Seriation, Superposition, and Interdigitation: a History of Americanist Graphic Depictions of Culture Change

Histories of Americanist archaeology regularly confuse frequency seriation with a technique for measuring the passage of time based on superposition - percentage stratigraphy - and fail to mention interdigitation as an important component of some percentage-stratigraphic studies. Frequency seriation involves the arrangement of collections so that each artifact type displays a unimodal frequency distribution, but the direction of time\u27s flow must be determined from independent evidence. Percentage stratigraphy plots the fluctuating frequencies of types, but the order of collections is based on their superposition, which in turn illustrates the direction of time\u27s flow. Interdigitation involves the integration of sets of percentage-stratigraphy data from different horizontal proveniences under the rules that (1) the order of superposed collections cannot be reversed and (2) each type must display a unimodal frequency distribution. Ceramic stratigraphy is similar to occurrence seriation, as both focus on the presence-absence of types with limited temporal distributions - index fossils - but the former uses the superposed positions of types to indicate the direction of time\u27s flow, whereas occurrence seriation does not

Addition of Fat to Diets of Lactating Sows. I. Effects on Sow and Pig Performance

Sow energy intake during lactation is an important factor to consider when trying to maximize sow and pig performance. It has been shown that inadequate energy intake during lactation results in decreased litter weaning weight. Poor energy intake during lactation is also thought to result in a reduction in postweaning reproductive performance by extending the period from weaning to rebreeding. This reduction in postweaning performance is typically preceded by the excessive loss of weight and backfat during lactation. One method that has been used to increase sow energy intake, and thus alleviate the problems described above is to add dietary fat. The addition of high concentrations of fat (e.g., 7.5 to 15% of the diet) has been shown to result in increased sow energy intake during lactation, and if consumed for approximately one week before farrowing, increased survival rates for pigs with light birthweights. This article reports the effects of high fat diets on sow lactation performance, litter performance, and sow feed and energy intake. A subsequent article will discuss the effects of added dietary fat on energy intake, meal patterns, and blood hormones and metabolites. A specific objective of this research was to determine the effects of dietary fat on milk production and composition

The Effects of Tallow Addition to the Diets of Lactating Sows on Hormone and Metabolite Concentrations

The metabolic responses of sows fed a corn-soybean meal or a corn-soybean meal-10% tallow diet were measured. The addition of tallow to lactating sows diets had no effect on feed or energy intake. In addition, there were no effects on the concentrations of glucose, non-esterified fatty acids (NEFA), insulin, or glucagon. No differences in either the time spent consuming feed or the number of meals consumed were observed. Finally, no linear association between eating time and area under the curve for insulin was observed for sows consuming either diet. These results show the addition of tallow to lactation diets does not affect the concentrations of glucose, NEFA, insulin or glucagon in the fed state

Point-charge electrostatics in disordered alloys

A simple analytic model of point-ion electrostatics has been previously proposed in which the magnitude of the net charge q_i on each atom in an ordered or random alloy depends linearly on the number N_i^(1) of unlike neighbors in its first coordination shell. Point charges extracted from recent large supercell (256-432 atom) local density approximation (LDA) calculations of Cu-Zn random alloys now enable an assessment of the physical validity and accuracy of the simple model. We find that this model accurately describes (i) the trends in q_i vs. N_i^(1), particularly for fcc alloys, (ii) the magnitudes of total electrostatic energies in random alloys, (iii) the relationships between constant-occupation-averaged charges and Coulomb shifts (i.e., the average over all sites occupied by either $A$ or $B$ atoms) in the random alloy, and (iv) the linear relation between the site charge q_i and the constant- charge-averaged Coulomb shift (i.e., the average over all sites with the same charge) for fcc alloys. However, for bcc alloys the fluctuations predicted by the model in the q_i vs. V_i relation exceed those found in the LDA supercell calculations. We find that (a) the fluctuations present in the model have a vanishing contribution to the electrostatic energy. (b) Generalizing the model to include a dependence of the charge on the atoms in the first three (two) shells in bcc (fcc) - rather than the first shell only - removes the fluctuations, in complete agreement with the LDA data. We also demonstrate an efficient way to extract charge transfer parameters of the generalized model from LDA calculations on small unit cells.Comment: 15 pages, ReVTeX galley format, 7 eps figures embedded using psfig, to be published in Phys. Rev.

A fingerprint based metric for measuring similarities of crystalline structures

Measuring similarities/dissimilarities between atomic structures is important for the exploration of potential energy landscapes. However, the cell vectors together with the coordinates of the atoms, which are generally used to describe periodic systems, are quantities not suitable as fingerprints to distinguish structures. Based on a characterization of the local environment of all atoms in a cell we introduce crystal fingerprints that can be calculated easily and allow to define configurational distances between crystalline structures that satisfy the mathematical properties of a metric. This distance between two configurations is a measure of their similarity/dissimilarity and it allows in particular to distinguish structures. The new method is an useful tool within various energy landscape exploration schemes, such as minima hopping, random search, swarm intelligence algorithms and high-throughput screenings