Manuscripts should be submitted as electronic attachments in postscript or pdf format (whenever possible) to Jane Spurr, ( jda@kcl.ac.uk ). The message should include the author(s) names and affiliations, the title of the paper and the name of the editor-in-chief who is best suited to deal with the submission.

Only original manuscripts are accepted for review, with the understanding that the same work has not been, will not be and is not presently submitted elsewhere, and that its submission for publication has been approved by all of the authors and by the institution where the work was carried out. If accepted, it will not be published elsewhere in the same form, in English or in any other language, without the written consent of the Publisher. Papers previously presented in conference proceedings of limited circulation maybe judged eligible for publication in revised form. The editor-in-chief to whom the paper is sent must be informed of such prior presentation at the time a manuscript is submitted.

Upon acceptance of an article, the author(s) will be asked to transfer copyright (for more information on copyright see http://elsevier.com/authors). This transfer will ensure the widest possible dissemination of information. A letter will be sent to the corresponding author confirming receipt of the manuscript. A form facilitating transfer of copyright will be provided. No page charge is made. Please note that typesetting costs of author's corrections in proof, other than the printer's errors, will be charged to the author.

If excerpts from other copyrighted works are included, the author(s) must obtain written permission from the copyright owners and credit the source(s) in the article. Elsevier has preprinted forms for use by authors in these cases: contact Elsevier Rights Department, phone: (+44) 1865 843830, fax: (+44) 1865 853333, email: permissions@elsevier.com. Requests may also be completed online via the Elsevier homepage ( http://www.elsevier.com/locate/permissions).

Should authors be requested by the Editor to revise the text, the revised version should be submitted within 12 weeks. After this period, the article will be regarded as a new submission.

LaTeX documents

The Elsevier LaTeX package (including detailed instructions for LaTeX preparation) can be obtained from the Elsevier website at http://elsevier.com/authors or from the Comprehensive TeX Archive Network (CTAN): see below. It consists of the files: elsart.cls (use this file if you are using LaTeX2e, the current version of LaTeX), elsart.sty and elsart12.sty (use these two files if you are using LaTeX2.09, the previous version of LaTeX), guidelines for users of elsart, a template file for quick start, and the instruction booklet "Preparing articles with LaTeX".

To obtain the package from CTAN, use direct access via FTP at ftp.dante.de (Germany), ftp.tex.ac.uk (UK), or ctan.tug.org (Massachusetts, USA) and go to the directory /tex-archive/macros/latex/contrib/supported/elsevier, or search for Elsevier with one of the CTAN search engines http://ctan.tug.org/CTANfind.html, http://www.tex.ac.uk/CTANfind.html or http://www.dante.de/cgi-bin/ctan-index. CTAN is a mirrored network of ftp.tex.ac.uk, ftp.dante.de and ctan.tug.org, which are widely mirrored (see ftp://ctan.tug.org/tex-archive/README.mirrors) and hold up-to-date copies of all the public-domain versions of TeX, LaTeX, Metafont and ancillary programs.

Figures may be inserted in the usual way using an \includegraphics command, at the position in the article where they are cited.

Your LaTeX file will be most useful as input for the printed article if you obey the following rules of thumb:

1. Be consistent. If you use a macro for a phrase, use it throughout.
2. Use standard LaTeX mark-up. Do not hardcode your own layout for e.g. section headings, but use the usual LaTeX macro for this purpose.
3. Keep it simple. Do not define macros that accomplish complicated layout. They will also make the input process complicated.
   
   

Presentation of manuscript

General

Please write your text in good English (American or British usage is accepted, but not a mixture of these). Italics are not to be used for expressions of Latin origin, for example, in vivo, et al., per se. Use decimal points (not commas); use a space for thousands (10 000 and above).

Authors in Japan kindly note that, upon request, Elsevier Japan will provide a list of people who can check and improve the English of an article before submission. Contact our Tokyo office: Elsevier K.K., Editorial Service, 4F Higashi-Azabu, 1 Chome Bldg, 1-9-15 Azabu, Minato-ku, Tokyo 106-0044, Japan; tel.: 03-5561-5037; fax: 03-5561-5047; e-mail: jp.info@elsevier.com.

Print the entire manuscript on one side of the paper only, using double spacing and wide (3 cm) margins. (Avoid full justification, i.e., do not use a constant right-hand margin.) Ensure that each new paragraph is clearly indicated. Present tables and figure legends on separate pages at the end of the manuscript. If possible, consult a recent issue of the journal to become familiar with layout and conventions. Number all pages consecutively.

