University of Rhode Island

About: University of Rhode Island is a education organization based out in Kingston, Rhode Island, United States. It is known for research contribution in the topics: Population & Bay. The organization has 11464 authors who have published 22770 publications receiving 841066 citations. The organization is also known as: URI & Rhode Island College of Agriculture and the Mechanic Arts.

Economic Growth and the Expansion of Urban Land in China

Abstract: This paper aims to demonstrate the relationship between economic growth and the urban core area in order to help urban planners reach a better understanding of the pressures that are leading to cha...

Quantum spin dynamics of the antiferromagnetic linear chain in zero and nonzero magnetic field

Abstract: Spin-dynamical calculations on one-dimensional systems have relied heavily on classical ($s=\ensuremath{\infty}$) theories, despite abundant evidence that quantum effects can be extremely important at low temperatures. We present a new approach to the spin dynamics of the one-dimensional isotropic $s=\frac{1}{2}$ Heisenberg antiferromagnetic (HB AF) which does not involve the many-body techniques usually employed. It is based on analytic Bethe ansatz calculations of excitation energies and densities of states combined with finite-chain calculations of matrix elements. An important feature of our method is the use of rigorous selection rules and the introduction of new selection rules, which are valid for macroscopic systems in a magnetic field. We show that in zero field the dynamical two-spin correlation function ${S}_{\ensuremath{\mu}\ensuremath{\mu}}(q,\ensuremath{\omega})$ at $T=0$ is governed by a two-parameter continuum of spin-wave-type excitations. In nonzero field, the longitudinal component ${S}_{\mathrm{zz}}(q,\ensuremath{\omega})$ and the transverse components ${S}_{\mathrm{xx}}(q,\ensuremath{\omega})\ensuremath{\equiv}{S}_{\mathrm{yy}}(q,\ensuremath{\omega})$ behave quite differently because they are dominated by different continua of excitations. The former is characterized by a lowest excitation branch with a zero-frequency mode moving from the zone boundary ($q=\ensuremath{\pi}$) towards the zone center ($q=0$) as the field increases, whereas the latter is characterized by a lowest branch with a zero frequency mode moving from $q=0 \mathrm{to} \ensuremath{\pi}$ with increasing field. The first part of our work features an approximate analytic expression for ${S}_{\ensuremath{\mu}\ensuremath{\mu}}(q,\ensuremath{\omega})$ at zero temperature and in zero field. Although our expression is not rigorous, exact sum rules are violated only by a small amount, and good agreement exists with the few known exact results. Our studies are extended to nonzero temperatures by placing major reliance on exact finite-chain calculations. Our work was stimulated by recent neutron scattering experiments and is oriented towards experimental comparisons. Our result for the $s=\frac{1}{2}$ integrated intensity is in much better agreement with neutron scattering data on Cu${\mathrm{Cl}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}2N(${\mathrm{C}}_{5}$${\mathrm{D}}_{5}$) (CPC) than the corresponding semiclassical result. Moreover, the spectral-weight distribution in ${S}_{\ensuremath{\mu}\ensuremath{\mu}}(q,\ensuremath{\omega})$ shows increasing asymmetry as $q\ensuremath{\rightarrow}\ensuremath{\pi}$, a quantum effect, again in agreement with more recent neutron scattering data. The second part of our work deals with the effects of an applied magnetic field. We extend the analytic work of Ishimura and Shiba to obtain expressions for the energies and densities of states of the various excitation continua. It is shown that these continua are expected to give rise to multiple structures in the scattering intensity. Our results appear to be in quantitative agreement with preliminary results of a neutron study in CPC in a field of 70 kOe, revealing anomalous scattering intensity peaks. Our results repeatedly demonstrate the inadequacy of classical spin-wave theory for this problem. They call for additional experimental studies on quasi-one-dimensional antiferromagnets to examine other unusual and interesting phenomena predicted by our approach.

Sol-gel glass as a matrix for chemical and biochemical sensing

Abstract: Sol-gel glass is a porous glass-like material produced at low temperatures by the sol-gel technique. Sol-gel glass has been increasingly used as a solid matrix for entrapment of chemical and biochemical agents in sensor development and other applications. This article will provide a brief introduction of sol-gel technique and a thorough up-to-date review of the applications of sol-gel derived glass in chemical and biochemical sensing. The sol-gel sensors reviewed include those for pH, ionic species, gases, and glucose. Sol-gel glasses for entrapment of organic dyes, proteins, enzymes and microbial cells, as well as sol-gel derived selective electrodes, are also reviewed.

The Effects of Postpartum Depression on Maternal-Infant Interaction: A Meta-analysis

Abstract: A meta-analysis of 19 studies was conducted to determine the magnitude of the effect of postpartum depression on maternal-infant interaction during the first year after delivery. Maternal-infant interaction was divided into three subcategories: maternal interactive behavior, infant interactive behavior, and dyadic interactive behavior. Substantive, methodological, and miscellaneous variables were extracted and coded by both the researcher and two research assistants. Combinations were calculated as unweighted, weighted by sample size, and weighted by the quality index score. Effects for maternal interactive behavior ranged from .32 to .36 for the r index, .68 to .78 for the d index, and .33 to .38 for the Fischer's Z. For infant interactive behavior, effects ranged from .35 to .38, .75 to .83, and .37 to .41 for the r, d, and Fisher's Z indexes, respectively. Effects for dyadic interactive behavior ranged from .47 to .50 for the r index, 1.07 to 1.15 for the d index, and .51 to .55 for Fisher's Z. Results of the meta-analysis indicate that postpartum depression has a moderate to large effect on maternal-infant interaction. Nursing interventions for depressed mother-infant dyads during the first year after delivery are addressed.

Non-Graphical Solutions for Cattell’s Scree Test

Abstract: Most of the strategies that have been proposed to determine the number of components that account for the most variation in a principal components analysis of a correlation matrix rely on the analysis of the eigenvalues and on numerical solutions. The Cattell's scree test is a graphical strategy with a nonnumerical solution to determine the number of components to retain. Like Kaiser's rule, this test is one of the most frequently used strategies for determining the number of components to retain. However, the graphical nature of the scree test does not definitively establish the number of components to retain. To circumvent this issue, some numerical solutions are proposed, one in the spirit of Cattell's work and dealing with the scree part of the eigenvalues plot, and one focusing on the elbow part of this plot. A simulation study compares the efficiency of these solutions to those of other previously proposed methods. Extensions to factor analysis are possible and may be particularly useful with many low-dimensional components. Several strategies have been proposed to determine the num- ber of components that account for the most variation in a principal components analysis of a correlation matrix. Most of these rely on the analysis of the eigenvalues of the corre- lation matrix and on numerical solutions. For example, Kaiser's eigenvalue greater than one rule (Guttman, 1954; Kaiser, 1960), parallel analysis (Buja & Eyuboglu, 1992; Horn, 1965; Hoyle & Duvall, 2004), or hypothesis signifi- cance tests, like Bartlett's test (1950), make use of numerical criteria for comparison or statistical significance criteria. Independently of these numerical solutions, Cattell (1966) proposed the scree test, a graphical strategy to determine the number of components to retain. Along with the Kaiser's rule, the scree test is probably the most used strategy and it is included in almost all statistical software dealing with principal components analysis. Unfortunately, it is generally recognized that the graphical nature of the Cattell's scree test does not enable clear decision-making about the number of components to retain. The previously proposed non-graphical solutions for