5 things you need to know Tuesday

1. Happy birthday, Mr. President

It's President Obama's big day, and he's sharing it with start-up entrepreneurs during the first Demo Day at the White House on Tuesday. At the event, venture capitalists will announce their commitment to advancing women and minorities' business opportunities, a move forward Obama has spoken about. People started celebrations for the president — who turns 54 — early Monday with a serenade from young African leaders and a president's staff tweet inviting people to sign a birthday card. The celebrations also come one day after announcing his climate change plan to reduce emissions 32% by the year 2030, relative to 2005 levels starting in 2017.

2. Fox to announce top 10 candidates for first GOP debate

With 18 candidates vying for the GOP presidential nomination, Fox News will cut that pool to 10 on Tuesday for the first Republican presidential debate to be held this week. Fox, which will host the event with Facebook in Cleveland on Thursday, will average the five most recent polls from "major, nationally recognized organizations that use standard methodological techniques." For the candidates who don't make the top spots, a smaller debate will be held several hours before the main event. And the methodology for choosing candidates doesn't go without drama: Former IRS commissioner Mark Everson, a GOP candidate, filed a complaint with the Federal Election Commission on Monday, alleging that he has been unfairly excluded from the debate.

3. World's best hackers take over Las Vegas

Professional hackers will hide their credit cards, smartphones and laptops starting Tuesday at the Black Hat security conference in Las Vegas. With upwards of 9,000 security executives, hackers, academics, government and law enforcement staffers, professionals will stay vigilant against hackers attending and won't use local Wi-Fi or Bluetooth to communicate. Topics at the conference will cover security trends and new technologies to combat hacking, like guaranteeing security when using network-connected firearms and understanding the future of hacking into cars. Pre-convention security classes started on Aug. 1.

4. Sentencing phase begins in trial of Colo. theater shooter

The final phase is set to begin in the trial of James Holmes, who killed 12 and injured 70 in a shooting at a crowded movie theater in the Denver suburbs three years ago. Jurors have already convicted the 27-year-old former University of Colorado neuroscience researcher of first-degree murder, and Monday they took less than three hours to reject any mitigating factors put forward by the defense to rule out the death penalty. Emotional testimony is expected from victims and families who will argue in favor of the death penalty before the jurors make their sentencing decision. If a single juror decides against the death penalty, Holmes will be sentenced to life in prison.

5. Silicon Valley couple to pledge $40 million investment in tech diversity

Longtime Silicon Valley diversity advocates Mitch Kapor and wife Freada Kapor Klein will invest $40 million over three years in a set of initiatives designed to give women and underrepresented minorities a better shot at becoming technology entrepreneurs. They will make the announcement Tuesday during the first White House Demo Day, which will showcase technologies from the nation's diverse entrepreneurs and kick off a new initiative to bring greater diversity to the tech world. These initiatives come as members of the Congressional Black Caucus are in Silicon Valley to turn up the heat on the nation's largest tech companies to hire more African-American workers.

And, the essentials:

Weather: A slow-moving cold front will trigger showers and storms across much of the East.

Stocks: Greek stock markets are suffering a second day of losses Tuesday, while U.S. stock futures are lower.

TV Tonight: Wondering what to watch tonight? TV critic Robert Bianco looks at the CMA Music Festival, JFK & LBJ: A Time for Greatness and Back on Board: Greg Louganis.

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