Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Following Monday's losses, stocks opened slightly lower today, with the S&P 500 and the narrower, price-weighted Dow Jones Industrial Average (DJINDICES:^DJI) down 0.16% and 0.32%, respectively, at 10:15 a.m. EST.

Shares of Apple (NASDAQ:AAPL) are up 1.9%, testing the 2013 closing high of $556.07 they achieved last Friday, as two significant pieces of news regarding the iPhone maker hit the market this morning.

First, in a validation of the rise of Twitter's influence, Apple has acquired social-media analytics firm Topsy Labs for more than $200 million. Topsy's tools help to make sense of the roughly 500 million daily tweets by analyzing topics, terms, or hashtags on a historical or real-time basis, identifying influential users and measuring the effectiveness of an event or campaign.

Those capabilities could be relevant to several of Apple's existing applications, with analysts mentioning the iTunes media store, the Siri voice assistant, and the iAd advertising platform as the most likely candidates. The latter, in particular, which sells ads within mobile apps on the iPhone and iPad, has met with limited success since it was introduced in 2010.

Sure, social networking is a huge trend, but I'm quite confident this is the second piece of news that is really driving Apple's stock higher today. Indeed, Apple may well have landed the big fish in its campaign for expansion in growth markets, with Fortune reporting late yesterday that a website belonging to a subsidiary of China Mobile (NYSE:CHL) -- located in Suzhou, a city of 5 million west of Shanghai -- began taking pre-orders for the iPhone 5s and 5c, the latest additions to the iPhone range.

Although the reservation page has since been taken down, its initial appearance suggests that Apple and China Mobile have inked a broader distribution deal -- a deal that will have taken six years to put together. With nearly 760 million customers, China Mobile is the world's largest mobile-phone operator. If that isn't enough to convey the size of the opportunity, consider that China Mobile added nearly 50 million customers on a net basis this year, or roughly one-third of the total number of smartphone users in the U.S.

Apple is setting its sights on China, with the launch of the iPhone 5s and 5c marking the first time China was included in the first wave of countries to receive the latest iteration of the iPhone. That has helped Apple achieve the fifth spot in terms of market share with 6%, leapfrogging local manufacturers Xiaomi and ZTE.

Fool contributor Alex Dumortier, CFA has no position in any stocks mentioned. The Motley Fool recommends Apple. The Motley Fool owns shares of Apple and China Mobile. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.