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

Petrology and stratigraphy of the Kiowa and Dakota Formations (basal Cretaceous), north-central Kansas

Ph. D. University of Kansas, Geology 1966The Kiowa Foundation (formerly Kiowa Shale) of Early Cretaceous age and the Dakota Foundation of Early(?) and Late Cretaceous age have been studied and mapped on a detailed reconnaissance basis in an area encompassing some 3500 square miles (9100 krn2) in north-central Kansas. Mapping was initiated as a means of unravelling the stratigraphy, an understanding of which is essential to sedimentary petrographic studies. Neither formation had previously been mapped extensively despite long standing as rock-stratigraphic units. The Kiowa Formation is not present in the northern part of the area mapped. Both formations have an involved nomenclatural history. The Kiowa Foundation is a heterogeneous assemblage composed largely of olive-weathering gray illitic shale and abundant sandstone. The Foundation rests on the eroded surface of Permian rocks. Along the eastern fringes of its outcrop belt, the Kiowa Formation contains a diagnostic sequence of siltstone underlain by a heterogeneous assemblage of red-mottled and carbonaceous gray to black mudstone and siltstone. The mudstone contains variable amounts of montmorillonite and kaolinite. The siltstone and the underlying assemblage are designated the Longford Member (new name) of the Kiowa Foundation. Above the Longford Member, the Kiowa Formation contains numerous fossils of marine or brackish-water invertebrates. As in the Dakota Formation above, fossil deciduous leaves locally are abundant. The Dakota Formation is subdivided into two members, the Terra Cotta Clay Member below and the Janssen Clay Member above. The Terra Cotta is made up largely of light-gray kaolinitic mudstone and claystone showing abundant red mottles, but it also contains appreciable sandstone. The Janssen is composed chiefly of gray and dark-gray kaolinitic mudstone and claystone, locally abundant sandstone, and scattered beds of lignite. It contains marine and brackish-water fossils near its contact with the overlying Graneros Shale, into which its upper part grades laterally. The Kiowa Formation was deposited in, and near the margins of, the Early Cretaceous sea that transgressed from southwest· to northeast across Kansas. Part of the Longford Member of the Kiowa Formation is thought to have been deposited on the landward side of the shifting shoreline. The upper part of the formation is thought to include regressive deposits, sedimentation of which heralded deposition of the Dakota Formation. The Dakota Formation is mainly an alluvial plain deposit that developed and extended itself southwestward upon relatively rapid withdrawal of the Kiowa sea. Upward changes in the Janssen Clay Member largely reflect the influence of the transgressing sea in which the Graneros Shale was deposited. Sandstone in the Kiowa and Dakota formations is mature and contains as much as 95 percent detrital quartz, quartzite, and chert, and locally contains molds and casts of pelecypods. Conglomeratic sandstone in the Dakota Formation is coarser grained than conglomeratic sandstone in the Kiowa and contains numerous pebbles of penecontemporaneously reworked mudstone and claystone. Heavy mineral assemblages in both formations are similar and contain zircon, tourmaline, and staurolite as major components. The proportion of staurolite decreases upward in passing from the Kiowa Formation to the Janssen Clay Member of the Dakota Formation. Sandstone in both formations is abundantly cross-stratified. Computation of vector-resultant dip bearings of cross-strata in both formations indicates that the regional slope was inclined to the west-southwest. The heavy mineral suite therefore is attributed in part to source areas lying to the east and northeast, mainly Paleozoic or older rocks. The staurolite probably was derived from rocks in the central Appalachian Mountains. Variations in clay mineralogy are attributed to differential transport and sedimentation. Source areas for the clay minerals are thought to have been generally the same for both formations. The contact selected for mapping the Kiowa and Dakota formations is a sharp, consistent boundary that can be used in most of north-central Kansas and in the type area of the Kiowa Foundation in southwestern Kansas. In many places the contact is disconformable

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

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

The impact of space and space-related activities on a local economy. a case study of boulder, colorado. part ii- the income-product accounts

Total impact of space and space related activities on local economy of Boulder, Colorado - income-product account

