jQuery not defined

Hope someone can help. I want use jQuery on my pages, but just cannot get it to work properly. I have enqueued my script and jQuery in my themes function.php file based on instructions in these tutorials.
http://wp.tutsplus.com/articles/how-to-include-javascript-and-css-in-your-wordpress-themes-and-plugins/
http://wpcandy.com/teaches/how-to-load-scripts-in-wordpress-themes/#.UtXAAnlBRUs

I know my script is loading as it it logging some things to the console. However, and I can see that query has been loaded from my server in the developer tools… However – jQuery functions I am calling are having no effect, and further more if I try to access jQuery from the developer tools interpreter I get:

ReferenceError: jQuery is not defined

What am I doing wrong?

Here is my code in my functions.php:

// Let's hook in our function with the javascript files with the wp_enqueue_scripts hook 

add_action( 'wp_enqueue_scripts', 'ddd_load_scripts' );

// Register some javascript files, because we love javascript files. Enqueue a couple as well 

function ddd_load_scripts() {
  if (!is_admin()) {
  	wp_enqueue_script( 'jquery' );
	  wp_register_script( 'headscript', get_theme_root_uri()."/DDD2014/js/headscript.js");
	  wp_enqueue_script( 'headscript' );
	}
}

and an example of my js:
jQuery(“#aboutpop”).css({ opacity: 0.5 });