

p-adic cellular neural networks: Applications to image processing

The p-adic cellular neural networks (CNNs) are mathematical generalizations of the neural networks introduced by Chua and Yang in the 80s. In this work we present two new types of -adic CNNs that can perform computations with real data, and whose dynamics can be understood almost completely. The first type of networks are edge detectors for grayscale images. The stationary states of these networks are organized hierarchically in a lattice structure. The dynamics of any of these networks consists of transitions toward some minimal state in the lattice. The second type is a new class of reaction–diffusion networks. We investigate the stability of these networks and show that they can be used as filters to reduce noise, preserving the edges, in grayscale images polluted with additive Gaussian noise. The networks introduced here were found experimentally. They are abstract evolution equations on spaces of real-valued functions defined in the p-adic unit ball for some prime number p. In practical applications the prime p is determined by the size of image, and thus, only small primes are used. We provide several numerical simulations showing how these networks work

Seascape Genetics: A Coupled Oceanographic-Genetic Model Predicts Population Structure of Caribbean Corals

SummaryPopulation genetics is a powerful tool for measuring important larval connections between marine populations [1–4]. Similarly, oceanographic models based on environmental data can simulate particle movements in ocean currents and make quantitative estimates of larval connections between populations possible [5–9]. However, these two powerful approaches have remained disconnected because no general models currently provide a means of directly comparing dispersal predictions with empirical genetic data (except, see [10]). In addition, previous genetic models have considered relatively simple dispersal scenarios that are often unrealistic for marine larvae [11–15], and recent landscape genetic models have yet to be applied in a marine context [16–20]. We have developed a genetic model that uses connectivity estimates from oceanographic models to predict genetic patterns resulting from larval dispersal in a Caribbean coral. We then compare the predictions to empirical data for threatened staghorn corals. Our coupled oceanographic-genetic model predicts many of the patterns observed in this and other empirical datasets; such patterns include the isolation of the Bahamas and an east-west divergence near Puerto Rico [3, 21–23]. This new approach provides both a valuable tool for predicting genetic structure in marine populations and a means of explicitly testing these predictions with empirical data (Figure 1)

Hydraulic Relations and Water Use of Mediterranean Ornamental Shrubs in Containers

A detailed, species-specific comprehension of plant water behavior can be a central tool to improve water management in nursery production and irrigated landscapes. Potted plants of Nerium oleander, Pittosporum tobira, and Ligustrum japonicum 'Texanum' were exposed to controlled increasing drought conditions in greenhouse. Water use, gas exchange, and foliar thermoregulation were monitored along the trial. N. oleander showed the most efficient response to increasing water stress, maintaining high levels of gas exchange and evapotranspiration rate during the whole trial, whereas L. japonicum emerged as the most sensitive species, with a significant drop in physiological performances already from the second day. The more aggressive water behavior of N. oleander can be compared to the one of anisohydric plants, whereas L. japonicum displays an isohydric strategy. P. tobira showed intermediate characteristics between the two other species. This work comes to provide useful tools for the management of irrigation in plant nursery and for decision making in the use of ornamental shrubs for landscape applications

Quasilocalized gravity without asymptotic flatness

We present a toy model of a generic five-dimensional warped geometry in which the 4D graviton is not fully localized on the brane. Studying the tensor sector of metric perturbation around this background, we find that its contribution to the effective gravitational potential is of 4D type (1/r) at the intermediate scales and that at the large scales it becomes 1/r^{1+alpha}, 0<alpha=< 1 being a function of the parameters of the model (alpha=1 corresponds to the asymptotically flat geometry). Large-distance behavior of the potential is therefore not necessarily five-dimensional. Our analysis applies also to the case of quasilocalized massless particles other than graviton.Comment: 9 pages, 1 figure; to be published in Phys. Rev.

Spanish-English Bilingual Toddlers’ Vocabulary Skills: The role of Caregiver Language Input and Warmth

There is a well-documented link between bilingual language development and the relative amounts of exposure to each language. Less is known about the role of quality indicators of caregiver-child interactions in bilingual homes, including caregiver input diversity, warmth and sensitivity. This longitudinal study examines the relation between caregiver input (lexical diversity, amount), warmth and sensitivity and bilingual toddlers’ subsequent vocabulary outcomes. We video-recorded caregiver-child interactions in Spanish-English Latino homes when toddlers (n = 47) were 18 months of age (M = 18.32 months; SD = 1.02 months). At the 24-month follow-up, we measured children\u27s vocabulary as total vocabulary (English, Spanish combined) as well as within language (Spanish, English). Results revealed that Spanish lexical diversity exposure at 18 months from caregivers was positively associated with children\u27s Spanish and total vocabulary scores at 24 months, while English lexical diversity was positively associated with children\u27s English scores; lexical diversity and amount were highly correlated. Additionally, caregivers’ warmth was positively associated with children\u27s Spanish, English and total vocabulary scores. Together, these factors accounted for substantial variance (30–40%) in vocabulary outcomes. Notably, caregiver input accounted for more variance in single language outcomes than did caregiver warmth, whereas caregiver warmth uniquely accounted for more variance in total vocabulary scores. Our findings extend prior research findings by suggesting that children\u27s dual language development may depend on their exposure to a diverse set of words, not only amount of language exposure, as well as warm interactions with caregivers. A video abstract of this article can be viewed at https://youtu.be/q1V_7fz5wogHighlightsVideo-recorded observations of caregiver-child interactions revealed warmth and high sensitivity from Latino caregivers.Linguistically-detailed analyses of caregiver input revealed wide variation in the diversity of Spanish and English directed at 18-month-old bilingual toddlers.Bilingual toddlers’ vocabulary (single language, total) was positively associated with caregivers’ diverse input and warmth, thus extending prior findings on bilinguals’ amount of language exposure.Findings suggest that caregivers’ lexical diversity explains more variance in bilingual toddlers’ single language outcomes, whereas warmth explains more variance in total vocabulary scores