scholarly journals Testing the Effectiveness of Protocols for Removal of Common Conservation Treatments for Radiocarbon Dating

Radiocarbon ◽  
2017 ◽  
Vol 60 (1) ◽  
pp. 35-50 ◽  
Author(s):  
Fiona Brock ◽  
Michael Dee ◽  
Andrew Hughes ◽  
Christophe Snoeck ◽  
Richard Staff ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Vinyl Acetate ◽  
Radiocarbon Dating ◽  
Cellulose Nitrate ◽  
Acid Base ◽  
Acrylic Polymers ◽  
Archaeological Wood ◽  
Conservation Treatment ◽  
Chemical Pretreatments ◽  
Selection Of

AbstractTo achieve a reliable radiocarbon (14C) date for an object, any contamination that may be of a different age must be removed prior to dating. Samples that have been conserved with treatments such as adhesives, varnishes or consolidants can pose a particular challenge to 14C dating. At the Oxford Radiocarbon Accelerator Unit (ORAU), common examples of such substances encountered include shellac, the acrylic polymers Paraloid B-67 and B-72, and vinyl acetate-derived polymers (e.g. PVA). Here, a non-carbon-containing absorbent substrate called Chromosorb® was deliberately contaminated with a range of varieties or brands of these conservation treatments, as well as two cellulose nitrate lacquers. A selection of chemical pretreatments was tested for their efficiency at removing them. While the varieties of shellac and Paraloid tested were completely removed with some treatments (water/methanol and acetone/methanol/chloroform sequential washes, respectively), no method was found that was capable of completely removing any of the vinyl acetate-derived materials or the cellulose nitrate lacquers. While Chromosorb is not an exact analog of archaeological wood or bone, for example, this study suggests that it may be possible to remove aged shellac and Paraloid from archaeological specimens with standard organic solvent-acid-base-acid pretreatments, but it may be significantly more difficult to remove vinyl acetate-derived polymers and cellulose nitrate lacquers sufficiently to provide reliable 14C dates. The four categories of conservation treatment studied demonstrate characteristic FTIR spectra, while highlighting subtle chemical and molecular differences between different varieties of shellac, Paraloid and cellulose nitrate lacquers, and significant differences between the vinyl acetate derivatives.

SUITABILITY OF ACID-SOLUBLE AND ACID-INSOLUBLE LEATHER FRACTIONS IN RADIOCARBON DATING

Radiocarbon ◽  
2020 ◽  
pp. 1-8
Author(s):  
Alyssa M Tate ◽  
Brittany Hundman ◽  
Jonathan Heile
Keyword(s):  
Radiocarbon Dating ◽  
Insoluble Fraction ◽  
Economic Life ◽  
Chemical Pretreatment ◽  
Acid Base ◽  
The Past ◽  
Acid Soluble Collagen ◽  
Method Of Production ◽  
Insight Into

ABSTRACT Leather has been produced by a variety of methods throughout human history, providing researchers unique insight into multiple facets of social and economic life in the past. Archaeologically recovered leather is often fragile and poorly preserved, leading to the use of various conservation and restoration efforts that may include the application of fats, oils, or waxes. Such additives introduce exogenous carbon to the leather, contaminating the specimen. These contaminants, in addition to those accumulated during interment, must be removed through chemical pretreatment prior to radiocarbon (14C) dating to ensure accurate dating. DirectAMS utilizes organic solvents, acid-base-acid (ABA) and gelatinization for all leather samples. Collagen yield from leather samples is variable due to the method of production and the quality of preservation. However, evaluating the acid-soluble collagen fraction, when available, provides the most accurate 14C dates for leather samples. In instances where gelatinization does not yield sufficient material, the resulting acid-insoluble fraction may be dated. Here we examine the effectiveness of the combined organic solvent and ABA pretreatment with gelatinization for leather samples, as well as the suitability of the acid-insoluble fraction for 14C dating.

Changes in metabolic rate and N excretion in the marine invertebrateSipunculus nudusunder conditions of environmental hypercapnia

2002 ◽  
Vol 205 (8) ◽  
pp. 1153-1160 ◽  
Author(s):  
M. Langenbuch ◽  
H. O. Pörtner
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Metabolic Rate ◽  
Intracellular Ph ◽  
Energy Demand ◽  
Control Level ◽  
Ammonia Excretion ◽  
Amino Acid Catabolism ◽  
Acid Base ◽  
Selection Of

SUMMARYIncreased CO2 partial pressures (hypercapnia) as well as hypoxia are natural features of marine environments like the intertidal zone. Nevertheless little is known about the specific effects of CO2 on metabolism, except for the well-described effects on acid—base variables and regulation. Accordingly, the sediment-dwelling worm Sipunculus nudus was used as an experimental model to investigate the correlation of acid—base-induced metabolic depression and protein/amino acid catabolism, by determining the rates of oxygen consumption, ammonia excretion and O/N ratios in non-perfused preparations of body wall musculature at various levels of extra- and intracellular pH, PCO2 and [HCO3-]. A decrease in extracellular pH from control level (7.9) to 6.7 caused a reduction in aerobic metabolic rate of both normocapnic and hypercapnic tissues by 40-45 %. O/N ratios of 4.0-4.5 under control conditions indicate that amino acid catabolism meets the largest fraction of aerobic energy demand. A significant 10-15 % drop in ammonia excretion, a simultaneous reduction of O/N ratios and a transient accumulation of intracellular bicarbonate during transition to extreme acidosis suggest a reduction in net amino acid catabolism and a shift in the selection of amino acids used,favouring monoamino dicarboxylic acids and their amines (asparagine,glutamine, aspartic and glutamic acids). A drop in intracellular pH was identified as mediating this effect. In conclusion, the present data provide evidence for a regulatory role of intracellular pH in the selection of amino acids used by catabolism.

