BlueReZZ

<?xml version="1.0" encoding="UTF-8"?>

<item xmlns="http://libero.pub" xmlns:jats="http://jats.nlm.nih.gov" xmlns:xlink="http://www.w3.org/1999/xlink">

    <meta>

        <id>demo-launch-post</id>
        <service>scholarly-articles</service>

    </meta>

BlueReZZ

    public class XmlStripper
    {
        public XmlNode RemoveAllNamespaces(XmlNode documentElement)
        {
            var xmlnsPattern = "\\s+xmlns\\s*(:\\w)?\\s*=\\s*\\\"(?<url>[^\\\"]*)\\\"";
            var outerXml = documentElement.OuterXml;
            var matchCol = Regex.Matches(outerXml, xmlnsPattern);
            foreach (var match in matchCol)
                outerXml = outerXml.Replace(match.ToString(), "");