Efficient algorithms for tensor scaling, quantum marginals and moment polytopes

We present a polynomial time algorithm to approximately scale tensors of any format to arbitrary prescribed marginals (whenever possible). This unifies and generalizes a sequence of past works on matrix, operator and tensor scaling. Our algorithm provides an efficient weak membership oracle for the associated moment polytopes, an important family of implicitly-defined convex polytopes with exponentially many facets and a wide range of applications. These include the entanglement polytopes from quantum information theory (in particular, we obtain an efficient solution to the notorious one-body quantum marginal problem) and the Kronecker polytopes from representation theory (which capture the asymptotic support of Kronecker coefficients). Our algorithm can be applied to succinct descriptions of the input tensor whenever the marginals can be efficiently computed, as in the important case of matrix product states or tensor-train decompositions, widely used in computational physics and numerical mathematics. We strengthen and generalize the alternating minimization approach of previous papers by introducing the theory of highest weight vectors from representation theory into the numerical optimization framework. We show that highest weight vectors are natural potential functions for scaling algorithms and prove new bounds on their evaluations to obtain polynomial-time convergence. Our techniques are general and we believe that they will be instrumental to obtain efficient algorithms for moment polytopes beyond the ones consider here, and more broadly, for other optimization problems possessing natural symmetries

Exploration adjustment by ant colonies

© 2016 The Authors. How do animals in groups organize their work? Division of labour, i.e. the process by which individuals within a group choose which tasks to perform, has been extensively studied in social insects. Variability among individuals within a colony seems to underpin both the decision over which tasks to perform and the amount of effort to invest in a task. Studies have focused mainly on discrete tasks, i.e. tasks with a recognizable end. Here, we study the distribution of effort in nest seeking, in the absence of new nest sites. Hence, this task is open-ended and individuals have to decide when to stop searching, even though the task has not been completed. We show that collective search effort declines when colonies inhabit better homes, as a consequence of a reduction in the number of bouts (exploratory events). Furthermore, we show an increase in bout exploration time and a decrease in bout instantaneous speed for colonies inhabiting better homes. The effect of treatment on bout effort is very small; however, we suggest that the organization of work performed within nest searching is achieved both by a process of self-selection of the most hard-working ants and individual effort adjustment

Prognostic value of peripheral lymphocyte count in hormone therapy of advanced breast cancer.

Peripheral lymphocyte counts were performed on 41 patients with advanced breast cancer, before starting treatment with oestrogens or androgens. Patients were seen at monthly intervals, and the response to treatment was independently assessed, using the criteria of the British Breast Group. In the patients treated with oestrogens and androgens, the successful responders were found to have significantly higher pre-treatment peripheral lymphocyte counts than the intermediate responders and failures. It is suggested that pre-treatment peripheral lymphocyte counts may have a prognostic value in assessing potential response to hormone therapy in patients with breast cancer

Genetic and epigenetic catalysts in early-life programming of adult cardiometabolic disorders

Evidence has emerged across the past few decades that the lifetime risk of developing morbidities like type 2 diabetes, obesity, and cardiovascular disease may be influenced by exposures that occur in utero and in childhood. Developmental abnormalities are known to occur at various stages in fetal growth. Epidemiological and mechanistic studies have sought to delineate developmental processes and plausible risk factors influencing pregnancy outcomes and later health. Whether these observations reflect causal processes or are confounded by genetic and social factors remains unclear, although animal (and some human) studies suggest that epigenetic programming events may be involved. Regardless of the causal basis to observations of early-life risk factors and later disease risk, the fact that such associations exist and that they are of a fairly large magnitude justifies further research around this topic. Furthermore, additional information is needed to substantiate public health guidelines on lifestyle behaviors during pregnancy to improve infant health outcomes. Indeed, lifestyle intervention clinical trials in pregnancy are now coming online, where materials and data are being collected that should facilitate understanding of the causal nature of intrauterine exposures related with gestational weight gain, such as elevated maternal blood glucose concentrations. In this review, we provide an overview of these concepts