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To characterize the association of longitudinal changes in maternal anthropometric measures with neonatal anthropometry and to assess to what extent late-gestational changes in maternal anthropometry are associated with neonatal body composition.
In a prospective cohort of pregnant women, maternal anthropometry was measured at six study visits across pregnancy and after birth, neonates were measured and fat and lean mass calculated. We estimated maternal anthropometric trajectories and separately assessed rate of change in the second (15–28 weeks) and third trimester (28–39 weeks) in relation to neonatal anthropometry. We investigated the extent to which tertiles of third-trimester maternal anthropometry change were associated with neonatal outcomes.
Women were recruited from twelve US sites (2009–2013).
Non-obese women with singleton pregnancies (n 2334).
A higher rate of increase in gestational weight gain was associated with larger-birth-weight infants with greater lean and fat mass. In contrast, higher rates of increase in maternal anthropometry measures were not associated with infant birth weight but were associated with decreased neonatal lean mass. In the third trimester, women in the tertile of lowest change in triceps skinfold (−0·57 to −0·06 mm per week) had neonates with 35·8 g more lean mass than neonates of mothers in the middle tertile of rate of change (−0·05 to 0·06 mm per week).
The rate of change in third-trimester maternal anthropometry measures may be related to neonatal lean and fat mass yet have a negligible impact on infant birth weight, indicating that neonatal anthropometry may provide additional information over birth weight alone.
Incorporating consumer perspectives into mental health services design is important in working to deliver recovery-oriented care. One of the challenges faced in mental health rehabilitation services is limited consumer engagement with the available support. Listening to consumers’ expectations of mental health services, and what they hope to achieve, provides an opportunity to examine the alignment between existing services and the priorities and preferences of the people who use them. We explored consumer understandings and expectations of three recovery-oriented community-based residential mental-health rehabilitation units using semi-structured interviews; two of these units were trialling a staffing model integrating peer support with clinical care.
Twenty-four consumers completed semi-structured interviews with an independent interviewer during the first 6 weeks of their stay at the rehabilitation unit. Most participants had a primary diagnosis of schizophrenia or a related psychotic disorder (87%). A pragmatic approach to grounded theory guided the analysis, facilitating identification of content and themes, and the development of an overarching conceptual map.
The rehabilitation units were considered to provide a transformational space and a transitional place. The most common reason given for engagement was housing insecurity or homelessness rather than the opportunity for rehabilitation engagement. Differences in expectations did not emerge between consumers entering the clinical and integrated staffing model sites.
Consumers understand the function of the rehabilitation service they are entering. However, receiving rehabilitation support may not be the key driver of their attendance. This finding has implications for promoting consumer engagement with rehabilitation services. The absence of differences between the integrated and clinical staffing models may reflect the novelty of the rehabilitation context. The study highlights the need for staff to find better ways to increase consumer awareness of the potential relevance of evidence-based rehabilitation support to facilitating their recovery.
No previous research has investigated the neural correlates of vocabulary acquisition in second language learners of sign language. The present study investigated whether poor vocabulary knowledge engaged similar prefrontal lexico-semantic regions as seen in unimodal L2 learners. Behavioral improvements in vocabulary knowledge in a cohort of M2L2 learners were quantified. Results indicated that there is significant increase in vocabulary knowledge after one semester, but stabilized in the second semester. A longitudinal fMRI analysis was implemented for a subset of learners who were followed for the entire 10 months during initial sign language acquisition. The results indicated that learners who had poor sign vocabulary knowledge consistently showed greater activation in regions involved in motor simulation, salience, biological motion and spatial processing, and lexico-semantic retrieval. In conclusion, poor vocabulary knowledge requires greater engagement of modality-independent and modality-dependent regions, which could account for behavioral evidence of difficulty in visual phonology processing.
Understanding how language modality (i.e., signed vs. spoken) affects second language outcomes in hearing adults is important both theoretically and pedagogically, as it can determine the specificity of second language (L2) theory and inform how best to teach a language that uses a new modality. The present study investigated which cognitive-linguistic skills predict successful L2 sign language acquisition. A group (n = 25) of adult hearing L2 learners of American Sign Language underwent a cognitive-linguistic test battery before and after one semester of sign language instruction. A number of cognitive-linguistic measures of verbal memory, phonetic categorization skills, and vocabulary knowledge were examined to determine whether they predicted proficiency in a multiple linear regression analysis. Results indicated that English vocabulary knowledge and phonetic categorization skills predicted both vocabulary growth and self-rated proficiency at the end of one semester of instruction. Memory skills did not significantly predict either proficiency measures. These results highlight how linguistic skills in the first language (L1) directly predict L2 learning outcomes regardless of differences in L1 and L2 language modalities.
This study investigated the structure of the bimodal bilingual lexicon. In the cross-modal priming task nonnative sign language learners heard an English word (e.g., keys) and responded to the lexicality of a signed target: an underlying rhyme (e.g., cheese) or a sign neighbor of that word (e.g., paper). The results indicated that rhyme words were retrieved more quickly and the L2 neighbors were faster for beginner learners. An item analysis also indicated that semantics did not facilitate neighbor retrieval and high frequency signs were retrieved more quickly. The AX discrimination task showed that learners focus on handshape and movement parameters and discriminate equally. The interlanguage dynamics play an important role in which phonological parameters are used and the spread of activation over time. A nonselective, integrated model of the bimodal bilingual lexicon is proposed such that lateral connections are weakened over time and handshape parameter feeds most of the activation to neighboring signs as a function of system dynamics.
