Theoretical Justification for Bond Valence -- Bond Length Empirical Correlations

Bond valence – bond length empirical correlations are of great interest in chemistry, biology, geology and materials science because they offer a quick and convenient way of checking and evaluating molecular structures. Linus Pauling’s relationship is the most commonly used, but is a two-parameter fit where R0 and b must be optimized. In this study, a simplified quantum-mechanical approach was used to derive Pauling’s empirical bond valence – bond length relationship. A covalency factor was also introduced to account for the difference in “softness” between cation and anion (resulting in increased orbital overlap). An expression for the b parameter was determined that yields values that are in agreement with experimental data. The derived relationship for the b parameter allows an independent determination of b using orbital exponents and electronegativity values for the cation and anion

Titanium-Oxygen Bond Length -Bond Valence Relationship

A bond length–bond valence correlation is a simple method of checking and evaluating molecular structures and is of great interest in chemistry, biology, geology, and material science. Recently, we used quantum-mechanical arguments to derive Pauling’s bond length-valence relationship and to define the adjustable fitting parameter b in terms of atomic-orbital exponents. Improved orbital exponents were generated for elements 1-103 using published atomic radii and single-bond covalent radii as well as a continuous function for effective principal quantum number. In this study, we use orbital exponents for titanium (Ti) and oxygen (O) to generate a bond length-valence relationship for Ti-O bonds. Recent crystallographic Ti-O bond lengths from 32 environments were collected and converted to Ti-O bond valences to check the reliability of the bond length-valence relationship where Ro was found (bond length of unit valence). This relationship is expected to apply to any Ti-O bond regardless of environment, physical state, or oxidation number

Multiproxy paleodietary reconstruction using stable isotopes and starch analysis: the case of the archaeological site of Playa del Mango, Granma, Cuba

Paleoethnobotanical and stable isotope studies have demonstrated that the indigenous groups that populated the Antilles, traditionally understood as dependent exclusively on wild resources, cultivated and consumed both C3 and C4 plants even before the arrival of the ceramic-bearing Arawak groups. However, the relative importance of cultigens and the differential use of plants, especially maize, between populations and individuals remains un-known. In this paper we combined the analysis of stable isotopes (delta 15N, delta 13Cco, delta 13Cen, delta 13Cap, delta 34S) of 27 in-dividuals from the archaeological site of Playa del Mango, Cuba with the identification of starch grains in dental calculus. The stable isotope results indicate that the sampled population had a 70:30 C3/C4 diet, where at least 65 % was based on C3 protein. Starches from C3 (e.g., Marantaceae, Ipomoea batatas) and C4 plants (Zea mays) were found in similar proportions (50:50). These results support that the lack or abundance of starch grains cannot be used to infer directly the frequency at which C3 and C4 plants were consumed within a small popu-lation. Statistically significant differences between females and males in the carbon isotope composition of diet, and its energy portion, suggests a differential consumption of plants by sex. Playa del Mango individual diets were statistically different from those of coeval sites, supporting our previous findings that groups with different dietary traditions concurrently inhabited Cuba in precolonial times. The study demonstrates the power of combined use of stable isotope models, and starch analysis, to provide a more nuanced reconstruction of dietary practices in past human populations.Archaeological science

The population genomic legacy of the second plague pandemic

SummaryHuman populations have been shaped by catastrophes that may have left long-lasting signatures in their genomes. One notable example is the second plague pandemic that entered Europe in ca. 1,347 CE and repeatedly returned for over 300 years, with typical village and town mortality estimated at 10%–40%.1 It is assumed that this high mortality affected the gene pools of these populations. First, local population crashes reduced genetic diversity. Second, a change in frequency is expected for sequence variants that may have affected survival or susceptibility to the etiologic agent (Yersinia pestis).2 Third, mass mortality might alter the local gene pools through its impact on subsequent migration patterns. We explored these factors using the Norwegian city of Trondheim as a model, by sequencing 54 genomes spanning three time periods: (1) prior to the plague striking Trondheim in 1,349 CE, (2) the 17th–19th century, and (3) the present. We find that the pandemic period shaped the gene pool by reducing long distance immigration, in particular from the British Isles, and inducing a bottleneck that reduced genetic diversity. Although we also observe an excess of large FST values at multiple loci in the genome, these are shaped by reference biases introduced by mapping our relatively low genome coverage degraded DNA to the reference genome. This implies that attempts to detect selection using ancient DNA (aDNA) datasets that vary by read length and depth of sequencing coverage may be particularly challenging until methods have been developed to account for the impact of differential reference bias on test statistics.Results and discussion STAR★Method

The population genomic legacy of the second plague pandemic

Human populations have been shaped by catastrophes that may have left long-lasting signatures in their genomes. One notable example is the second plague pandemic that entered Europe in ca. 1,347 CE and repeatedly returned for over 300 years, with typical village and town mortality estimated at 10%-40%.1 It is assumed that this high mortality affected the gene pools of these populations. First, local population crashes reduced genetic diversity. Second, a change in frequency is expected for sequence variants that may have affected survival or susceptibility to the etiologic agent (Yersinia pestis).2 Third, mass mortality might alter the local gene pools through its impact on subsequent migration patterns. We explored these factors using the Norwegian city of Trondheim as a model, by sequencing 54 genomes spanning three time periods: (1) prior to the plague striking Trondheim in 1,349 CE, (2) the 17th-19th century, and (3) the present. We find that the pandemic period shaped the gene pool by reducing long distance immigration, in particular from the British Isles, and inducing a bottleneck that reduced genetic diversity. Although we also observe an excess of large FST values at multiple loci in the genome, these are shaped by reference biases introduced by mapping our relatively low genome coverage degraded DNA to the reference genome. This implies that attempts to detect selection using ancient DNA (aDNA) datasets that vary by read length and depth of sequencing coverage may be particularly challenging until methods have been developed to account for the impact of differential reference bias on test statistics

Assessing human diet and movement in the Tongan maritime chiefdom using isotopic analyses.