Provide the following data on the title page (in the order given).

Title. Concise and informative. Titles are often used in information-retrieval systems. Avoid abbreviations and formulae where possible.

Author names and affiliations. Where the family name may be ambiguous (e.g., a double name), please indicate this clearly. Present the authors' affiliation addresses (where the actual work was done) below the names. Indicate all affiliations with a lower-case superscript letter immediately after the author's name and in front of the appropriate address. Provide the full postal address of each affiliation, including the country name, and, if available, the e-mail address of each author.

Corresponding author. Clearly indicate who is willing to handle correspondence at all stages of refereeing and publication, also post-publication. Ensure that telephone and fax numbers (with country and area code) are provided in addition to the e-mail address and the complete postal address.

Present/permanent address. If an author has moved since the work described in the article was done, or was visiting at the time, a 'Present address' (or 'Permanent address') may be indicated as a footnote to that author's name. The address at which the author actually did the work must be retained as the main, affiliation address. Superscript Arabic numerals are used for such footnotes.

Abstract. A concise and factual abstract is required. The abstract should state briefly the purpose of the research, the principal results and major conclusions. An abstract is often presented separate from the article, so it must be able to stand alone.

References should therefore be avoided, but if essential, they must be cited in full, without reference to the reference list.

Non-standard or uncommon abbreviations should be avoided, but if essential they must be defined at their first mention in the abstract itself.

Keywords. Immediately after the abstract, provide a maximum of 6 keywords, to be chosen from the standard list published in the journal (see the Elsevier website at http://elsevier.com/authors. These keywords will be used for indexing purposes.

Abbreviations. Define abbreviations that are not standard in this field at their first occurrence in the article: in the abstract but also in the main text after it. A list of common abbreviations is given in the journal (see the home page), but these abbreviations should be defined in the article, too. Ensure consistency of abbreviations throughout the article.

N.B. Acknowledgements. Collate acknowledgements in a separate section at the end of the article and do not, therefore, include them on the title page, as a footnote to the title or otherwise.

Arrangement of the article

Subdivision of the article. Divide your article into clearly defined and numbered sections. Subsections should be numbered 1.1 (then 1.1.1, 1.1.2, ?), 1.2, etc. (the abstract is not included in section numbering). Use this numbering also for internal cross-referencing: do not just refer to 'the text.' Any subsection may be given a brief heading. Each heading should appear on its own separate line.

Introduction. State the objectives of the work and provide an adequate background, avoiding a detailed literature survey or a summary of the results.

Experimental/Materials and methods. Provide sufficient detail to allow the work to be reproduced. Methods already published should be indicated by a reference: only relevant modifications should be described.

Results. Results should be clear and concise.

Discussion. This should explore the significance of the results of the work, not repeat them. A combined Results and Discussion section is often appropriate. Avoid extensive citations and discussion of published literature.

Conclusions. The main conclusions of the study may be presented in a short Conclusions section, which may stand alone or form a subsection of a Discussion or Results and Discussion section.

Appendices. If there is more than one appendix, they should be identified as A, B, etc. Formulae and equations in appendices should be given separate numbering: (Eq. A.1), (Eq. A.2), etc.; in a subsequent appendix, (Eq. B.1) and so forth.

Acknowledgements. Place acknowledgements, including information on grants received, before the references, in a separate section, and not as a footnote on the title page.

References. See separate section, below.

Figure legends, tables, figures, schemes. Present these, in this order, at the end of the article. They are described in more detail below. If you are working with LaTeX and have such features embedded in the text, these can be left, but such embedding should not be done specifically for publishing purposes. Further, high-resolution graphics files must be provided separately (see Preparation of illustrations ).

Text graphics. Present incidental graphics not suitable for mention as figures, plates or schemes at the end of the article and number them 'Graphic 1', etc. Their precise position in the text can then be defined similarly (both on the manuscript and in the file). See further under the section, Preparation of illustrations . If you are working with LaTeX and have such features embedded in the text, these can be left, but such embedding should not be done specifically for publishing purposes. Further, high-resolution graphics files must be provided separately (see Preparation of illustrations ).

Specific remarks

Mathematical formulae. Present simple formulae in the line of normal text where possible. In principle, variables are to be presented in italics. Use the solidus (/) instead of a horizontal line,

e.g., Xp/Ym rather than

Powers of e are often more conveniently denoted by exp. Number consecutively any equations that have to be displayed separate from the text (if referred to explicitly in the text).