As we scrutinize the landforms that surround us, we develop a sense of appreciation for the multitude of processes that shaped our planet. At the outset, we may think it is improbable that, out of this chaotic combination of physical processes, there could emerge any sense of abiding order. Nevertheless, we have come to appreciate during the preceding decades that the collective interaction of many different ingredients, as demonstrated by the Earth, yields manifestations of a new class of behavior which we refer to as “nonlinearity.” It is important that we distinguish between the nonlinearity that we associate with the kinds of differential equations that we have discussed – i.e. the presence of terms that are of higher order than linear – from the collective behavior and self-organization that we sometimes observe. We reviewed this collective behavior in the context of solitary waves. Another aspect sometimes maintained by nonlinearity has roots in geometry and, as a consequence, influences in a profound way a variety of physical systems. Later, we shall survey features of percolation and fractal geometry as illustrations of this. We observed earlier how a “cascade” picture for energy transfer between different length scales at the same rate, as a form of self-organization, could help us understand turbulence and the emergence of power-law scalings. Perhaps this and other kinds of nonlinearity can help us understand the nature of earthquakes.
Most of this book, in its pursuit of studying continuum mechanics, focused on linearized problems and their decomposition into relatively simple superpositions of solutions. Real-world problems, in contrast, are much more complicated. The calculation of exact solutions to linearized problems in the face of complicated geometries very often can become computationally intensive. Further, realistic problems often introduce substantial nonlinearity – this is especially true in applications involving fluids – rendering such calculations inaccurate, if not incorrect. Moreover, the application of computational methods, however, is not trivial. Computer arithmetic, unlike computer algebra such as that performed by Mathematica and Maple, is executed with a finite number of digits of accuracy (Higham, 2002). Typically, there are 16 digits in double precision arithmetic in programming languages such as C++ and FORTRAN 95, but as great as 25 in MATLAB. Continuum mechanical problems involving matrices, particularly those of large rank, can lose many digits of accuracy due to ill-conditioned matrices. Adding to the arithmetic limitations of computers, the more common tasks of solving nonlinear ordinary and, especially, partial differential equations of continuum mechanics present a formidable issue. The operative differential equations were formulated in the mathematical limit of certain differential quantities going to zero, i.e. infinitesimal quantities that emerge in the evaluation of derivatives. Computers, on the other hand, only work in the realm of the finite quantities.
We begin by examining the nature of forces on continuous media. We will pursue this theme later by examining material response. This topic is a truly venerable one with significant references made by Newton (Chandrasekhar, 1995) and many others before and after. Early treatments of this topic employ modes of notation very similar to ours, but largely focus on two-dimensional problems since much of the algebra reduces to that associated with quadratic equations. We will show that in three dimensions, the algebraic problem corresponds to a cubic polynomial with real roots which can be easily determined by analytical means. A medium is homogeneous if its properties are the same everywhere.
Homogeneity, however, can be of two types: regular or random. A regular homogeneous medium has the same underlying character everywhere, e.g. a piece of metal whose atoms are organized in a lattice. A random homogeneous medium has the same underlying statistical distribution of properties, but may lack regularity. For example, a rock composed of many different grains cemented together can be said to be homogeneous if the statistical properties of the mix do not vary. A homogeneous material is also said to be isotropic, i.e. looks the same in all directions. The material looks the same because it is the same. However, an isotropic material is not necessarily homogeneous. For example, the Earth appears to be (crudely) isotropic as viewed from its center but the core, mantle, and lithosphere are very distinct from each other.
This book is the outcome of an introductory graduate-level course that I have given at the University of California, Los Angeles for a number of years as part of our program in Geophysics and Space Physics. Our program is physics-oriented and draws many of its students from the ranks of undergraduate physics and, sometimes, mathematics majors, in addition to geophysics and occasionally geology majors. Accordingly, this text approaches the subject by promoting a physics-based understanding of the basic principles with a relatively rigorous mathematical approach. Since the needs of this course were rather unique, blending concepts in physics and mathematics with the Earth sciences, I approached teaching the subject by drawing on many sources in developing the necessary material. (Throughout this volume, I refer to materials that provide more complete treatments of the topics which we only have time to overview.) In contrast to other sources, I wanted this course to treat not only classical methods but survey some of the ideas emerging in the geosciences that were drawn directly from current ideas in physics, especially nonlinear dynamics. Over time, the material developed more coherence and my lecture notes for this academic quarter-long course evolved into this text.
The subject of continuum mechanics is predicated on the notion that many natural phenomena have a fundamentally smooth, continuous nature. This constitutes the basis for solid and fluid mechanics, major components of this course.
Fluid mechanics occupies an important niche in the study of the Earth. Fluid motions describe the behavior of the interior of this and other planets, as well as the motion of our respective oceans and atmospheres. Remarkably, fluid behavior can manifest some truly amazing properties. Van Dyke (1982) provides a visual compendium of these behaviors, describing the richness of flow patterns that can emerge. The study of fluid mechanics remains a venerable topic and there are a number of excellent textbooks available. Batchelor (1967) provides an authoritative introduction to the subject from the perspective of an applied mathematician, while Landau and Lifshitz (1987) does so from the viewpoint of theoretical physicists. Faber (1995) provides a modern treatment which is encyclopedic in scope but remains a relatively easy read. Fowler (2011) has published an encyclopedic volume addressing many flow problems encountered in geophysics.
Owing to their intrinsic nature, fluids can respond rather dramatically to subtle, almost imperceptible changes in their environment. We now appreciate that sensitivity to an initial set of conditions is the hallmark of chaos. Indeed, thermal convection is often cited as a source of chaos (Drazin, 1992) and the Lorenz model, a skeletal description of a fluid heated from below, as is the case in earth's atmosphere and mantle, has become the paradigm for chaotic behavior. The Lorenz model consists of three coupled ordinary differential equations (Strogatz, 1994; Drazin, 1992).