Latex refers generically to a stable dispersion (emulsion) of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic. Latex as found in nature is the milky sap of many plants that coagulates on exposure to air. It is a complex emulsion in which proteins, alkaloids, starches, sugars, oils, tannins, resins and gums are found. In most plants, latex is white, but some have yellow, orange, or scarlet latex.

The word also refers to the thin stretchy material obtained by processing the sap (see Latex clothing, below). It can also be made synthetically by polymerizing a monomer that has been emulsified with surfactants.

Sources

The cells or vessels in which latex is found make up the laticiferous system, which forms in two very different ways. In many plants, the laticiferous system is formed from rows of cells laid down in the meristem of the stem or root. The cell walls between these cells are dissolved so that continuous tubes, called latex vessels, are formed. This method of formation is found in the poppy family, in the rubber trees (Para rubber tree and Castilla elastica), and in the Cichorieae, a section of the Family Asteraceae distinguished by the presence of latex in its members. Dandelion, lettuce, hawkweed and salsify are members of the Cichorieae. It is also present in another member of the Asteraceae, the guayule plant.

In the milkweed and spurge families, on the other hand, the laticiferous system is formed quite differently. Early in the development of the seedling latex cells differentiate, and as the plant grows these latex cells grow into a branching system extending throughout the plant. In the mature plant, the entire laticiferous system is descended from a single cell or group of cells present in the embryo.

The laticiferous system is present in all parts of the mature plant, including roots, stems, leaves, and sometimes the fruits. It is particularly noticeable in the cortical tissues.

Natural function of latex

Many plant functions have been attributed to latex. Some regard it as a form of stored food, while others consider it an excretory product in which waste products of the plant are deposited. Still others believe it functions to protect the plant in case of injuries; drying to form a protective layer that prevents the entry of fungi and bacteria. Similarly, it may provide some protection against browsing animals, since in some plants latex is very bitter or even poisonous. It may be that latex fulfills all of these functions to varying degrees in the numerous plant species in which it occurs.

Uses of latex

Latex has many commercial uses, from clothing to paint. Male condoms are commonly made of latex. Synthetic latex is not flammable and has little odor. As well as its use in clothing, synthetic latex can be cured to form a dry film and is used as a binder in latex paint. Natural latex is used in the manufacturing of latex mattresses using the Talalay Process, beauty application pads, and cushioning, but natural latex decomposes when exposed to the elements, turning rapidly to dust.

The latex of many species can be processed to produce other materials. Natural rubber is the most important product obtained from latex; more than 12,000 plant species yield latex containing rubber, though in the vast majority of those species the rubber is not suitable for commercial use.^[1] Balatá and gutta percha latex contain an inelastic polymer related to rubber. Latex from the chicle and jelutong trees is used in chewing gum.

Poppy latex is a source of opium and its many derivatives.

Some people have a serious latex allergy, and exposure to latex or rubber products such as rubber gloves can cause anaphylactic shock. As latex has a protein found also in bananas, care should be taken to ensure people are not allergic to both. Guayule latex is hypoallergenic and is being researched as a substitute to the allergy-inducing Hevea latexes.

Latex clothing

:

Latex is used in many types of clothing. It is different from rubber in that it is less refined and often thinner. Worn on the body (or applied directly by painting) it tends to be skin-tight, producing a "second skin" effect. It has a shinier finish than rubber.

Latex mattresses

Latex is used in the manufacturing of many types of mattresses such as sofas and beds.

Allergic reactions

Latex can cause an allergic reaction:
Latex allergy

Notes

See also

• Dental dam

External links

• Latex Allergy and Sensitivity
• Latex Allergies

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LaTeX is a document markup language and document preparation system for the TeX typesetting program. Within the typesetting system, its name is styled as .

LaTeX is widely used by mathematicians, scientists, philosophers, engineers, scholars in academia and the commercial world, and other professionals.^[2] As a primary or intermediate format (e.g. translating DocBook and other XML-based formats to PDF), LaTeX is used because of the quality of typesetting achievable by TeX. The typesetting system offers programmable desktop publishing features and extensive facilities for automating most aspects of typesetting and desktop publishing, including numbering and cross-referencing, tables and figures, page layout and bibliographies.

LaTeX is intended to provide a high-level language that accesses the power of TeX. LaTeX essentially comprises a collection of TeX macros and a program to process LaTeX documents. Because the TeX formatting commands are very low-level, it is usually much simpler for end-users to use LaTeX.

LaTeX was originally written in the early 1980s by Leslie Lamport at SRI International ^[3]. It has become the dominant method for using TeX—few people write in plain TeX any more. The current version is LaTeX2e (styled ).

LaTeX, like TeX, is free software.

The typesetting system

LaTeX is based on the idea that authors should be able to focus on the meaning of what they are writing without being distracted by the visual presentation of the information. In preparing a LaTeX document, the author specifies the logical structure using familiar concepts such as chapter, section, table, figure, etc., and lets the LaTeX system worry about the presentation of these structures. It therefore encourages the separation of layout from content while still allowing manual typesetting adjustments where needed. This is similar to the mechanism by which many word processors allow styles to be defined globally for an entire document or the CSS mechanism used by HTML.