Footnotes. Footnotes should be used sparingly. Number them consecutively throughout the article, using superscript Arabic numbers. Many wordprocessors build footnotes into the text, and this feature may be used. Should this not be the case, indicate the position of footnotes in the text and present the footnotes themselves on a separate sheet at the end of the article. Do not include footnotes in the Reference list.
Table footnotes. Indicate each footnote in a table with a superscript lowercase letter.

Tables. Number tables consecutively in accordance with their appearance in the text. Place footnotes to tables below the table body and indicate them with superscript lowercase letters. Avoid vertical rules. Be sparing in the use of tables and ensure that the data presented in tables do not duplicate results described elsewhere in the article.

Nomenclature and units. Follow internationally accepted rules and conventions: use the international system of units (SI). If other quantities are mentioned, give their equivalent in SI. You are urged to consult IUPAC: Nomenclature of Organic Chemistry and Inorganic Chemistry ( http://www.iupac.org/) for further information.

Preparation of supplementary data. Elsevier now accepts electronic supplementary material to support and enhance your scientific research. Supplementary files offer the author additional possibilities to publish supporting applications, movies, animation sequences, high-resolution images, background datasets, sound clips and more. Supplementary files supplied will be published online alongside the electronic version of your article in Elsevier web products, including ScienceDirect: http://www.sciencedirect.com. In order to ensure that your submitted material is directly usable, please ensure that data is provided in one of our recommended file formats. Authors should submit the material in electronic format together with the article and supply a concise and descriptive caption for each file. For more detailed instructions please visit the Elsevier website at http://elsevier.com/authors

This journal offers electronic submission services and supplementary data files can be uploaded via the Elsevier website at http://elsevier.com/authors

References

Responsibility for the accuracy of bibliographic citations lies entirely with the authors.

Citations in the text: Please ensure that every reference cited in the text is also present in the reference list (and vice versa). Any references cited in the abstract must be given in full. Unpublished results and personal communications should not be in the reference list, but may be mentioned in the text. Citation of a reference as ′in press′ implies that the item has been accepted for publication.

Citing and listing of web references. As a minimum, the full URL should be given. Any further information, if known (author names, dates, reference to a source publication, etc.), should also be given. Web references can be listed separately (e.g., after the reference list) under a different heading if desired, or can be included in the reference list. Text: Indicate references by number(s) in square brackets in line with the text. The actual authors can be referred to, but the reference number(s) must always be given.

Example: "..... as demonstrated [3,6]. Barnaby and Jones [8] obtained a different result ...."

List: References should be listed alphabetically, typed in the same format as the main text, preferably in the same was as the following examples:

1. [1] E. Borger, Computability, Complexity, Logic (North-Holland, Amsterdam, 1989).
2. [2] D.E. Knuth, Theory and [Practice, Theoret. Comput. Sci. 90 (1991) 1-15.
3. [3] A.K. Lenstra and H.W. Lenstra, Jr., Algorithms in number theory, in: J. van Leeuwen, ed., Handbook of Computer Science, Vol. A, Elsevier, Amsterdam, 1990, pp. 673-715.
4. [4] M. Li, Lower bounds by Kolmogorov complexity, in: Proc. ICALP'85, in: Lecture Notes in Computer Science, Vol. 194, Springer, Berlin, 1985, pp. 383-393.
5. [5] A. Rajasekar, Semantics for logic programs, Ph.D. Thesis, Department of Computer Science, University of Maryland, 1989.
   
   

PREPARATION OF ILLUSTRATIONS

Preparation of electronic illustrations

Submitting your artwork in an electronic format helps us to produce your work to the best possible standards, ensuring accuracy, clarity and a high level of detail.

General points

• Always supply high-quality printouts of your artwork, in case conversion of the electronic artwork is problematic.
• Make sure you use uniform lettering and sizing of your original artwork.
• Save text in illustrations as "graphics" or enclose the font.
• Only use the following fonts in your illustrations: Arial, Courier, Helvetica, Times, Symbol.
• Number the illustrations according to their sequence in the text.
• Use a logical naming convention for your artwork files, and supply a separate listing of the files and the software used.
• Provide all illustrations as separate files and as hardcopy printouts on separate sheets.
• Provide captions to illustrations separately.
• Produce images near to the desired size of the printed version.

A detailed guide on electronic artwork is available on our website: http://elsevier.com/artworkinstructions

You are urged to visit this site; some excerpts from the detailed information are given here.