BIOCATALYTIC PROCESSES OF LOW-TEMPERATURE SYNTHESIS OF ESTERS. MODULATION OF THE FUNCTIONAL PROPERTIES OF LIPASE BY THE CHOICE OF SOLVENT AND SUPPORT FOR IMMOBILIZATION

2021 ◽  
Vol 1 (19) ◽  
pp. 271-273
Author(s):  
L.V. Perminova ◽  
M.B. Pykhtina ◽  
A.B. Beklemishev
Keyword(s):  
Organic Solvent ◽  
Functional Properties ◽  
Chemical Nature ◽  
Immobilized Lipase ◽  
Carbon Aerogel ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Heterogeneous Biocatalysts ◽  
Adsorptive Immobilization ◽  
Selection Of

Biocatalytic processes for the synthesis of valuable products, such as different esters for various purposes, have been studied using heterogeneous biocatalysts prepared by immobilizing the recombinant lipase rPichia/lip on mesoporous silica (SiO2) and macroporous carbon aerogel (MCA). It was found that the functional properties of immobilized lipase, such as enzymatic activity, specificity toward pair of substrates (acid and alcohol), the molecules of which differ in the number of carbon atoms (C), as well as operational stability, depended on the method of adsorptive immobilization, the chemical nature of the support, and polarity of the organic solvent, i.e. logP. The functional properties of rPichia/lip have been shown to be modulated by the selection of an organic solvent and support for lipase immobilization.

scholarly journals Radiocarbon Dating of Pleistocene Bone: Toward Criteria for the Selection of Samples

Radiocarbon ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 969-979 ◽  
Author(s):  
R E Taylor
Keyword(s):  
Amino Acid ◽  
Stable Isotope ◽  
Amino Acid Composition ◽  
Radiocarbon Dating ◽  
Detection System ◽  
High Energy ◽  
Mass Spectrometric ◽  
Stable Isotope Ratios ◽  
Sources Of Information ◽  
Selection Of

Amino acid composition data and stable isotope ratios (14N, D, and13C) are being evaluated as sources of information to indicate the presence of non-indigenous organics in bone samples intended for 14C analyses. The study is being conducted in the context of the planned measurement of Pleistocene bone samples by a high energy mass spectrometric 14C detection system.

scholarly journals Kinetic Studies on Lipase-Catalyzed Acetylation of 2-Alkanol with Vinyl Acetate in Organic Solvent

2007 ◽  
Vol 56 (6) ◽  
pp. 309-317 ◽  
Author(s):  
Hirofumi Hirata ◽  
Mio Kawanishi ◽  
Yusuke Iwata ◽  
Keiji Sakaki ◽  
Hiroshi Yanagishita
Keyword(s):  
Organic Solvent ◽  
Vinyl Acetate ◽  
Kinetic Studies

scholarly journals 14C Dating Compared to Art Historical Dating of Roman and Coptic Textiles from Egypt

Radiocarbon ◽  
2004 ◽  
Vol 46 (1) ◽  
pp. 231-244 ◽  
Author(s):  
Mark Van Strydonck ◽  
Antoine De Moor ◽  
Dominique Bénazeth
Keyword(s):  
Radiocarbon Dating ◽  
Interquartile Range ◽  
14C Dating ◽  
Art Historians ◽  
Representative Selection ◽  
The Individual ◽  
Selection Of ◽  
Individual Objects

A representative selection of Roman and Coptic textiles is used to compare the radiocarbon dating results with the chronology proposed by art historians. In some cases, the comparison was made on individual objects, but in other cases, groups of stylistically and/or technologically related textiles were compared. In the case of the latter, the interquartile range was calculated. The results of this comparison show that some individual samples and groups are dated older than expected, while for another group the opposite is the case. One group was matching well with the presumed period as a whole, but not on the basis of the individual pieces. The analyses showed the necessity of 14C dating to obtain a more accurate dating of Coptic textiles.

scholarly journals Identification, Extraction, and Preparation of Reliable Lime Samples for 14C Dating of Plasters and Mortars with the “Pure Lime Lumps” Technique

Radiocarbon ◽  
2012 ◽  
Vol 54 (3-4) ◽  
pp. 933-942 ◽  
Author(s):  
Giovanni L A Pesce ◽  
Richard J Ball ◽  
Gianluca Quarta ◽  
Lucio Calcagnile
Keyword(s):  
Case Studies ◽  
Radiocarbon Dating ◽  
Historic Sites ◽  
14C Dating ◽  
Relative Simplicity ◽  
Lime Mortars ◽  
The Matrix ◽  
The 1960S ◽  
Selection Of ◽  
Contamination Problem

Radiocarbon dating was first applied to historic lime mortars during the 1960s. However, despite the relative simplicity of the technique in principle, a number of subsequent studies have highlighted important aspects that should be considered. One of the most significant of these challenges arises from sample contamination by carbonaceous substances such as incompletely burnt limestone and aggregates of fossil origin containing “dead” 14C. More recent studies have shown that in the majority of old lime-based mixtures the contamination problem can be avoided through selection of pure lime lumps. These particular types of lumps are believed to originate from areas where the lime is incompletely mixed with the aggregate. It has been demonstrated that even a single lime lump can provide sufficient material for a 14C date of the mortar from which the lump was taken (Pesce et al. 2009). This paper describes the practical challenges associated with location, extraction, and preparation of 4 lime lumps extracted from 2 new sites for 14C dating. These include distinguishing the lime lumps from other lumps present in the matrix and the removal of material surrounding the lime lump. The coherence of 14C dating with other archaeological information on the chronology of historic sites is highlighted through case studies.

Sign in / Sign up

Export Citation Format

Share Document