From the Mendeleev periodic table to particle physics and back to the periodic table

We briefly describe in this paper the passage from Mendeleev's chemistry (1869) to atomic physics (in the 1900's), nuclear physics (in the 1932's) and particle physics (from 1953 to 2006). We show how the consideration of symmetries, largely used in physics since the end of the 1920's, gave rise to a new format of the periodic table in the 1970's. More specifically, this paper is concerned with the application of the group SO(4,2)xSU(2) to the periodic table of chemical elements. It is shown how the Madelung rule of the atomic shell model can be used for setting up a periodic table that can be further rationalized via the group SO(4,2)xSU(2) and some of its subgroups. Qualitative results are obtained from this nonstandard table.Comment: 15 pages; accepted for publication in Foundations of Chemistry (special issue to commemorate the one hundredth anniversary of the death of Mendeleev who died in 1907); version 2: 16 pages; some sentences added; acknowledgment and references added; misprints correcte

Archaeological sites and palaeoenvironments of Pleistocene West Africa

African paleoanthropological studies typically focus on regions of the continent such as Eastern, Southern and Northern Africa, which hold the highest density of Pleistocene archaeological sites. Nevertheless, lesser known areas such as West Africa also feature a high number of sites. Here, we present a high-resolution map synthesising all well contextualised Pleistocene archaeological sites present in Sub-Saharan West Africa. A detailed elevation and ecoregional map was developed and correlated with palaeoanthropological sites. This map is supplemented with 1,000- and 2000-year interval climate reconstructions over the last 120,000 years for three subregions of high archaeological interest. The presented archaeological sites were compiled by reviewing published literature, and selected based on: (1) documented archaeological stratification or >10 characteristic artefacts, (2) published coordinates, and (3) published chronometric ages or relative dating. The data presented here elucidates the current state of knowledge of Pleistocene West Africa, highlighting the regional potential for human evolutionary studies.1. Introduction 2. Data and methods 3. Map description 4. Discussio

Exploring Large Document Repositories with RDF Technology: The DOPE Project

This thesaurus-based search system uses automatic indexing, RDF-based querying, and concept-based visualization of results to support exploration of large online document repositories

A taxonomic and taphonomic study of Pleistocene fossil deposits from the western Nefud Desert, Saudi Arabia

Over the past decade, a growing interest has developed on the archaeology, palaeontology, and palaeoenvironments of the Arabian Peninsula. It is now clear that hominins repeatedly dispersed into Arabia, notably during pluvial interglacial periods when much of the peninsula was characterised by a semiarid grassland environment. During the intervening glacial phases, however, grasslands were replaced with arid and hyperarid deserts. These millennial-scale climatic fluctuations have subjected bones and fossils to a dramatic suite of environmental conditions, affecting their fossilisation and preservation. Yet, as relatively few palaeontological assemblages have been reported from the Pleistocene of Arabia, our understanding of the preservational pathways that skeletal elements can take in these types of environments is lacking. Here, we report the first widespread taxonomic and taphonomic assessment of Arabian fossil deposits. Novel fossil fauna are described and overall the fauna are consistent with a well-watered semiarid grassland environment. Likewise, the taphonomic results suggest that bones were deposited under more humid conditions than present in the region today. However, fossils often exhibit significant attrition, obscuring and fragmenting most finds. These are likely tied to wind abrasion, insolation, and salt weathering following fossilisation and exhumation, processes particularly prevalent in desert environments

Two cases of occupational allergic contact dermatitis from a cycloaliphatic epoxy resin in a neat oil: Case Report

BACKGROUND: Metal-working fluids contain complex mixtures of chemicals and metal workers constitute a potential risk group for the development of allergic contact dermatitis. CASE PRESENTATION: Two metal workers developed allergic contact dermatitis on the hands and lower arms from exposure to a neat oil used in metal processing. Patch testing revealed that the relevant contact allergen was a cycloaliphatic epoxy resin, 1,2-cyclohexanedicarboxylic acid, bis(oxiranylmethyl) ester, added to the oil as a stabilizer. None of the patients had positive reactions to the bisphenol A-based epoxy resin in the standard series. CONCLUSIONS: These cases emphasize that well-known contact allergens may show up from unexpected sources of exposure. Further, it can be a long-lasting, laborious process to detect an occupational contact allergen and cooperation from the patient and the manufacturer of the sensitizing product is essential