The fission yield of 99Tc from 239Pu and 235U is similar to that of 137Cs or 90Sr and it is therefore an important component of nuclear weapons fall-out, nuclear waste and releases from nuclear facilities. There is particular current interest in 99Tc transfer from soil to plants for: (a) environmental impact assessments for terrestrial nuclear waste repositories, and (b) assessments of the potential for phytoextraction of radionuclides from contaminated effluent and soil. Vascular plants have a high 99Tc uptake capacity, a strong tendency to transport it to shoot material and accumulate it in vegetative rather than reproductive structures. The mechanisms that control 99Tc entry to plants have not been identified and there has been little discussion of the potential for phytoextraction of 99Tc contaminated effluents or soil. Here we review soil availability, plant uptake mechanisms and soil to plant transfer of 99Tc in the light of recent advances in soil science, plant molecular biology and phytoextraction technologies. We conclude that 99Tc might not be highly available in the long term from up to 50% of soils worldwide, and that no single mechanism that might be easily targeted by recombinant DNA technologies controls 99Tc uptake by plants. Overall, we suggest that Tc might be less available in terrestrial ecosystems than is often assumed but that nevertheless the potential of phytoextraction as a decontamination strategy is probably greater for 99Tc than for any other nuclide of radioecological interest.

The paper reviews some of the important recent developments within the MERCI project in the technical improvement and deployment of Multimedia conferencing. The developments address four of the known limitations of the Mbone technology heretofore: lack of security, absence of QoS guarantees, inability to interwork with conferences using the ITU-T standards and lack of good access over low bandwidth unicast links. Description of the developments is coupled with a discussion of future improvements and plans for further deployment.

Use of the Internet for multimedia conferencing began in the early 1990s. Multimedia conferencing allows people at multiple, distributed locations to communicate using audio, video and shared workspace programs; the Multicast Backbone of the Internet (MBONE) provides the technical solution to make the most efficient use of the limited Internet bandwidth for such interactions. The scope for using this technology in medical applications was recognised by the MICE project which, in November 1994, used Sun SPARC workstations connected to the MBONE to send video and commentary of live operations from Sweden and San Francisco to a workshop held in London. These sessions were marred by severe congestion experienced on the networks on the day, but the consensus of those organising and attending the workshop was that the exercise was worthwhile. The main lessons learnt from this first transmission were the need to provide better quality links and to ensure confidentiality. In December 1995, the MERCI project, funded by the European Union under the TELEMATICS for Research programme, began work to refine and further propagate the use of the multimedia conferencing software. Part of this work is to provide these improved facilities to transmit operations to two more workshops scheduled for 1997. MERCI will offer confidentiality through encryption facilities built into the conferencing programs, improved programs which cope better with adverse network conditions, use of the new high-speed JAMES network and access to a multimedia server from which recordings of operations and medical instrumentation can be delivered to the workshop participants.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination of polyhalogenated hydrocarbons by glass capillary gas chromatography-negative ion chemical ionization mass spectrometryFrank W. Crow, Alf. Bjorseth, Kenneth T. Knapp, and Roy. BennettCite this: Anal. Chem. 1981, 53, 4, 619–625Publication Date (Print):April 1, 1981Publication History Published online1 May 2002Published inissue 1 April 1981https://pubs.acs.org/doi/10.1021/ac00227a014https://doi.org/10.1021/ac00227a014research-articleACS PublicationsRequest reuse permissionsArticle Views168Altmetric-Citations43LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts