Application of discriminant function analysis and change-point problem in dating volcanic ashes

The application of Discriminant function analysis (DFA) is not a new idea in the study of tephrochrology. In this paper, DFA is applied to compositional datasets of two different types of tephras from Mountain Ruapehu in New Zealand and Mountain Rainier in USA. The canonical variables from the analysis are further investigated with a statistical methodology of change-point problems in order to gain a better understanding of the change in compositional pattern over time. Finally, a special case of segmented regression has been proposed to model both the time of change and the change in pattern. This model can be used to estimate the age for the unknown tephras using Bayesian statistical calibration

An alternative method for dating unknown tephras based on a segmented regression model

In CoDaWork’05, we presented an application of discriminant function analysis (DFA) to 4 different compositional datasets and modelled the first canonical variable using a segmented regression model solely based on an observation about the scatter plots. In this paper, multiple linear regressions are applied to different datasets to confirm the validity of our proposed model. In addition to dating the unknown tephras by calibration as discussed previously, another method of mapping the unknown tephras into samples of the reference set or missing samples in between consecutive reference samples is proposed. The application of these methodologies is demonstrated with both simulated and real datasets. This new proposed methodology provides an alternative, more acceptable approach for geologists as their focus is on mapping the unknown tephra with relevant eruptive events rather than estimating the age of unknown tephra. Kew words: Tephrochronology; Segmented regression

Tolerance towards dating violence in Spanish adolescents

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Physical and psychological aggression in dating relationships in Spanish university students. 'Agresi??n f??sica y psicol??gica en las relaciones de noviazgo en universitarios espa??oles'

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Prevalence and predictors of sexual aggression in dating relationships of adolescents and young adults

Prevalencia y predictores de la agresi??n sexual en las relaciones de noviazgo en adolescentes y j??venes. Son muchos los estudios publicados que analizan las influencias di??dicas en las relaciones de noviazgo en adolescentes y j??venes adultos. El objetivo de este estudio consiste en aplicar el modelo di??dico de la agresi??n f??sica hacia las parejas a la agresi??n sexual contra las parejas. Se ha utilizado una muestra de 4.052 adolescentes y j??venes adultos de ambos sexos, con edades comprendidas entre los 16 y los 26 a??os. El porcentaje de hombres agresores es significativamente superior que el de mujeres (35,7 por ciento vs 14,9 por ciento), y el porcentaje de v??ctimas de agresi??n sexual fue superior para las mujeres (25,1 por ciento vs 21,7 por ciento). Los resultados muestran que tanto la agresi??n como la victimizaci??n sexual son fundamentalmente de naturaleza psicol??gica, como, por ejemplo, la utilizaci??n de t??cticas coercitivas de naturaleza verbal. Tal como predice el modelo di??dico de agresi??n f??sica en las relaciones de noviazgo, la victimizaci??n sexual se predice en funci??n de la agresi??n sexual de los individuos estudiados tanto en el caso de los hombres como en el de las mujeres.

Prevalence, risk factors, and problems associated with dating violence: A literature review

The physical, psychological and sexual violence among the couples of adolescents and young adults that are not married neither cohabiting (well-known generally as “dating violence”), has been object of a vast number of investigations in the last two decades that show a high prevalence inside the adolescent and juvenile population. The objective of this work was to carry out an analysis of the literature in connection with the prevalence, risk factors and difficulties associated with this partner violence type. This analysis allowed to elaborate an outline of the factors that could favor the acts of violence, including the previous experiences of victimization inside and outside the family, the acceptance of the violence toward the couple, and the relationship with pairs that have exercised this form of violence.

The importance of adolescent dating relationships

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Justification beliefs of violence, myths about love and cyber dating abuse

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Sexting, psychological distress and dating violence among adolescents and young adults

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Naturally occurring radioactive material (NORM) from a former phosphoric acid processing plant

In recent years there has been an increasing awareness of the radiological impact of non-nuclear industries that extract and/or process ores and minerals containing naturally occurring radioactive material (NORM). These industrial activities may result in significant radioactive contamination of (by-) products, wastes and plant installations. In this study, scale samples were collected from a decommissioned phosphoric acid processing plant. To determine the nature and concentration of NORM retained in pipe-work and associated process plant, four main areas of the site were investigated: (1) the 'Green Acid Plant', where crude acid was concentrated; (2) the green acid storage tanks; (3) the Purified White Acid (PWA) plant, where inorganic impurities were removed; and (4) the solid waste, disposed of on-site as landfill. The scale samples predominantly comprise the following: fluorides (e.g. ralstonite); calcium sulphate (e.g. gypsum); and an assemblage of mixed fluorides and phosphates (e.g. iron fluoride hydrate, calcium phosphate), respectively. The radioactive inventory is dominated by U-238 and its decay chain products, and significant fractionation along the series occurs. Compared to the feedstock ore, elevated concentrations (<= 8.8 Bq/g) of U-238 Were found to be retained in installations where the process stream was rich in fluorides and phosphates. In addition, enriched levels (<= 11 Bq/g) of Ra-226 were found in association with precipitates of calcium sulphate. Water extraction tests indicate that many of the scales and waste contain significantly soluble materials and readily release radioactivity into solution. (c) 2005 Elsevier Ltd. All rights reserved.

Dating the onset of cereal cultivation in Britain and Ireland: the evidence from charred cereal grains

When does Neolithic life begin in Britain? The author gathered up the current evidence for radiocarbon-dated first use of cereals, distinguishing between dates from charcoal in contexts with cereals, and dates from the charred grains themselves. The charred grains begin to appear around 4000 cal BC and become prominent in settlements between 3800 and 3000 cal BC This correlates well with the appearance of megalithic tombs (3800-3500 cal BC) and argues for a relatively rapid adoption of the Neolithic package during an experimental phase of two centuries, 4000-3800 cal BC. The early cereals reported in the pollen record (from 5000 BC) are attributed to wild species.

U-series isochron dating of immature and mature calcretes as a basis for constructing Quaternary landform chronologies for the Sorbas basin, southeast Spain

Immature and mature calcretes from an alluvial terrace sequence in the Sorbas basin, southeast Spain, were dated by the U-series isochron technique. The immature horizons consistently produced statistically reliable ages of high precision. The mature horizons typically produced statistically unreliable ages but, because of linear trends in the dataset and low errors associated with each data point, it was still possible to place a best-fit isochron through the dataset to produce an age with low associated uncertainties. It is, however, only possible to prove that these statistically unreliable ages have geochronological significance if multiple isochron ages are produced for a single site, and if these multiple ages are stratigraphically consistent. The geochronological significance of such ages can be further proven if at least one of the multiple ages is statistically reliable. By using this technique to date calcretes that have formed during terrace aggradation and at the terrace surface after terrace abandonment it is possible not only to date the timing of terrace aggradation but also to constrain the age at which the river switched from aggradation to incision. This approach, therefore, constrains the timing of changes in fluvial processes more reliably than any currently used geochronological procedure and is appropriate for dating terrace sequences in dryland regions worldwide, wherever calcrete horizons are present. (c) 2005 University of Washington. All rights reserved.