JAAS News

This paper presents a new analytical technique for the high-precision measurement of ²²⁸Ra/²²⁶Ra ratios and Ra concentrations in seawater by multi-collector ICP mass spectrometry (MC-ICP-MS). Yu-Te Hsieh and Gideon M. Henderson from the University of Oxford, UK, demonstrate that the technique, relative to commonly used decay-counting approaches, has a lower detection limit and higher precision.  This technique will allow study of ²²⁸Ra in the ocean interior where concentrations are low and will extend the powerful use of this isotope to understand mixing and trace element fluxes in the oceans.

Interested in knowing more?  Read the full article here; free until 8th April!

Precise measurement of ²²⁸Ra/²²⁶Ra ratios and Ra concentrations in seawater samples by multi-collector ICP mass spectrometry
Yu-Te Hsieh and Gideon M. Henderson
J. Anal. At. Spectrom., 2011, Advance Article
DOI: 10.1039/C1JA10013K

A microwave discharge using <1 W is demonstrated as a spectroscopic source for detection of sulfur, hydrocarbons, and oxygen.

Atmospheric pressure microplasmas are a promising technology for low-power optical emission spectroscopy for chemical detection. In this work, Alan Hoskinson and co-workers from Massachusetts, USA examine a microstrip split-ring resonator (MSRR) discharge operating at 1.8 GHz in helium as an excitation source. The source can sustain a plasma with as little as 0.2 W of microwave power, and can be operated continuously with no electrode damage.

Based on the stability, low power consumption and detection limits, which compare favourably to other low and moderate power plasma excitation sources, the MSRR plasma is a promising technology for use in portable systems.

Interested in knowing more? Read for free until 4^th April.

Low-power microwave-generated helium microplasma for molecular and atomic spectrometry
Alan R. Hoskinson, Jeffrey Hopwood, Neil W. Bostrom, Jeffrey A. Crank and Christopher Harrison
J. Anal. At. Spectrom., 2011, Advance Article
DOI: 10.1039/C0JA00239A

Tools used in the chasing process

This study by R. van Langh and co-workers adds analytical data to the debate on whether bronze sculptures could have been cast with such a precision that no after-work was required.  The study focuses on chasing, a technique based on flattening the surface using a hammer and iron chasing tool; it is applied on each bronze after it has been cast and is removed from the mould.

Bastiano Torrigiani's sculpture: Bust of Pope Gregory XIV

In the past these bronzes have always been considered as cast and chased, but during a careful study of Renaissance bronzes in the collection of the Rijksmuseum, two bronzes clearly distinguished themselves. On both Hercules Pomarius by Willem van Tetrode and Bastiano Torrigiani’s sculpture Bust of Pope Gregory XIV, flashes of metal were found on the outer surface of the bronze leading to the hypothesis that a bronze statuette could have been cast in the 16^th century with such precision that no chasing of the surface had to take place. The aim of this research was to point out the characteristic “strain fingerprints” left in the bronze by the chasing process, which are absent in an “as cast” specimen: the use of Time of Flight Neutron Diffraction for this purpose is a novel application.

Severo Calzetta da Ravenna's bronze statuette depicting Paris in the the diffractometer ENGIN-X

The team compared Hercules Pomarius and Bust of Pope Gregory XIV with the undoubtedly cast and chased Severo Calzetta da Ravenna’s bronze statuette depicting Paris, as well as two specifically manufactured reference samples, one cast and chased, the other cast and unfinished.  They demonstrated that both the Bust of Pope Gregory XIV and Hercules Pomarius were cast and not chased and Paris was cast and chased.

This article will be published later in the year as part of a themed issue on Art & Archaeometry.

Interested in knowing more? Read the article for free until March 1st!

Casting technology of Renaissance bronze statuettes: the use of TOF-neutron diffraction for studying afterwork of Renaissance casting techniques
R. van Langh, L. Bartoli, J. Santisteban and D. Visser
J. Anal. At. Spectrom., 2011, Advance Article
DOI: 10.1039/C0JA00235F