Formats
Regardless of the application used, when your electronic artwork is finalised, please "save as" or convert the images to one of the following formats (Note the resolution requirements for line drawings, halftones, and line/halftone combinations given below.):

EPS: Vector drawings. Embed the font or save the text as "graphics".
TIFF: Colour or greyscale photographs (halftones): always use a minimum of 300 dpi.
TIFF: Bitmapped line drawings: use a minimum of 1000 dpi.
TIFF: Combinations bitmapped line/half-tone (colour or greyscale): a minimum of 500 dpi is required.
DOC, XLS or PPT: If your electronic artwork is created in any of these Microsoft Office applications please supply "as is".

Please do not:

• Supply embedded graphics in your wordprocessor (spreadsheet, presentation) document;
• Supply files that are optimised for screen use (like GIF, BMP, PICT, WPG); the resolution is too low;
• Supply files that are too low in resolution;
• Submit graphics that are disproportionately large for the content.
  
  

Non-electronic illustrations

Provide all illustrations as high-quality printouts, suitable for reproduction (which may include reduction) without retouching. Number illustrations consecutively in the order in which they are referred to in the text. They should accompany the manuscript, but should not be included within the text. Clearly mark all illustrations on the back (or - in case of line drawings - on the lower front side) with the figure number and the author's name and, in cases of ambiguity, the correct orientation.

Mark the appropriate position of a figure in the article.

Captions

Ensure that each illustration has a caption. Supply captions on a separate sheet, not attached to the figure. A caption should comprise a brief title (not on the figure itself) and a description of the illustration. Keep text in the illustrations themselves to a minimum but explain all symbols and abbreviations used.

Line drawings

Supply high-quality printouts on white paper produced with black ink. The lettering and symbols, as well as other details, should have proportionate dimensions, so as not to become illegible or unclear after possible reduction; in general, the figures should be designed for a reduction factor of two to three. The degree of reduction will be determined by the Publisher. Illustrations will not be enlarged. Consider the page format of the journal when designing the illustrations.

Photocopies are not suitable for reproduction. Do not use any type of shading on computer-generated illustrations.

Photographs (halftones)

Please supply original photographs for reproduction, printed on glossy paper, very sharp and with good contrast. Remove non-essential areas of a photograph. Do not mount photographs unless they form part of a composite figure. Where necessary, insert a scale bar in the illustration (not below it), as opposed to giving a magnification factor in the legend.

Note that photocopies of photographs are not acceptable.

Colour illustrations

Submit colour illustrations as original photographs, high-quality computer prints or transparencies, close to the size expected in publication, or as 35 mm slides. Please make sure that artwork files are in an acceptable format (TIFF, EPS or MS Offices files) and with the correct resolution. Polaroid colour prints are not suitable. If, together with your accepted article, you submit usable colour figures then Elsevier will ensure, at no additional charge, that these figures will appear in colour on the web (e.g., ScienceDirect and other sites) regardless of whether or not these illustrations are reproduced in colour in the printed version. Please indicate your preference for colour on the web (free of charge) or in print and on the web (charged) when submitting your article. For colour reproduction in print, you will receive information regarding the costs from Elsevier after receipt of your accepted article. For further information on the preparation of electronic artwork, please see http://elsevier.com/artworkinstructions.

Please note: Because of technical complications which can arise by converting colour figures to 'grey scale' (for the printed version should you not opt for colour in print) please submit in addition usable black and white versions of all the colour illustrations.

Proofs

When your manuscript is received by the Publisher it is considered to be in its final form. Proofs are not to be regarded as 'drafts'.

One set of page proofs in PDF format will be sent by e-mail to the corresponding author, to be checked for typesetting/editing. No changes in, or additions to, the accepted (and subsequently edited) manuscript will be allowed at this stage. Proofreading is solely your responsibility.

A form with queries from the Copyeditor may accompany your proofs. Please answer all queries and make any corrections or additions required.

The Publisher reserves the right to proceed with publication if corrections are not communicated.

Return corrections within 2 days of receipt of the proofs. Should there be no corrections, please confirm this.

Elsevier will do everything possible to get your article corrected and published as quickly and accurately as possible. In order to do this we need your help. When you receive the (PDF) proof of your article for correction, it is important to ensure that all of your corrections are sent back to us in one communication. Subsequent corrections will not be possible, so please ensure your first sending is complete. Note that this does not mean you have any less time to make your corrections, just that only one set of corrections will be accepted.