Thermodynamic anomalies in a lattice model of water: Solvation properties

We investigate a lattice-fluid model of water, defined on a 3-dimensional body-centered cubic lattice. Model molecules possess a tetrahedral symmetry, with four equivalent bonding arms. The model is similar to the one proposed by Roberts and Debenedetti [J. Chem. Phys. 105, 658 (1996)], simplified by removing distinction between "donors" and "acceptors". We focus on solvation properties, mainly as far as an ideally inert (hydrophobic) solute is concerned. As in our previous analysis, devoted to neat water [J. Chem. Phys. 121, 11856 (2004)], we make use of a generalized first order approximation on a tetrahedral cluster. We show that the model exhibits quite a coherent picture of water thermodynamics, reproducing qualitatively several anomalous properties observed both in pure water and in solutions of hydrophobic solutes. As far as supercooled liquid water is concerned, the model is consistent with the second critical point scenario.Comment: 12 pages, 9 figures, 1 tabl

Ground State Spin Structure of Strongly Interacting Disordered 1D Hubbard Model

We study the influence of on-site disorder on the magnetic properties of the ground state of the infinite U 1D Hubbard model. We find that the ground state is not ferromagnetic. This is analyzed in terms of the algebraic structure of the spin dependence of the Hamiltonian. A simple explanation is derived for the 1/N periodicity in the persistent current for this model.Comment: 3 pages, no figure

Evolving with the Times: A Push to Legalize Surrogate Parenting Contracts in the State of New York

In opposition to New York’s current prohibition on surrogate parenting contracts, this paper will focus on explaining why, despite its controversial nature, New York should amend its existing law and permit the enforceability of such contracts. Here, common myths surrounding surrogacy will be debunked, arguments made to support the practice of surrogacy will be justified, and an alternative to the current statute will be offered. This alternative statute will propose legislation in a way that can protect New York’s social policy interests while still permitting the enforceability of surrogate parenting contracts

Cluster-variation approximation for a network-forming lattice-fluid model

We consider a 3-dimensional lattice model of a network-forming fluid, which has been recently investigated by Girardi and coworkers by means of Monte Carlo simulations [J. Chem. Phys. \textbf{126}, 064503 (2007)], with the aim of describing water anomalies. We develop an approximate semi-analytical calculation, based on a cluster-variation technique, which turns out to reproduce almost quantitatively different thermodynamic properties and phase transitions determined by the Monte Carlo method. Nevertheless, our calculation points out the existence of two different phases characterized by long-range orientational order, and of critical transitions between them and to a high-temperature orientationally-disordered phase. Also, the existence of such critical lines allows us to explain certain ``kinks'' in the isotherms and isobars determined by the Monte Carlo analysis. The picture of the phase diagram becomes much more complex and richer, though unfortunately less suitable to describe real water.Comment: 10 pages, 9 figures, submitted to J. Chem. Phy

Ecology and Behavior of the Asian Elephant

The Asian elephant was studied in Sri Lanka from 1967 until 1978. Under the sponsorship of the Smithsonian Institution, six zoologists have addressed themselves to an analysis of the behavior and ecology of the Asian elephant over a period of eleven years (Figure 1). Although elephants were studied in all three national parks found in Sri Lanka, the major effort during the last seven years has been concentrated on Gal Oya National Park. Although the Asian elephant shares numerous behavioral traits with those of the African, differences may be noted. It is proposed that the major differences between the two species in terms of population structure, social groupings, and habitat utilization reflect the longer history of the Asian elephant\u27s adaptation to a forest-grassland ecotone. An analysis of feeding rates and competition among the various large herbivores in Gal Oya National Park indicates that at certain seasons of the year, buffalo and elephants may become strong competitors. Interspecific competition among herbivores varies greatly when patterns of resource exploitation are compared among three national parks. The Asian elephant has declined significantly in recent years and may properly be considered a threatened, if not an endangered, species. Conflicts between man and elephant in Asia have a far longer history than elephant-agricultural conflicts which are developing in Africa. The elephant\u27s survival in peninsular India is a tribute to the adaptability of human culture to accommodate another species

Revisiting waterlike network-forming lattice models

In a previous paper [J. Chem. Phys. 129, 024506 (2008)] we studied a 3 dimensional lattice model of a network-forming fluid, recently proposed in order to investigate water anomalies. Our semi-analytical calculation, based on a cluster-variation technique, turned out to reproduce almost quantitatively several Monte Carlo results and allowed us to clarify the structure of the phase diagram, including different kinds of orientationally ordered phases. Here, we extend the calculation to different parameter values and to other similar models, known in the literature. We observe that analogous ordered phases occur in all these models. Moreover, we show that certain "waterlike" thermodynamic anomalies, claimed by previous studies, are indeed artifacts of a homogeneity assumption made in the analytical treatment. We argue that such a difficulty is common to a whole class of lattice models for water, and suggest a possible way to overcome the problem.Comment: 13 pages, 12 figure

Numerical calculation of the combinatorial entropy of partially ordered ice

Using a one-parameter case as an example, we demonstrate that multicanonical simulations allow for accurate estimates of the residual combinatorial entropy of partially ordered ice. For the considered case corrections to an (approximate) analytical formula are found to be small, never exceeding 0.5%. The method allows one as well to calculate combinatorial entropies for many other systems.Comment: Extended version: 7 pages, 10 figures (v1 is letter-type version

Multiphoton path entanglement by non-local bunching

Multiphoton path entanglement is created without applying post-selection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the non-local bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers.Comment: 4 pages, 5 figures, published versio