The rise of stratified societies fundamentally influences the interactions between status, movement, and food. Using isotopic analyses, we assess differences in diet and mobility of individuals excavated from two burial mounds located at the `Atele burial site on Tongatapu, the main island of the Kingdom of Tonga (c. 500 - 150 BP). The first burial mound (To-At-1) was classified by some archaeologists as a commoner's mound while the second burial mound (To-At-2) was possibly used for interment of the chiefly class. In this study, stable isotope analyses of diet (δ13C, δ15N, and δ34S; n = 41) are used to asses paleodiet and 87Sr/86Sr ratios (n = 30) are analyzed to investigate individual mobility to test whether sex and social status affected these aspects of life. Our results show significant differences in diet between burial mounds and sexes. Those interred in To-At-2 displayed lower δ13C values, indicating they ate relatively more terrestrial plants (likely starchy vegetable staples) compared with To-At-1 individuals. Females displayed significantly lower δ15N values compared with males within the entire assemblage. No differences in δ34S values were observed between sexes or burial mound but it is possible that sea spray or volcanism may have affected these values. One individual displayed the strontium isotopic composition representative of a nonlocal immigrant (outside 2SD of the mean). This suggests the hegemonic control over interisland travel, may have prevented long-term access to the island by non-Tongans exemplifying the political and spiritual importance of the island of Tongatapu in the maritime chiefdom

Disease: A Hitherto Unexplored Constraint on the Spread of Dogs (Canis lupus familiaris) in Pre-Columbian South America

Although debate continues, there is agreement that dogs (Canis lupus familiaris) were first domesticated in Eurasia, spreading from there to other parts of the world. However, while that expansion already extended as far as Europe, China, and North America by the early Holocene, dogs spread into (and south of) the tropics only much later. In South America, for example, the earliest well attested instances of their presence do not reach back much beyond 3000 cal. BC, and dogs were still absent from large parts of the continent – Amazonia, the Gran Chaco, and much of the Southern Cone – at European contact. Previous explanations for these patterns have focused on cultural choice, the unsuitability of dogs for hunting certain kinds of tropical forest prey, and otherwise unspecified environmental hazards, while acknowledging that Neotropical lowland forests witness high rates of canine mortality. Building on previous work in Sub-Saharan Africa (Mitchell 2015) and noting that the dog’s closest relatives, the grey wolf (C. lupus) and the coyote (C. latrans), were likewise absent from South and most of Central America in Pre- Columbian times, this paper explores instead the possibility that infectious disease constrained the spread of dogs into Neotropical environments. Four diseases are considered, all likely to be native and/or endemic to South America: canine distemper, canine trypanosomiasis, canine rangeliosis, and canine visceral leishmaniasis caused by infection with Leishmania amazonensis and L. colombiensis. The paper concludes by suggesting ways in which the hypothesis that disease constrained the expansion of dogs into South America can be developed further

Benchmarking Trisaminocyclopropeniums as Mediators for Anodic Oxidation Reactions

This report benchmarks a tris(amino)cyclopropenium (TAC) salt as an electron-transfer mediator for anodic oxidation reactions in comparison to two known mediators: a triarylamine and a triarylimidazole derivative. The three mediators have redox potentials, diffusion coefficients, and heterogeneous electron transfer rates similar to those of glassy carbon electrodes in acetonitrile/KPF6. However, they differ significantly in their performance in two electro-organic reactions: anodic fluorination of a dithiane and anodic oxidation of 4-methoxybenzyl alcohol. These differences are rationalized based on variable stability in the presence of reaction components (e.g., NEt3·3HF, lutidine, and Cs2CO3) as well as very different rates of electron transfer with the organic substrate. Overall, this work highlights the advantages and disadvantages of each mediator and provides a foundation for expanding the applications of TACs in electro-organic synthesis moving forward

Precolonial/early colonial human burials from the site of White Marl, Jamaica: New findings from recent rescue excavations

Archaeology of the America

A Multi-Isotope Investigation of Human and Dog Mobility and Diet in the Pre-Colonial Antilles

The complex relationships between humans and dogs (Canis lupus familiaris) have a very deep and unique history. Dogs have accompanied humans as they colonised much of the world, and were introduced via human agency into the insular Caribbean where they became widespread throughout the Ceramic Age. It is likely that the dynamic interactions between humans, dogs, and their environments in the Caribbean were spatially, chronologically, and socially variable. However, almost no research has specifically addressed the nature, or potential variability, of human/dog interactions in this region. This study presents isotopic (strontium and carbon) evidence bearing on human and dog paleomobility and paleodietary patterns in the pre-colonial Caribbean. The isotope results illustrate a generally high degree of correspondence between human and dog dietary practices at all analysed sites but also slight differences in the relative importance of different dietary inputs. Striking parallels are also observed between the human and dog mobility patterns and shed light on broader networks of social interaction and exchange. Lastly, the paper addresses the possible utility and relevance of canine isotope data as proxies for inferring past human behaviours.Seventh Framework Programme (FP7)Archaeology of the America