Edit in JSFiddle

$("body:first").parent().attr("xmlns:m","http://www.w3.org/1998/Math/MathML");

function updateModule(course) {
    var query = "";
    query += "SELECT * ";
    query += "FROM xml ";
    query += "WHERE url='http://cnx.org/content/" + course + "/latest/body' ";
    //console.log("query=" + query);
    var yql = "";
    yql += "http://query.yahooapis.com/v1/public/yql?q=";
    yql += encodeURIComponent(query);
    yql += "&format=xml";
    yql += "&callback=?";
    //console.log("yql=" + yql);
    $.getJSON(yql, function(data) {
        //console.dir(data.results[0]);
        $course = $(data.results[0]);

        $("#xml").val(data.results[0]);

        $("#here").html(data.results[0]);
        $("img:not([src^='http'])").each(function() {
            $(this).attr("src", "http://cnx.org/content/" + course + "/latest/" + $(this).attr("src"));
        });

        MathJax.Hub.queue.Push(["Typeset", MathJax.Hub]);
    });
}

$("#module").change(function() {
    var course = $(this).val();
    updateModule(course);
});

updateModule($("#module option:first").val());

<script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js">
    MathJax.Hub.Config({
        config: ["MMLorHTML.js"],
        jax: ["input/TeX","input/MathML","output/HTML-CSS","output/NativeMML"],
        extensions: ["tex2jax.js","mml2jax.js","MathMenu.js","MathZoom.js"],
        TeX: {extensions: ["AMSmath.js","AMSsymbols.js","noErrors.js","noUndefined.js"]}
    });
</script>

<h1>Select a ConneXions Module</h1>
<select id="module" name="module">
    <option value="m0050">The Sampling Theorem</option>
    <option value="m0051">Amplitude Quantization</option>
    <option value="m0052">Summary of Series and Parallel Combination Rules</option>
    <option value="m0053">Dependent Sources</option>
    <option value="m0054">Using Operational Amplifiers</option>
    <option value="m0055">Inverting Amplifier</option>
    <option value="m0056">Inverting Amplifiers with Impedances</option>
    <option value="m0057">Designing Circuits with Operational Amplifiers</option>
    <option value="m0058">Diode Behavior</option>
    <option value="m0059">Logarithmic Amplifier</option>
</select>

<br/><hr/><br/>

<h1>Body Content</h1>
<div id="here"></div>

<br/><hr/><br/>

<h1>Client Side XML Representation</h1>
<textarea id="xml" cols="70" rows="100"></textarea>