LaTeX can be arbitrarily extended by using the underlying macro language to develop custom formats. Such macros are often collected into packages, which are available to address special formatting issues such as complicated mathematical content or graphics. There are numerous commercial implementations of the entire TeX system. System vendors may add extra features like additional typefaces and telephone support. LyX is a free visual document processor that uses LaTeX for a back-end. TeXmacs is a free, WYSIWYG editor with similar functionalities as LaTeX but a different typesetting engine.

A number of popular commercial desktop publishing systems use modified versions of the original TeX typesetting engine. The recent rise in the popularity of XML systems and the demand for large-scale batch production of publication-quality typesetting from these systems and other sources has seen a steady increase in the use of LaTeX.

The example below shows the LaTeX input:

>
\documentclass[12pt]{article}
\title{\LaTeX}
\date{}
\begin{document}
\maketitle \LaTeX{} is a document preparation system for the \TeX{}
typesetting program. It offers programmable desktop publishing
features and extensive facilities for automating most aspects of
typesetting and desktop publishing, including numbering and
cross-referencing, tables and figures, page layout, bibliographies,
and much more. \LaTeX{} was originally written in 1984 by Leslie
Lamport and has become the dominant method for using \TeX; few
people write in plain \TeX{} anymore. The current version is
\LaTeXe.
\newline
% This is a comment, it is not shown in the final output.
% The following shows a little of the typesetting power of LaTeX
\begin{eqnarray}
E &=& mc^2                              \    m &=& \frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}}
\end{eqnarray}
\end{document}

This input would produce the following LaTeX output:



Example from Online LaTeX /.

Pronouncing and writing "LaTeX"

LaTeX is usually pronounced [ˈleɪ.tɛk] or [ˈlɑ.tɛk] in English (that is, not with the [ks] pronunciation English speakers normally associate with X, but with a [k]). The last character in the name comes from a capital Χ (chi), as the name of TeX derives from the Greek τέχνη (skill, art, technique); for this reason, TeX's creator Donald Knuth promotes a /tɛx/ pronunciation (that is, with a voiceless velar fricative as in Modern Greek, or the last sound of the Scottish word "loch" or the German word "Bach", similar to the Spanish "j" or Arabic "خ" sounds). Lamport, on the other hand, has said he does not favor or discourage any pronunciation for LaTeX.

The name is traditionally printed with the special typographical logo shown on this page. In media where the logo cannot be precisely reproduced in running text, the word is typically given the unique capitalization LaTeX to avoid confusion with the word “latex”.

Licensing, implementations, and distributions

LaTeX is typically distributed along with plain TeX. It is distributed under a free software license, the LaTeX Project Public License (LPPL). The LPPL is not compatible with the GNU General Public License, as it requires that modified files also modify the actual physical file names; this was done to ensure that files that depend on other files will produce the expected behavior and avoid dependency hell. A new version of the LPPL that will be compatible with the GPL is under development. The LPPL is DFSG compliant as of version 1.3. As free/open source software, LaTeX is available on most operating systems including Linux, Unix, Windows, Mac OS X and AmigaOS. It is noteworthy to mention that the first DVI previewers capable of on-screen previewing and modification of LaTeX documents were Amigas^[1][2].

As a Macro package, LaTeX provides a set of macros for TeX to interpret. There are many for TeX, including Plain TeX, GNU Texinfo, AMSTeX, and ConTeXt.

When TeX "compiles" your document, the processing loop (from the user's point of view) goes like this: Macros > TeX > Driver > Output. Different implementations of each of these steps is typically available in TeX distributions. Traditional TeX will output a DVI file, which is usually converted to a PostScript file. More recently, Hàn Thế Thành and others have written a new implementation of TeX called pdfTeX, which also outputs to PDF and takes advantages of features available in that format. The XeTeX engine developed by Jonathan Kew merges modern font technologies with TeX.

The default font for LaTeX is Knuth's Computer Modern, which gives most documents created with LaTeX the same distinctive look and feel as those created with plain TeX.

A number of TeX distributions are available, including TeX Live (multiplatform), teTeX (deprecated, Unix), fpTeX (deprecated), MiKTeX (Windows), MacTeX, gwTeX (Mac OS X), OzTeX (Mac OS Classic), AmigaTeX (no longer available) and PasTeX (AmigaOS) available on Aminet repository.

Versions

LaTeX2e is the current version of LaTeX. As of 2007, a future version called LaTeX3 is in development. Planned features include improved syntax, hyperlink support, a new user interface, access to arbitrary fonts, and new documentation.^[4]

Notes

1. ^ : In 1986 Tomas Rokicki printed his first page with dvisw, an early DVI printer driver for the Amiga, on a QMS SmartWriter using AmigaTeX by Radical Eye Software. A link to a relic info about milestones of LaTeX history is available at this external site.
2. ^ : Description of Amiga system used by Tomas Rokicki in an article on TUG official review Tugboat: TUGboat, volume 9, (1998) n.1; Site Reports "The Commodore Amiga: A Magic Machine" by Tomas Rokicki, also available in PDF format at this external site

References

External links

• Official LaTeX project site website for open development of LaTeX (has links to and documentation for LaTeX2e and to experimental prerelease code which may be used in LaTeX3)
• CTAN – The Comprehensive TeX Archive Network Latest (La)TeX-related packages and software
• The UK TeX FAQ maintained by Robin Fairbairns
• The TeX Users Group has extensive links to other information, including meetings, conferences, typesetting, the TUGboat journal, and local user groups in many countries